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A study of dark adaptation in ocular hypertensives using a two-filter method Patton, Danalee Goldthwaite 1972

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i A STUDY OF DARK ADAPTATION IN OCULAR HYPERTENSIVES USING A TWO-FILTER METHOD by DANALEE GOLDTHWAlTE PATTON B.A. , U n i v e r s i t y o f P e n n s y l v a n i a , 1966 A THESIS SUBMITTED•IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n t he Department of P s y c h o l o g y We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE.UNIVERSITY OF BRITISH COLUMBIA September, 1972 In present ing th is thes is in p a r t i a l f u l f i l m e n t of the requirements fo r an advanced degree at the Un ive rs i t y of B r i t i s h Columbia, I agree that the L i b r a r y sha l l make i t f r e e l y a v a i l a b l e for reference and study. I fu r ther agree that permission for extensive copying of th is t h e s i s for s c h o l a r l y purposes may be granted by the Head of my Department or by h is representa t i ves . It is understood that copying or p u b l i c a t i o n o f th is t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my wr i t ten permiss ion . Department of The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8. Canada Date J W - /, (473— i i ABSTRACT Dark adaptation thresholds have been determined for a group of'ocular hypertensives and a group of equivantly aged normal.controls under two separate conditions'of colored pre-adaptation and test. The method relies on the Purkinje shift to obtain two dark adap-tation curves for each subject that cross when the i n i t i a l l y favored long wavelength .(yellow) curve i s superceded by the shorter one (blue-green): under photopic conditions, the yellow and blue-green stimuli are equally efficient in stimulating the retina, _;as they are equated for brightness during pre-adaptation; as dark adaptation proceeds the blue-green and yellow thresholds display >an early relation wherein yellow light has the lower thresholds; then the curves, cross and blue-green light displays lower thresholds. Each curve i s obtained separately with a pre-adaptation of 80 f t . lamberts for 5 minutes and a centrally fixated 11° test patch that matches the spectral composition of the pre-adaptation. A variety of variables are derived from threshold intensity measurements and they are analyzed for age effects, disease effects, and their interactions. Age and disease both depress blue-green and yellow cone sensitivity, delay cross-over time, and increase the total change in sensitivity over 13 minutes of dark adaptation. Interactions magnify differences. Color discrimination is found to be associated with dark adaptation thresholds, sometimes specifically as to the type of color defect and the i i i c o l o r e d d a r k a d a p t a t i o n c u r v e s h o w i n g l o s s e s . . I n t r a o c u l a r p r e s s u r e , m a c u l a r s e n s i t i v i t y , a n d d i a s t o l i c b l o o d p r e s s u r e a r e a l s o s i g n i f i c a n t l y c o r r e l a t e d w i t h d a r k a d a p t a t i o n t h r e s h o l d s : D i s e a s e a n d a g e e f f e c t s a r e e l a b o r a t e d i n t e r m s o f c h a n g e s i n t h e o c u l a r m e d i a , m a c u l a r p i g m e n t a t i o n c h a n g e s , a s w e l l a s d e t e r i o r a t i o n o f r o d a n d c o n e p r o c e s s e s . I n a d d i t i o n , a g i n g i s s e e n t o b e c o m p l i c a t e d b y p e c u l i a r i t i e s i n t h e s e l e c t i o n o f t h e n o r m a l p o p u l a t i o n . T h e a s s o c i a -t i o n s d e m o n s t r a t e d f o r c l i n i c a l a n d c o l o r v i s i o n v a r i a b l e s w i t h d a r k a d a p t a t i o n t h r e s h o l d s s u g g e s t ( I ) t h a t o p e n a n g l e g l a u c o m a m a y b e c a u s e d b y d e f i c i e n t n u t r i t i o n t o t h e o p t i c n e r v e h e a d o r t o t h e r e t i n a i t s e l f , ( 2 ) t h a t c e n t r a l r o d a n d c o n e v i s i o n u n d e r g o c h a n g e s v e r y e a r l y i n t h e c o u r s e o f t h e d i s e a s e . A p r e l i m i n a r y s t u d y u s i n g t h e t w o - f i l t e r m e t h o d w i t h w e l l - e s t a -b l i s h e d g l a u c o m a c o n f i r m s t h a t s i m i l a r , m o r e p r o n o u n c e d l o s s e s i n d a r k a d a p t a t i o n t a k e p l a c e l a t e r i n t h e d i s e a s e ' s d e v e l o p m e n t . i v TABLE OF CONTENTS Page I INTRODUCTION . 1/ II REVIEW OF THE LITERATURE 4 A. , Pre-Adaptation Intensity and Duration -4* B. Pre-Adaptation Pattern, Size, and Location ..... .#8 C. - The effects of Pre-Adaptation and Test Color on Dark-Adaptation 22 D. Testfield Location, Size, and Duration. .. ... E. Pupil Diameter . ..-.: ;• 37 F. Age and Dark-Adaptation -. J41 G. Glaucoma and Dark-Adaptation ..... 4'5 H. Glaucoma and Dark-Adaptation ..... • 5/1 I. Dark-Adaptation in the Color Anomalous ...... 53j J. Mechanism of Dark-Adaptation ..... <55 III OBJECTIVES OF THIS STUDY A. General Considerations ..... ^64 B. • The Theoretical Framework ..... (66 IV APPARATUS ..... '78 V PROCEDURE .;. .. &% VI ANALYSIS OF THE EXPERIMENTAL RESULTS '9-4 A. • Sta t i s t i c a l Considerations ...... l9-4 r B. The Present Study as an Independent Investigation '101 C. Summary and Preliminary Discussion ..... /-155 D. Additional Comparisons with the Lakowski, Bryett, and Drance Study ..... 1-65 E. Dark-Adaptation and C l i n i c a l Variables ..... /1-7/1 VII DISCUSSION 175' VIII BIBLIOGRAPHY 1,87/ IX APPENDIX A. Tables I-V • 1 9 9 B. A Technique for Re-painting Photometric Spheres ^ 1.5 > V LIST OF TABLES Page I . N i n e s t u d i e s d e s i g n e d t o e x p l o r e t h e e f f e c t o f p r e - a d a p t a t i o n i n t e n s i t y v a r i a t i o n a t c o n s t a n t fi d u r a t i o n s ..... 199 I I . The e f f e c t s o f p r e - a d a p t a t i o n s i z e and r e t i n a l l o c a t i o n on d a r k - a d a p t a t i o n : , v a l u e s o f t h e v a r i a b l e s i n t h r e e e x p e r i m e n t s 200-I I I . : The e f f e c t s o f p r e - a d a p t a t i o n and t e s t c o l o r on d a r k - a d a p t a t i o n ..... 201 IV. ' Age and D a r k - A d a p t a t i o n ....... 203 V. Glaucoma and Dark A d a p t a t i o n ..... 205 J V I . ; D e s i g n o f t h e E x p e r i m e n t ..... 96 V I I . D i s t r i b u t i o n o f the Normal and E y p e r t e n s i v e P o p u l a t i o n s ...... 103 V I I I . A c u i t y Comparisons Between C o n t r o l s and H y p e r t e n s i v e s ...... 1 04 I X . A. Normals ( s p l i t by age). . .... 10.8 B. H y p e r t e n s i v e s ( s p l i t by age) 109 C. Normals compared t o H y p e r t e n s i v e s . ( s p l i t by age) 110 D. Age D i f f e r e n c e s . ( w i t h i n n o r m a l s and h y p e r t e n s i v e s ) . . : . . 1 1 I1' X. Comparisons Between t h e P r e s e n t Study and t h e L a k o w s k i , B r y e t t , and Drance Study - 149' X I . R e l a t i o n Between the H y p e r t e n s i v e P o p u l a t i o n s : t h e L a k o w s k i , B r y e t t and Drance P o p u l a t i o n Compared t o t h e P r e s e n t One 166' X I I . R e l a t i o n Between t h e H y p e r t e n s i v e P o p u l a t i o n s : t h e L a k o w s k i , B r y e t t add Drance P o p u l a t i o n Compared t o t h e P r e s e n t One ..... 167*"' v l LIST OF FIGURES Page 1. T y p i c a l dark adaptation curves f o r d i f f e r e n t i n t e n s i t i e s of pre-adaptation at a constant d u r a t i o n . 6 • 2. The n o n - r e c i p r o c i t y of cones and r e c i p r o c i t y of rods as pre-exposure time i s r a i s e d and I lowered ...... 1 3' ^ 3. P e r i p h e r a l dark adaptation curves w i t h white pre-adaptation and seven t e s t o o l o r s ..... 232 1 4. Average p e r i p h e r a l dark adaptation curves f o r four color-normal subjects a f t e r white p r e -adaptation and s i x t e s t c o l o r s ...... 241'11 5. • Dark adap ta t ion w i t h a v i o l e t 1621 mu-Vand a yell o w t e s t l i g h t f o l l o w i n g pre-adaptation to four c o l o r s • 2§S 6. Real energy spectrum s e n s i b i l i t y curves f o r rod and cone v i s i o n . . .'.-. 27* ' 7. R e t i n a l d e n s i t y gradients f o r rods and cones ..... - 34'. 8. Drainage route i n the normal eye 45 9. D i s r u p t i o n of normal drainage routes i n open and closed angle glaucoma - 46 < ;i-10. Scotopic (S) and Photopic (P) curves of r e l a t i v e luminous e f f i c i e n c y - 69 ' 11. S p e c t r a l s e n s i t i v i t y curves • 70 • 12. S p e c t r a l energy d i s t r i b u t i o n s f o r pre-adapta-t i o n and t e s t 81 13. Bridgman's C1953). account of mesopic t h r e s h o l d r e l a t i o n s i n dark adaptation ..... 83? 14. The subject-generated dark adaptation curve ...... 8 § ; v i i L i s t o f F i g u r e s ( c o n t ' d ) Page 15. I l l u m i n a t i o n s c h e d u l e f o r d a r k a d a p t a t i o n t e s t i n g 9 2 ^ ' 16. D i s t r i b u t i o n o f t h e n o r m a l and h y p e r t e n s i v e p o p u l a t i o n s -1 02- ! 17. Dark a d a p t a t i o n c u r v e s f o r t h e n o r m a l and h y p e r t e n s i v e p o p u l a t i o n s A. young n o r m a l s , o l d n o r m a l s ..... 1 1.2. B. young h y p e r t e n s i v e s , o l d h y p e r t e n s i v e s 116 C. o l d n o r m a l s compared to o l d h y p e r t e n s i v e s , young n o r m a l s compared t o young h y p e r t e n -s i v e s 120 D. Age d i f f e r e n c e s w i t h i n n o r m a l s age d i f f e r e n c e s w i t h i n h y p e r t e n s i v e s ..... 1 28 -18. C r o s s - o v e r t i m e s and i n t e n s i t i e s f o r n o r m a l s and h y p e r t e n s i v e s 138 19. C r o s s - o v e r t i m e s and i n t e n s i t i e s i n r e l a t i o n r , t o age 139 20. D i s t r i b u t i o n o f s c o r e s f o r t h e I s h i h a r a ..... 147 21. Comparison between v o l u n t e e r and r e f e r r e d n o r m a l s u b j e c t s 152 22. N o r m a l , h y p e r t e n s i v e , and g l a ucoma.curves ' 18© 23. Normal da r k a d a p t a t i o n t h r e s h o l d c u r v e s + 2.S.D. and t h e f i v e worse h y p e r t e n s i v e s u b j e c t s ' c u r v e s 183•' v i i i ACKNOWLEDGEMENTS I would l i k e t o than k : - Dr. R. L a k o w s k i f o r a s s i s t a n c e and.encouragement i n most a s p e c t s o f t h i s work. - Dr.. S t e v e n M. Drance f o r p e r m i s s i o n t o t e s t h i s p a t i e n t s and - J u l i a B r y e t t f o r s e t t i n g u p . a p p o i n t m e n t s w i t h them. - J o h n S u t h e r l a n d f o r c o n s t r u c t i o n o f t h e s e l f - t e s t i n g a p p a r a t u s . - K e i t h O l i v e r f o r t h e e x e c u t i o n o f sane o f the f i g u r e s , and a s s i s -t a n c e i n t h e computer programming.-- M r s . K.O. Waldron f o r . t y p i n g t h e f i n a l m a n u s c r i p t . 1 INTRODUCTION Absolute visual thresholds depend on, among other things, the retina'S's previous history of stimulation. If the eye is illuminated, then plunged into darkness, the threshold i s seen to decrease, and i t does so over a period of time. Since 1865 when Aubert f i r s t described these events and applied the term "adaptation" to them, much information has accumulated relating the parameters of i n i t i a l illumination and subsequent threshold measure-ment; in addition, since antiquity, variations in dark adaptation have been attributed to pathological conditions. The purpose of this investi-gation i s to look for dark adaptation losses i n an early diseased condi-tion with the intention of uncovering deterioration in a part of the . retina usually thought.of as free of c l i n i c a l changes u n t i l late in the course of the disease. The disease under examination i s open angle glau-i . . coma, and i t s i i n i t i a l stage is characterized by increased pressure within the eyeball. Results stemming from research on color discrimination among hypertensive eyes suggests that there are indeed heretofore.- overlooked losses i n visual functioning at the fovea, although there was a great deal of evidence for foveal color vision losses among patients with esta- blished glaucoma before the color vision experiments in hypertensives were undertaken, just as dark adaptation dysfunction had been documented 2 f o r c e n t r a l v i s i o n a m o n g g l a u c o m a s b e f o r e t h e p r e s e n t s t u d y w a s b e g u n . T h e t e c h n i q u e u s e d h e r e c a n ^ i n o n e s e n s e r b e v i e w e d a s d e p e n d e n t ' o n , o r r e l a t e d t o , c o l o r v i s i o n p r o c e s s e s b e c a u s e i f r e t i n a l i l l u m i n a t i o n a n d d a r k a d a p t a t i o n m e a s u r e m e n t s a r e d o n e w i t h c o l o r e d l i g h t . T h e p r o c e -d u r e w a s f i r s t u s e d s u c c e s s f u l l y b y G i l l ( 1 9 6 0 ) o n a g r o u p o f d i a b e t i c p a ^ f e i ' e n t ' s ; " h e d e s c r i b e d t h e n a t u r e o f n o r m a l d a r k a d a p t a t i o n u n d e r t h e s e c o n -d i t i o n s , a s w e l l a s c h a n g e s i n i t r e s u l t i n g f r o m a g e . T h e p r e s e n t s t u d y c a n b e s e e n , t h e n , , a s a n a t t e m p t t o c o n f i r m h i s f i n d i n g s . I n a d d i t i o n , i t i s d e s i r a b l e t o r e l a t e n e w i n f o r m a t i o n a b o u t o c u l a r h y p e r t e n s i o n a n d d a r k a d a p t a t i o n t o t h e o l d e r l i t e r a t u r e w i t h a v i e w t o -w a r d s o r t i n g o u t t h e d i s c r e p a n c i e s t h a t h a v e d e v e l o p e d o v e r t h e y e a r s . T o s o m e e x t e n t t h i s s t u d y w a s s u c c e s s f u l i n d o i n g s o . T h e p r i n c i p l e d e p e n d e n t v a r i a b l e i n d a r k a d a p t a t i o n i s t h r e s h o l d i n t e n s i t y . A v a r i e t y o f d e r i v e d v a r i a b l e s c a n b e c o m p u t e d f r o m t h e t h r e s h o l d i n t e n s i t y v s . t i m e - i n - t h e - d a r k c u r v e t h a t r e s u l t s ; t h e y a r e . o n o n e l e v e l , d e s c r i p t i o n s o f t h e c u r v e s , b u t o n a n o t h e r , t h e y a r e a t t r i b u t a b l e t o t h e v i s u a l p r o c e s s e s t h a t d e t e r m i n e t h e m . A n a l y s i s o f t h e r e s u l t s c a n b e r e -s o l v e d i n t o b o t h l e v e l s , a l t h o u g h t h e s e c o n d o n e i s n e c e s s a r i l y i n t h e r e a l m o f s p e c u l a t i o n . E x t r a i n f o r m a t i o n f r o m c l i n i c a l o p h t h a l m o l o g i c a l t e s t s j a s w e l l a s c o l o r v i s i o n t e s t s w a s . a v a i l a b l e , a n d w h e n a n a l y z e d i n r e l a t i o n t o d a r k 3 adap ta t ion measurements, i t permi t s hypotheses about glaucoma mechanisms to be fo rmula ted . But more i m p o r t a n t l y , i t c o n t r i b u t e s to an atmosphere o f urgency regard ing what k inds and l o c a t i o n s o f d e t e r i o r a t i o n and^at .what stage of the d i sease fu ture research should d i r e c t i t s e f f o r t . 4 I I REVIEW OF THE LITERATURE A-. . ' E r e - A d a p t a t i o n I n t e n s i t y a n d ' D u r a t i o n Most o f t e n , experiments have s t u d i e d the e f f e c t of i n t e n s i t y and d u r a t i o n of the p r e - a d a p t i n g s t i m u l u s t o g e t h e r . At the o u t s e t , however, i t i s prudent to c o n s i d e r what happens when i n t e n s i t i e s are v a r i e d under c o n d i t i o n s of constant d u r a t i o n , and when d u r a t i o n s are v a r i e d under c o n d i -t i o n s of constant i n t e n s i t y . Table I summarizes the ranges of i n t e n s i t i e s a long w i t h c o n d i t i o n s of constant d u r a t i o n f o r n i n e s t u d i e s . I t i g n o r e s o ther v a r i a b l e s such as r e t i n a l p o s i t i o n , c o l o r , d u r a t i o n , and area of the t e s t p a t c h , and presence of a f i x a t i o n p o i n t . For t h i s r e a s o n , e i t h e r c o n c l u s i o n s about the e f f e c t of p r e - a d a p t a t i o n i n t e n s i t y should be g e n e r a l enough so as to remain t r u e i r r e g a r d l e s s of the extraneous c o n d i t i o n s , or the v a r i a t i o n i n the c o n d i t i o n s not i n c l u d e d i n the t a b l e ought to some e x t e n t , be made r e s p o n s i b l e f o r except ions i n the g e n e r a l p o i n t s about i n t e n s i t y . I n s p i t e of the v e r y great range of i n t e n s i t i e s and d u r a t i o n s em-ployed across these s t u d i e s and ' / r e g a r d l e s s of the v a r i a b l e c o n d i t i o n s of p r e - a d a p t a t i o n and t e s t i n g , the r e s u l t s are i n agreement on s i x p o i n t s : (1) the h i g h e r the p r e - a d a p t a t i o n i n t e n s i t y the h i g h e r the i n i t i a l t h r e s h o l d . (2) a t h i g h e r i n t e n s i t i e s the dark a d a p t a t i o n curve i s i n two p a r t s — a n i n i t i a l s e c t i o n a t t r i b u t a b l e to cone a d a p t a t i o n , 5 and a l a t e r s e c t i o n a t t r i b u t a b l e t o r o d a d a p t a t i o n ; a t l o w e r i n t e n s i t i e s pure r o d c u r v e s a r e o b t a i n e d . (3) A s h i f t i n t i m e f o r t h e appearance o f a . g i v e n t h r e s h o l d o c c u r s as i n t e n s i t y changes; t h e s h i f t f o r r o d s i s g r e a t e r t h a n t h e s h i f t f o r cones. (4) - A t h i g h e r i n t e n s i t i e s n o t o n l y do d a r k a d a p t a t i o n c u r v e s have t h e same shape, b u t t h e t i m e s h i f t f o r t h e appearance of a g i v e n t h r e s h o l d d e c r e a s e s ( i . e . , t h e d e l a y i n r e c o v e r y as i n t e n s i t y i s i n c r e a s e d i s n o t so p r o n o u n c e d ) ; a t t h e v e r y h i g h e s t i n t e n s i t i e s c u r v e s have a f i x e d shape and t h e r e i s no t i m e s h i f t as i n t e n s i t y i s r a i s e d . There i s some s u g g e s t i o n i n two p a p e r s ( C r a i k and V e r n o n , 1941, and H a i g i 1941) t h a t s i m i l a r e f f e c t s a r e t o be f o u n d a t v e r y l o w i n t e n s i t i e s . (5) The s l o p e o f t h e r o d and cone p o r t i o n s o f t h e d a r k a d a p t a t i o n c u r v e d e c r e a s e s as p r e - a d a p t a t i o n i n t e n s i t y i s i n c r e a s e d ; t h e appearance o f t h e r o d . p o r t i o n i s d e l a y e d w i t h i n c r e a s i n g i n t e n s i t y . (6) A t h i g h e r i n t e n s i t i e s t h e r o d c u r v e m a i n t a i n s an a l m o s t c o n -s t a n t s l o p e ( i . e . , i s a l m o s t l i n e a r ) from i t s b e g i n n i n g ; a t l o w e r i n t e n s i t i e s t h e s l o p e d e c r e a s e s d u r i n g t h e f i r s t m i n -u t e s ( i . e ,t> i s n o n - l i n e a r ) . F i g u r e 1 summarizes t h e s e s i x p o i n t s g r a p h i c a l l y . Not e a c h o f the n i n e s t u d i e s o b t a i n s both, cone and r o d c u r v e s f o r 6 7 various reasons. The use of a red test patch 1 in area at the fovea will favor cone curves to the exclusion of rod curves.(Mote and Riopelle, 1951); the use of a violet test patch in the periphery favors.rod curves even at higher pre-adaptation intensities (Haig, 1941). Because duration of pre-adaptation,is not without its own influence, i t was possible for Windsor and Clark (1936) to get cone curves at 5 min. pre-adaptation while Wald and Clark (1937) got only rod curves at 5 sec. of the same pre-adaptation intensity. Crawford's data (1947) fails to show a clear rod-cone break, possibly because unlike most experimenters he didn't employ a fixation point. MacLeod and Bartlett (1954) have provided some independent confir-mation of intensity effects by varying the traditional measure of dark adaptation. If reaction time to a test patch of constant intensity is plotted against time in the dark the curv e is seen to f a l l more quickly for lower pre-adaptation intensities. Baker (1953) gives evidence to. support the idea that an analogous phenomenon exists at the neural level. If threshold measurements are taken before the pre-adaptation light is extinguished a rise appears before dark-ness begins, then the curve falls. The peak's position on the time axis is related to pre-adaptations intensity, occurring before darkness onset for cone curves and simultaneous with darkness onset for rod curves (i.e. lower pre-adaptation intensity). The existence of the rise and £ts janticipatory aspect can be accounted for by.appealing to relative latencies of near-8 threshold responses and responses to stimulus cessation (Crawford, 1947), and response depression following stimulus decrease. The analysis is complex, but i t implies that acotopic systems may involve shorter re-sponse latencies to near-threshold stimuli, or longer response latencies to stimulus cessation, or less response depression following a stimulus decrease, or a l l three, than photopic systems. Three of the nine papers in Table T include data on the effect of changing durations of pre-adatation under conditions of constant intensity- (Mote and Riopelle, 1951; Wald and Clark, 1937; Haig, 1941).. ^Mote'and Riopelle used four constant intensities (565, 1130, 5650, 11300 mL) at each of three durations (30, 150, 300 sec.) to obtain cone curves. Wald and Clark looked at 1890 ml at 10 sec. and 5 sec. Haig examined rod curves at 447 mL for 0.1, 0,4j 1, 2, 4, 6 and 10 min. of pre-adapta-tion. A l l these studies tend to confirm the idea that changes in duration at constant intensities have the same effect on-the course of dark adap-. tation as ..do changes in intensity at constant durations. Thus Mote and Riopelle found that as duration of pre-adaptation is increased the i n i -t i a l cone threshold rises, the slope decreases, and the time to reach a certain threshold increases. Haig obtained' similar results for rod curves" and pointed out that above.a certain duration C4 -min. i n his ex-periment) further increases cease to change the curve characteristics. (Mote and Riopelle's results for cone curves at comparable intensities 9 don't have durations beyond five min. so i t ' s not p o s s i b l e to s a y . i f Haig's observations could be gen e r a l i z e d to cones). I t i s i n t e r e s t i n g i n t h i s - connection to n o t i c e that Wald and Cl a r k ' s C1937) curves confirm Haig's conclusions i s that at 1890 mL a doubling of exposure time doesn't r a i s e the i n i t i a l t h r e s h o l d , b u t " i t does delay the appearance of the rod p o r t i o n of the curve and g e n e r a l l y i t slows adaptation. The c o n f l i c t w i t h Haig's data may be due to the e f f e c t of the very much higher i n t e n s i -ty used b y W a l d and Cl a r k . This l a s t p o i n t i l l u s t r a t e s the kinds of r e s u l t s that a r i s e when i n t e n s i t y and du r a t i o n are v a r i e d together so as to r e v e a l the e f f e c t s of t h e i r i n t e r a c t i o n w i t h each other. The simplest r e l a t i o n s h i p i n t e n s i t y and d u r a t i o n could have would be f o r an increase i n i n t e n s i t y to compen-sate f o r a decrease i n du r a t i o n and v i c e v e r s a ; the r e t i n a would f a i l to d i s c r i m i n a t e between a c o n d i t i o n whereby i t received a l a r g e amount of l i g h t over a short p e r i o d of time arid one whereby i t . r e c e i v e d a smaller amount of l i g h t over a longer p e r i o d of time as long as i n t e n s i t y x time = constant ( I x t = C). I f the r e t i n a d i d detect a d i f f e r e n c e i n the two co n d i t i o n s of exposure ( i . e . , i f the r e c i p r o c i t y of i n t e n s i t y and d u r a t i o n broke down) we might expect to o b t a i n d i f f e r e n c e s i n dark adaptation curves under c o n d i t i o n s where t = C. Experimenters agree that the r e c i p r o c i t y law doesn't always f£t the f a c t s , but j u s t where i t f a i l s to hold i s a matter f o r some d i s c u s s i o n , as is- the r e l a t i v e importance of 1 as compared to t i n a n o n T r e c i p r o c i t y s i t u a t i o n . 10 Wald and Clark L937) concluded that rod dark adaptation after short pre-adaptation is more rapid than after long exposures even i f intensity i s adjusted to compensate. They had noted that for a total pre-adatation of 18900 mL-sec. incorporating a brief- exposure time, dark adaptation was actually faster than for a total pre-adaptation of 12600 mL-sec. incorporating a long exposure time. Haig's (1941) more extensive investigation resulted in curves conflicting with Wald and Clark's data. He found that up to t = 4 min. when I x t = C, the rod dark adaptation curves are identical i f slope and time to.reach, a given threshold are the c r i t e r i a for identity. Be-yond four minutes, i f curves with equal i n i t i a l thresholds are super-imposed, they, are found*£b coincide even tfeugh. the total pre-exposures (in mL-sec.) are not the same. Crawford (1946) shed some light on the problems raised by Wald and Clark and Haig by suggesting that reciprocity i s a property of rods (therefore, scotopic) and nonSreciprocity i s a property of cones (there-fore, photopic). The duration of pre-adaptation, except at very high 2 intensities CL0.000 c/ft ) seems to determine whether rods or cones w i l l operate. When cones are functional intensity does indeed " f a i l to com-pensate", because as duration is increased and intensity decreased (always meeting the.'X'"x t = C condition), higher intensities produce curves showing slower adaptation. At very high intensities cones.operate irregardless of the duration i f i t is above 0.03 sec. The c r i t i c a l ' '<•. 11 d u r a t i o n ( I . e . , the ti m e beyond w h i c h t h e r e c i p r o c i t y r e l a t i o n s h i p b r e a k s 2 down) i s under 3 s e c . f o r i n t e n s i t i e s b e l o w 10.000 c / f t . . T h i s c r i t i c a l d u r a t i o n compares u n f a v o r a b l y w i t h H a i g ' s 4 m i n . , p r o b a b l y because H a i g ' s use o f a v i o l e t t e s t l i g h t v i r t u a l l y e l i m i n a t e d t h e p o s s i b i l i t y o f cone p a r t i c i p a t i o n i n t h r e s h o l d d e t e r m i n a t i o n s e x c e p t f o r v e r y l o n g d u r -a t i o n s . Wald and C l a r k r e a c h d i f f e r e n t c o n c l u s i o n s about r o d r e c i p r o c i t y p o s s i b l y because.what t h e y t a k e t o Be r o d c u r v e s a r e a c t u a l l y ccne c u r v e s . I n any c a s e , t h e i r r o d c u r v e s a r e o b t a i n e d a t t o t a l p r e - a d a p t a t i o n s com-p a r a b l e t o t h o s e C r a w f o r d s u g g e s t s produce cone c u r v e s . A s e r i e s o f s t u d i e s by Mote e t a l . , (Mote and R i o p e l l e , 1951; Mote, G r a n t , and Hoffman, 1961, Mote and R i o p e l l e , 1953) f i t n i c e l y i n t o C r a w f o r d ' s ' i n t e r p r e t a t i o n w i t h m i n o r q u a l i f i c a t i o n s : They f i n d t h a t knowledge o f t h e t o t a l p r e - a d a p t a t i o n ( i n mL-sec.) i s i m p o r t a n t i n p r e -d i c t i n g t he amount o f r e c i p r o c i t y among d a r k a d a p t a t i o n c u r v e s , and t h i s p o i n t - i s i m p l i c i t i n Cr a w f o r d ' s d a t a : a t l o w e r t o t a l p r e - a d a p t a t i o n s t h e r e i s a g r e a t e r l i k e l i h o o d o f f i n d i n g r e c i p r o c i t y a t l o w d u r a t i o n s when I x t = C. But t h e major c o n t r i b u t i o n o f t h e Mote e t a l . p a p e r s i s t h e i r i l l u s t r a t i o n o f t h e i m p o r t a n t r o l e t h a t t h e ran g e s o f i n t e n s i t y and d u r -a t i o n play- i n r e s t r i c t i n g t h e c o n c l u s i o n s ' t o he drawn f r o m any s m a l l c o l l e c t i o n o f e x p e r i m e n t s , for i n s t a n c e , t h e y f i n d t h a t a t t o t a l p r e -a d a p t a t i o n s j u s t s l i g h t l y h i g h e r t h a n C r a w f o r d ' s . t h e cone a d a p t a t i o n 12 c u r v e s become r e c i p r o c a l . S i m i l a r l y , a l t h o u g h t h e i n i t i a l t h r e s h o l d i s most s e n s i t i v e t o t h e i n t e n s i t y when r e c i p r o c i t y f a i l s , t h e y concede t h a t a t l o n g e r d u r a t i o n s and l o w e r . i n t e n s i t i e s t h e d u r a t i o n may be j u s t as i m p o r t a n t a v a r i a b l e . > ( T h i s i s t h e f o r c e o f Wald and C l a r k ' s • p a p e r , and C r a w f o r d has a t l e a s t two c a s e s t h a t argue f o r an e f f e c t o f d u r a t i o n ) . The u s u a l r e s u l t i s t h a t when t h e l o w i n t e n s i t y / h i g h d u r a t i o n p r e - a d a p t a -t i o n i s g r e a t e r t h a n o r e q u a l t o t h e h i g h i n t e n s i t y / T o w d u r a t i o n p r e -a d a p t a t i o n , t h e h i g h i n t e n s i t y / l o w d u r a t i o n c u r v e has t h e h i g h e r i n i t i a l t h r e s h o l d . The t i m e t o r e a c h . f i n a l t h r e s h o l d i s a n o t h e r v a r i a b l e t h o u g h t b y Mote e t a l . t o be more i n f l u e n c e d by i n t e n s i t y t h a n d u r a t i o n , b u t t h e y c a u t i o n t h a t a t l o n g e r d u r a t i o n s t h i s may n o t be t r u e . C r a w f o r d ' s c u r v e s , i n f a c t , show d u r a t i o n e f f e c t s a t d u r a t i o n s c omparable t o o r l o w e r t h a n Mote e t a l / s , b u t o n l y i n f o v e a l a r e a s , s u g g e s t i n g t h a t i t may be a cone phenomenon. Wolf and Z i g l e r (1954) a n a l y s e d i n more d e t a i l t h e s o u r c e o f cone n o n - r e c i p r o c i t y a n d . i n c i d e n t a l l y p r o v i d e d a r e a s o n f o r f r e q u e n t d i s -c r e p a n c i e s i n r o d i n i t i a l t h r e s h o l d s where r e c i p r o c i t y h o l d s t h r o u g h o u t the r e s t o f t h e c u r v e . Cone f i n a l t h r e s h o l d s a r e i n s e n s i t i v e t o d u r a t i o n changes, y e t v e r y s e n s i t i v e t o i n t e n s i t y changes; t h u s t h e c< *-point has a p o s i t i o n o n .the i n t e n s i t y s c a l e t h a t i s n o n - r e c i p r o c a l w i t h r e g a r d t o i n t e n s i t y and d u r a t i o n . Moreover, t h e . - r p o i n t ' s . l o c a t i o n on t h e t i m e s c a l e i s more s e n s i t i v e t o d u r a t i o n t h a n t o i n t e n s i t y , o c c u r i n g e a r l i e r as d u r a t i o n i s d e c r e a s e d . F i g u r e 2 shows g r a p h i c a l l y why i t w o u l d be 13 time in the dark ik-c dotted Lint t's ttst of tf*<- ro*C Curve \ anttj StO'd ((ties fro\/(d* tknsko(#C measurements . Ce>ri<c Curve <3 ts -6At rssu£f 0-f lowering -Z" e\*«t. Hist rig t tokifc. ktefKstj Meir froctuct same OS-fhl product t-AneCt for A . ft%< open circle e'< d ibresArfiC mtASurcmtnt wrongly 'ttffrifafeaC reefs 14 p o s s i b l e to o b t a i n a lower i n i t i a l t h r e sho ld as t i s i nc reased and I decreased.under c o n d i t i o n s where I x t = C, and yet there i s o n l y one rod curve . S ince i t i s easy to -mistake cone th resho lds f o r rod th resho lds .near the break , what i s c a l l e d an i n i t i a l rod t h r e s h o l d may a c t u a l l y be a p l a t e a u i n g cone t h r e s h o l d , R e c i p r o c i t y has been i n v e s t i g a t e d f o r r e l a t i v e l y more complex s i t u a t i o n s i n v o l v i n g i m p o s i t i o n of a d d i t i o n a l l i g h t adap ta t i on on a r e t i n a that has a l r eady been .comple te ly adapted to a c e r t a i n b r i g h t n e s s l e v e l (Johannsen, M c B r i d e , and Wulfeck , 1956; Wulfeck, Johannsen and M c B r i d e , I960, Hanson, Anderson, and Win te rbe rg , 1960). Por low i n t e n s i -ty l e v e l s and low t o t a l pre-exposure l e v e l s (up to 100 :. f t .L - sec ) o f superimposed l i g h t , f o v e a l dark adap ta t ion curves f o r eyes a l r e a d y adapted to the dark or to low b r igh tnes s l e v e l s don ' t d i f f e r from curves r e s u l t i n g from i n i t i a l adap ta t ion o n l y . P e r i p h e r a l areas have lower to l e rances f o r superimposed l i g h t a d a p t a t i o n , but l i k e the f o v e a l a reas , i n t e n s i t y and .du ra t i on above and below the t o l e r ance l e v e l s are r e c i p r o -c a l , at l e a s t fo r the ranges i n v e s t i g a t e d . I n t e r m i t t e n t p r e - adap t a t i on to l i g h t adds yet another c o m p l i c a -t i o n to the r e c i p r o c i t y r e l a t i o n . Hanson et a l . (Hanson, Anderson, and Win te rbe rg , I960) compared dark adaptat ion, curves r e s u l t i n g from a l i g h t o n - l i g h t o f f p r e - adap t a t i on c o n d i t i o n s f o r which I x t = C. The i n i t i a l th resho lds gave evidence f o r r e c i p r o c i t y , but the times to f i n a l t h r e s h o l d d i d n o t . Al thouglLaLl i n t e r m i t t e n t c o n d i t i o n s r e s u l t i n g i n t o t a l p r e -adapta t ions that were equ iva l en t to each other f e l l below an equ iva l en t 15 continuous pre-adaptation, the long duration/low i n t e n s i t y intermittent condition produced delayed dark adaptation curves compared to the short duration/high i n t e n s i t y intermittent•condition. This i s another case of . i n t e n s i t y f a i l i n g to compensate for duration. Mote et a l . (Mote, and Reed, 1952) confirmed Hanson et a l ' s , r e s u l t s f o r intermittent pre-adaptations l a s t i n g more than three min. Below three min. intermittent conditions follow a r e c i p r o c i t y law, which i s not s u r p r i s i n g since both Hanson et a l . and Adair C1953) noticed that when I x t = C and lower t o t a l intermittent pre-adaptations are used dark adaptation curves become-more nearly- s i m i l a r (i.e.^,when the ligh-dark cycles are not c a r r i e d on very long). This same point was made before i n connection with simple continuous conditions of pre-adaptation. llote'and Reed (1952a,b) and Adair (1953) wondered i f compensating for the los s of the l i g h t time that characterizes an intermittent pre-adapta-t i o n by increasing the i n t e n s i t y of such a pre-adaptation instead of i t s durations-would r e s u l t i n dark adaptation curves resembling the continu-ous equivalent pre-adaptation dark adaptation curve. Intermittent pre-adaptation had always resulted i n curves f a l l i n g below continuous pre-adaptation curves, but intermittent pre-exposures equivalent to continu-ous ones had always-'entered the experimental design as-.increases' in the length of time light-dark, cycles were presented (Hanson, Anderson, and Winterberg, I960; 'Mote'and Reed, 19525:). In t e n s i t y compensation does indeed produce ;dark.adaptation curves that coincide with curves from a 16 continuous control,, and even with curves f ran other intermittent condi-tions having equivalent total pre-adaptations. : For low intensities, compensation by duration increases results in i n i t i a l thresholds that are either equal to the controls' (Mote and Reed) or lower (Hanson, Anderson, and Winterberg), and an adaptation speed that i s either slower (Mote and Reed) or faster (Hanson, Anderson, and Winterberg). For high intensities, a decrease in light time • (and consequently compensation by duration increases) gives a lower, faster curve (Mote and Reed). Hanson et a l . get different results at low intensities probably because their light-dark cycles covered many seconds and Mote et al.'s always, occured within a second. It . i s d i f f i c u l t to say anything general about these last studies except that dark adaptation seems more sensitive to pre-adaptation dura-tion than to intensity irregardless of the mode (continuous or discontin-uous) of light presentation. But once again, ,the Hanson e t a l . experiment cautions against saying anything more specific because intensity and duration ranges as well,as periodicity of intermittence mustbe ; taken into -account f i r s t . Baker, Debons, and Morris (1956) concluded'that different combina-tions of intensity and area i n preadaptation, as long as the total amount of l i g h t i s held'constant, produce no important changes in dark adaptation curves. ' The only deviations from a reciprocity relation they 17 a t t r i b u t e . t o a "Mote and Reed e f f e c t " ; eye movements cause s i n g l e r ecep -to r s to r e c e i v e i n t e r m i t t e n t s t i m u l a t i o n dur ing p r e a d a p t a t i o n e s p e c i a l l y when s m a l l f r a c t i o n s of the t o t a l f i e l d are i l l u m i n a t e d ' ; u n l e s s the i n ^ t e n s i t y i s r a i s e d beyond the l e v e l at w h i c h i t w i l l compensate f o r area decreases , d a r k . a d a p t a t i o n curves fo r high, i l l u m i n a t i o n of s m a l l f rac t tons-of the t o t a l p r e - adap t a t i on f i e l d w i l l f a l l be low curves f o r low i l l u m i n a -t i o n of l a r g e r f r a c t i o n s - - ^ p r e - adap t a t i on c o n d i t i o n more n e a r l y l i k e con- , t inuous exposure from a s i n g l e r e c e p t o r ' s p o i n t of v i e w . 18 B. • P r e - A d a p t a t i o n P a t t e r n , S i z e , and L o c a t i o n We c o u l d make t h e B a k e r , Debons, and M o r r i s c o n c l u s i o n even more g e n e r a l b y s a y i n g t h a t no m a t t e r b y what c o m b i n a t i o n o f i n t e n s i t y and l i g h t - d a r k d i s t r i b u t i o n a r e t i n a l a r e a a c h i e v e s a s p e c i f i c i n i t i a l d a r k a d a p t a t i o n t h r e s h o l d , h a v i n g a t t a i n e d i t , i t s r e c o v e r y o f s e n s i t i v i t y as e v i d e n c e by i t s d a r k a d a p t a t i o n c u r v e w i l l be t h e same.. C r a w f o r d , 0-940) t e s t e d e x a c t l y t h i s i d e a as i t r e l a t e s t o i n t e n s i t y and s i z e o f p r e - a d a p t i n g f i e l d s — v a r i a b l e s he c o n s i d e r s t o be•subsumed un d e r t h e g e n e r a l c o n c e p t o f " p a t t e r n " . T a b l e I I summarizes h i s e x p e r i m e n t and two o t h e r s aimed a t r e l a t e d q u e s t i o n s . TYlbst o f t h e t a b l e i s s e l f - e x p l a n a -t o r y , b u t some comment on p r o c e d u r a l d i f f e r e n c e s w i l l c l a r i f y t h e d i s c u s - ' s i o n . • Hanson, A n d e r s o n , and W i n t e r b e r g ' s p e r i p h e r a l l y l o c a t e d t e s t p a t c h e s f a l l e i t h e r o u t s i d e t h e p r e - a d a p t a t i o n f i e l d , j u s t i n s i d e i t , o r w e l l i n s i d e i t . F o r s m a l l e r p r e - a d a p t a t i o n f i e l d s , C r a w f o r d s e t s t h e i r b r i g h t n e s s e s so t h a t b r i g h t n e s s d i f f e r e n c e t h r e s h o l d s between t e s t p a t c h arid p r e a d a p t a t i o n f i e l d a r e f o r a l l s i z e s e q u a l t o one v a l u e , and thu s a l l t h e i n i t i a l d a r k a d a p t a t i o n t h r e s h o l d s a r e e q u a l . W i t h a few.; e x c e p t i o n s , a l l t h r e e e x p e r i m e n t s , i n s p i t e o f t h e i r d i f f e r e n c e s , come up w i t h no e f f e c t o f p r e - a d a p t a t i o n f i e l d s i z e on d a r k a d a p t a t i o n , e i t h e r f o v e a l l y o r p e r i p h e r a l l y . F o r p r e - a d a p t i n g f i e l d s o f 19 e q u a l . s i z e , f o v e a l c u r v e s t r a v e r s e o n l y h a l f t h e number o f l o g u n i t s as do p e r i p h e r a l c u r v e s , b u t t h e r e a r e no d i f f e r e n c e s i n s l o p e . But s u c h a n e a t summary o f r e s u l t s , i s m i s l e a d i n g . I t ' s n o t p a r t i c u l a r l y s u r p r i s i n g t h a t t o o b t a i n e q u a l i n i t i a l t h r e s h o l d s C r a w f o r d can compensate f o r p r e - a d a p t a t i o n : f i e l d s i z e change w i t h f i e l d b r i g h t n e s s , and t h a t B a k e r , Debons, and M o r r i s can a d j u s t f o r f i e l d a r e a changes w i t h . b r i g h t n e s s changes. I n f a c t , i n s p e c t i o n o f C r a w f o r d ' s c u r v e s shows t h a t p r e - a d a p t a t i o n f i e l d a r e a ^ x i n t e n s i t y = a c o n s t a n t , j u s t as p r e - a d a p t a -t i o n l i g h t a r e a x i n t e n s i t y - a c o n s t a n t i n t h e B a k e r , Debons and M o r r i s e x p e r i m e n t , a l t h o u g h t h e whole of C r a w f o r d ' s f i e l d i s i l l u m i n a t e d and B a k e r , Debons, and M o r r i s ' f i e l d i s a d a r k p a t c h w i t h e v e n l y s paced s p o t s of l i g h t . A c o n s i d e r a t i o n of Hanson, A n d e r s o n a n d W i n t e r b e r g ' s c u r v e s , however, r e v e a l s a d i s c r e p a n c y w i t h C r a w f o r d ' s d a t a , f o r as s i z e of p r e - , a d a p t a t i o n f i e l d c h a n g e s ' i n t h e former e x p e r i m e n t . i t ' s n o t n e c e s s a r y t o a d j u s t p r e - a d a p t a t i o n b r i g h t n e s s i n o r d e r f o r d a r k a d a p t a t i o n t o f o l l o w e x a c t l y e q u a l c o u r s e s . T h i s i s t r u e f o r c a s e s i n t h e f o v e a where b r i g h t -n e s s r a n g e s , p r e - a d a p t a t i o n f i e l d s i z e s , and f i x a t i o n c o n d i t i o n s (but n o t p r e - a d a p t a t i o n o r t e s t patch, s i z e , .or t e s t p a t c h . . d u r a t i o n ) o v e r l a p i n t h e two e x p e r i m e n t s . P e r i p h e r a l c o n d i t i o n s a r e l e s s comparable r e g a r d i n g f i x a t i o n , l o c a t i o n , t e s t p a t c h and p r e ^ a d a p t l n g f i e l d d u r a t i o n , ' and t e s t p a t c h s i z e . A p p a r e n t l y the r e t i n a r e c o v e r s ' i t s l i g h t s e n s i t i v i t y i n s u c h a way as t o d i s r e g a r d some a s p e c t s of t h e p a t t e r n o f p r e v i o u s l i g h t 20 s t i m u l a t i o n s ; How complete i s i t s i n d i f f e r e n c e ? I t woul d be i n t e r e s t i n g t o know i f p r e - a d a p t i n g t h e whole r e t i n a as opposed t o some p a r t o f i t r e s u l t s i n d i s s i m i l a r c u r v e s when i n i t i a l d a r k a d a p t a t i o n t h r e s h o l d s a r e made e q u a l . • Would t h e ' B a k e r ^ Debons, and M o r r i s s p o t g r i d g i v e d i f f e r e n t c u r v e s t h a n a f u l l d i s c o r a p a t c h w i t h c o n t i n u o u s l y g r a d e d i n t e n s i t i e s ? The e x c e p t i o n s t o t h e summarized r e s u l t s o f t h e s e p a p e r s add t o the c o m p l e x i t y o f t h e s i t u a t i o n ^ There i s some s u g g e s t i o n i n t h e iCrawfbrd and t h e Hanson, A n d e r s o n , and W i n t e r b e r g c u r v e s t h a t i f p r e -a d a p t i n g f i e l d s i z e i s e q u a l t o o r l e s s t h a n t e s t p a t c h s i z e , s i z e e f f e c t s o f t h e p r e - a d a p t i n g f i e l d appear e i t h e r as l e s s s e n s i t i v i t y l o s s (and c o n s e q u e n t l y enhancedddark a d a p t a t i o n ) o r as a change i n t h e d a r k a d a p t a -t i o n c u r v e shape compared t o c a s e s w h e r e A p r e - a d a p t i n g f i e l d i s much l a r g e r t h a n t h e t e s t p a t c h . We s h o u l d n o t e a l s o t h a t Hanson, A n d e r s o n and W i n t e r b e r g T s " s m a l l " p r e - a d a p t i n g f i e l d s i n t h e p e r i p h e r y . p r o d u c e d l o w e r i n i t i a l d a r k a d a p t a t i o n t h r e s h o l d s and e a r l i e r f i n a l t h r e s h o l d s t h a n t h e " i n t e r m e d i a t e " and " l a r g e " f i e l d s . The e x p l a n a t i o n f o r t h i s l a s t f a c t . i s t h a t i f the t e s t p a t c h s t i m u l a t e s r e t i n a l ^ a r e a s - r n b t . p r e v i ^ V o u s l y p r e ^ a d a p t e d t o l i g h t , d a r k a d a p t a t i o n t h r e s h o l d s w i l l be l o w e r t h a n i f the t e s t pat c h a r e a had been p r e ^ a d a p t e d . T h i s would r e q u i r e t h a t r e c e p t o r s n o t " a c t a t a d i s t a n c e " — ^ t h a t t h e i r t r a n s v e r s e n e u r a l c o n n e c -t i o n s not d e s e n s i t i z e remote u n s t i m u l a t e d a r e a s . And y e t t h e y must a c t at a d i s t a n c e d sometimes, o t h e r w i s e Hanson, A n d e r s o n and W i n t e r b e r g w o u l d n ' t : f i n d improved d a r k a d a p t a t i o n f o r a 1° p r e - a d a p t a t i o n f i e l d 21 compared to a 2 , 5 ° , 5 ° , 1 0 ° , or 3 7 . 5 ° a rea , a l l o f which show no d i f f e r -e n t i a l e f f e c t s on dark adap ta t i on . P o s s i b l y there i s a p re -adap t ing f i e l d s i z e between 1° and 2 . 5 ° tha t max imal ly a f f e c t s , from a d i s t a n c e , the 1° area on the r e t i n a where the t e s t p a t c h f a l l s . F i e l d diameters above t h i s c r i t i c a l one wou ldn ' t f u r t he r c o n t r i b u t e to the d e - s e n s i t i z i n g process because the a d d i t i o n a l r ecep to r s i n v o l v e d would be too f a r away from the t e s t p a t c h a r e a . Between 1° and . the c r i t i c a l diameter we might expect to see graded e f f e c t s o f p r e - adap t ing f i e l d s i z e on dark adapta-t i o n . Th i s sketchy sugges t ion i s a long l i n e s developed by Graham, Brown and "Mote " (V i s i cm 'arid V i s u a l P e r c e p t i o n , ed. C H . Graham, F i l e y , 1966 p . 177) to account f o r the e f f e c t s o f t h r e sho ld summation at constant l e v e l s o f a d a p t a t i o n . - The shape changes Crawford ob ta ins f o r curves w i t h p r e -adapt ing f i e l d s between 1 0 . 3 ° and 0 . 1 4 ° might have c r o s s - r e c e p t o r connec-t i o n s as t h e i r cause, a l though the reason i s n ' t apparent . F i n a l l y , t h e r e ' s s t rong reason to b e l i e v e that p re -adap t ing f i e l d s i z e can be d i scovered to i n f l u e n c e dark adap ta t ion i f some or a l l of the v a r i a b l e s i n Table I I a r e . a p p r o p r i a t e l y manipu la ted . Honda found sys temat ic e f f e c t s of s i z e on rod p o r t i o n s of the curves a t h igher t o t a l exposures Cdurat ion x i n t e n s i t y ! than Hanson,. Anderson , and Winterberg or Crawford -used. -Rods are known to have-more i n t e r - c o n n e c t i n g f i b e r s than conesj and they converge on h igher order neurons more e x t e n s i v e l y . 22 C.. The. E f f e c t s o f P r e - A d a p t a t i o n and T e s t C o l o r on Dark- A d a p t a t i o n Because c o l o r ( o r m o r e ' s p e c i f i c a l l y , wavelength.) as i t e f f e c t s d a r k a d a p t a t i o n has o f t e n been approached by i n d i v i d u a l r e s e a r c h e r s (see T a b l e I I I ) i n s u c h a way-as t o make t h e p r e - a d a p t a t i o n / t e s t d i v i s i o n b e -s i d e the p o i n t , t h i s s e c t i o n w i l l c o n s i d e r b o t h f u n c t i o n s t o g e t h e r . G e n e r a l o r i e n t a t i o n t o t h e s u b j e c t i s p r o v i d e d by F i g u r e s .3-5, b u t t h e y f a i l t o convey t h e c o m p l e x i t y of i s s u e s m o t i v a t i n g t h e i r g e n e r a t i o n . W i t h the p o s s i b l e e x c e p t i o n of s t u d i e s done w i t h r e d - p r e - a d a p t a t i o n , most o f the p a p e r s i n T a b l e I I I a r e p r i m a r i l y c o n c e r n e d w i t h t h e n a t u r e o f rod-cone p r o c e s s e s , and c o l o r r e c e p t o r i d e n t i f i c a t i o n ; d a r k a d a p t a t i o n c u r v e s - f i g u r e as t o o l s — m e a n s , n o t , e n d s . And c a p r i c i o u s t o o l s 1 a t t h a t . T h e Z i g l e r , W o l f , and K i n g (1951) and Wolf and Z i g l e r (1955) p a p e r s i l l u s t r a t e t h e p r o c e d u r a l p i t f a l l s o f d a r k a d a p t a t i o n s t u d i e s d e s i g n e d t o answer t h e q u e s t i o n : a r e r o d s and cones - s e n s i t i v e t o u l t r a v i o l e t ? , Rod d a r k -a d a p t a t i o n s e n s i t i v i t y i s d e c r e a s e d a f t e r e x p o s u r e t o 285 mur-410 nju. com-p a r e d t o w h i t e e x p o s u r e , but n o t i f a l o n g \ w a v e l e n g t h t e s t l i g h t i s u s e d , and n o t i f one eye i s W p r e - a d a p t e d w h i l e t h e o t h e r one i s w h i t e p r e -adapted,.and t h e y a r e t e s t e d . a l t e r n a t e l y t h e r e a f t e r . S i m u l t a n e o u s e x p o s u r e and a l t e r n a t e t e s t i n g o f two eyes, a p p a r e n t l y l e d Wald t o c o n c l u d e t h a t UV had no e f f e c t . Cones, on t h e o t h e r hand, show- e f f e c t s . o f TTV p r e - a d a p t a t i o n o n l y i f the t e s t p a t c h i s p r e s e n t e d a g a i n s t a b r i g h t s u r r o u n d i n g , o r i f a f>4 tyhetAC (fart Att&ffiAfi'cn Curt/*S WtM- n>Aif< <pr*-Jta/«f6t£(c,n dnei Sti/en Colors. Jrom (jt'U'((HO tA^en A-or* 2 § £tjure V 20 30 minutes in the dark hotmitl Subjects &i:Mr ivlite prt-a*tytAt,'<m yey Zssf &/oj*s. from $rifiA/ri{(ttf) f- '16 JrAwn Srom CAA.fia*/j , ifV7 , 7-2 5 from Av€tl>dchtUJei(cC,tlrf 8; 7 6 7 6{ 5 III > I I I \ White I ight 621 nm x 1 1 1 1 I I 1 1 \ .-. Ye H o w 1 ight A- • 490 nm ^ ^ ^ ^ ^ ^ 436 ^ nm^^ 621 nm 1 1 1 1 , 1 1 1 i Orange 1ight 520 nm V. V dfifi nm 621 nm \ 0 5 10 15 i l l ! 1 1 1 1 \ Orange-red 1ight \ 590 nm \ -- - -4^6 nm • 621 nm 0 5 10 15 l 1 1 1 time in minutes SoUcHATCny frl-OLttaftA.(rton i ° -four Mot*. 26 blue test light i s used. In the late 40's and early 50's a great deal of controversy raged over the issue of whether pre-adaptation to red light as opposed to white resulted in a faster (i.e., a shorter time to reach a specific threshold) dark adaptation curve. Miles (1943) and Semenoff (1941), along with a few other researchers 'claimed to have shown that intermittent ..light stimulation during dark adaptation actually improved the course of dark adaptation, or at any rate, i t didn't delay i t . Miles (1953) subsequently amended these surprising results in a better experiment from the point of view of tasks expected from the subjects, by showing that darkness compared to red s t i -mulation favors'dark adaptation when a simultaneous monocular differential pre-adaptation i s used. (Zigler, et a l . might have pointed out that an alternate monocular method might show even greater differences than Miles obtained). Semenoff also conceded that the detailed nature of the task required of the subject can produce artifacts—"cheery" red stimulation might lead to enhanced discrimination. It i s now generally accepted that long wavelength pre-adaptation compared to photopically equal white pre-adaptation does in fact, enhance dark adaptation. Hecht and Hsia (1945) have provided an elegant analysis of the reasons in terms of the real energy spectrum sensibility curves for rod and cone vision: (see Figure 6)y white light that i s equivalent i n effectiveness to red light for cones i s ten times too bright for rods. Thus, the red pre-adaptation w i l l show a faster recovery curve, particu-l a r l y in the rod section of the curve compared to photopically equivalent ~~\ 1 1 1 1 1 : 1 — — r VIOLAC effect t/cntsi <« is fA<c 400 ' 500 600 • 700 _1 I I I 1 I : l_ L Wavelength Real entryy specftvm SenWbi'li'lH curves ar>J (one i/iu'on from tttckt t Un'*., f?4s-J 28 white pre-adaptation. Rowland and: SloanC1944) argued along the same lines in an earlier experiment. The above two papers offer alternative explanations for Lowry's C1943) non-conforming results wiich seem to-show that red and white pre-adaptation equated for brightness result in similar dark adaptation curves. Hecht a n d Hsia surmised that his pre-adapting lights were ac-tually 'scotopically equal in brightness and so ought to give similar rod dark adaptation curves; Rowland and Sloan accept the pre-adaptations.as photopically equivalent, but point out that his test light i s located in the' fovea whete rods, which might have been differentially pre-adapted to red and white light, contribute tnsubstantially to threshold measurements. The Hecht-Hsia analysis, in fact, can account for a variety of findings. Crawford (1946) observed that scotopically equal red and green pre-adaptation gave similar rod dark adaptation curves. When MacLeod and Bartlett (1954) measured reaction time to photopically equal blue and white flashes they found equivalent foveal dark adaptation reaction time curves, and separate peripheral rod curves. Hecht, Haig and Chase (1937) failed to get, separate cone curves for violet and red test flashes after white pre-adaptation, probably- because the f i l t e r s were equally efficient in the photopic system. The violet rod curve f a l l s below the red, as ex-pected. Finally, Dodt and Jessen (1961), working with frog ERG, obtained one rod curve preceded by two separate cone curves i f they pre-adapted with scotopically equal orange and blue light, but two rod curves'follow-ing one cone curve i f the orange and blue were photopically equal. 29 There i s one f i n d i n g i n two p a p e r s Semenoff (1941) and S m i t h , F o r r e s t and Dimmick (1955) t h e H e c h t - H s i a e x p l a n a t i o n c a n ' t h a n d l e : t h e o r d e r e d p r e s e r v a t i o n of r e t i n a l s e n s i t i v i t y i n d a r k a d a p t a t i o n i s i n t h e d i r e c t i o n o r a n g e , r e d , b l u e p r e - a d a p t a t i o n , and n o t red,.,orange, b l u e . However, S m i t h e t a l . , e x p r e s s e s some doubt about t h e p h o t o p i c e q u i v a l e n c e o f h i s p r e - a d a p t a t i o n c o l o r s , and Semenoff d o e s n ' t t a b u l a t e h i s i n t e n s i -t i e s i n p h o t o m e t r i c u n i t s a t a l l . Three d i f f e r e n t l i n e s o f i n v e s t i g a t i o n u t i l i z i n g t h e w a v e l e n g t h v a r i a b l e i n d a r k a d a p t a t i o n have r e s u l t e d i n s u g g e s t i o n s about t h e n a t u r e of rod—cone i n t e r a c t i o n . Dodt and J e s s e n ( i 9 6 0 ) exposed f r o g eyes t o v e r y i n t e n s e w h i t e l i g h t and r e c o r d e d d a r k a d a p t a t i o n ERG c u r v e s f o r a r e d t e s t , w h i c h s t i m u l a t e s m a i n l y c a i e s , and a b l u e t e s t , w h i c h s t i m u l a t e s m a i n l y r o d s . The c o u r s e o f t h e r e d c u r v e shows cone s e n s i t i v i t y t o be d e p r e s s e d as t h e b l u e c u r v e moves i n t o t h e r o d phase. L i k e w i s e , L i e (1959) showed t h a t t h e p h o t o c h r o m a t i c i n t e r v a l d u r i n g d a r k a d a p t a t i o n i s g r e a t e r t h a n t h e d i f f e r e n c e between pu r e r o d and,pure cone s e n s i t i v i t y . I n human v i s i o n r o d s d e p r e s s cone a c t i v i t y i n t h e sense t h a t when r o d s dominate t h r e s h o l d -measurements i t ' s n e c e s s a r y . t o r a i s e the t e s t i n t e n s i t y beyond t h e c l a s s i -c a l Cone p l a t e a u f o r c o l o r t o be p e r c e i v e d . Wald (I960 a, b.) i n two p a p e r s which, a r e c e n t r a l t o t h e p r o c e d u r e s i n the' p r e s e n t e x p e r i m e n t proposes- t o a s s e s s q u a n t i t a t i v e l y t h e c o n t r i b u t i o n o f r o d and cone r e s p o n s e s i n t h e d a r k a d a p t a t i o n t h r e s h o l d s e p a r a t i o n of two c o l o r e d t e s t l i g h t s . By s e l e c t i n g two t e s t w a v e l e n g t h s s u c h . t h a t t h e 30 f i r s t ( v i o l e t ) f a v o r s r o d s o v e r c o n e s , and the second ( y e l l o w ) f a v o r s cones o v e r r o d s , he o b t a i n s two d a r k a d a p t a t i o n c u r v e s t h a t c r o s s when s c o t o p i c r e t i n a l s e n s i t i v i t y ( v i o l e t Is a more e f f e c t i v e s t i m u l u s t h a n y e l l o w ) r e p l a c e s p h o t o p i c s e n s i t i v i t y ( y e l l o w i s a more * e f f e c t i v e s t i -m u l u s t h a n v i o l e t ) . He a t t r i b u t e s p a r a l l e l l i s m i n the c u r v e s ( w h i c h e x i s t s to v a r y i n g d e grees a c c o r d i n g t o r e t i n a l l o c a t i o n and t h e d i s t r i -b u t i o n o f r o d s and cones) t o an - e a r l y p u r e cone r e s p o n s e o r a l a t e p u r e r o d r e s p o n s e , and d e p a r t u r e s f r o m p a r l l e l l i s m t o a m i x e d r e s p o n s e i n s p i t e o f Bridgman' s (I960) o b j e c t i o n : t h a t m i x e d r e s p o n s e a r e a s a r e made o f r e s p o n s e s o f cones' o r r o d s t o s m a l l w a v e l e n g t h components o f a complex s t i m u l u s . D i s p u t e s o v e r i n t e r p r e t a t i o n o f t h e c u r v e s , s h o u l d n ' t be a l l o w e d t o overshadow t h e u t i l i t y of t h e p r o c e d u r e : i t i s s i m p l e from t h e p o i n t o f v i e w o f s u b j e c t , e x p e r i m e n t e r , and a p p a r a t u s : i t p r o v i d e s s e v e r a l mea-s u r e s by v i r t u e o f g e n e r a t i n g two c u r v e s , whose r e l a t i v e changes depend on s p e c t r a l s e n s i t i v i t y s h i f t s . Such c o n s i d e r a t i o n s s u g g e s t t h a t t he t e c h n i q u e might be s u i t a b l e f o r c l i n i c a l s t u d i e s . The l a s t f j y e p a p e r s i n T a b l e I I I a r e c o n c e r n e d w i t h i d e n t i f y i n g t h e s p e c t r a l s e n s i t i y i t y o f v a r i o u s , c o n e s , and f a l l i n t o two g r o u p s : TYIandelbaum and M i n t z (19411, Hanson and An d e r s o n (I960), and Wald and A u e r b a c h (1955), Auerbach. and Wald (1954), Das ( 1964).At t h e o u t s e t i t s h o u l d be made c l e a r t h a t none.of t h e e x p e r i m e n t s a r e s t r i c t l y c omparable because methods and v a l u e s o f i n d e p e n d e n t ' v a r i a b l e s d i f f e r s i g n i f i c a n t l y . Wald and A u e r b a c h (1955), f o r i n s t a n c e , a r e . c o n c e r n e d t o p o i n t o u t t h a t 31 t h e i r r e s u l t s may be d i f f e r e n t p a r t l y because t h e y sample more p o i n t s on the d a r k a d a p t a t i o n c u r v e . A l s o t h e p a r t i c u l a r methods o f d e d u c i n g s p e c -t r a l s e n s i t i v i t y from d a r k a d a p t a t i o n c u r v e s v a r y f r o m paper t o p a p e r , as do r e t i n a l l o c a t i o n s ' s t u d i e d , c o l o r e d f i l t e r s u s e d ( b r o a d band v s . n a r r o w b a n d ) , and most i m p o r t a n t l y , as i t : t u r n s o u t , t h e l e v e l s o f p r e - a d a p t a t i o n i n v o l v e d . (The o r d e r s o f ma g n i t u d e i n comparable u n i t s : 5 min. a t 10^ -6 6 10 . mL f o r Wald and- A u e r b a c h , 5 m i n . a t l e v e l s g r e a t e r t h a n 10' mL f o r 3 i Das, 4 m i n . a t 10 mL f o r Handelbaum and "Mint z , 10 . mL. f o r 0.17 m i n . o r -2 10 mL. f o r 1.40 min. f o r Hanson and A n d e r s o n ) . That i n t e n s i t y i s a v e r y i m p o r t a n t v a r i a b l e i s i l l u s t r a t e d by c u r v e s o b t a i n e d by Dodt and E l e n i u s 0-960): w i t h s t r o n g w h i t e p r e - a d a p t a t i o n orange and b l u e t e s t l i g h t s r e -s u l t i n s e p a r a t e cone c u r v e s ; a t l e v e l s o f p r e - a d a p t a t i o n o n l y 0.6 l o g u n i t l o w e r the c u r v e s c o i n c i d e . A l l f o u r p a p e r s a g r e e t h a t r e d p r e - a d a p t a t i o n s l o w s r e c o v e r y f o r l o n g w a v e l e n g t h t e s t c o l o r s , and t h a t b l u e p r e - a d a p t a t i o n s l o w s s h o r t wave-l e n g t h r e c o v e r y . L i k e w i s e , p r e - e x p o s u r e w i t h r e d p r o d u c e s a s a v i n g s i n s e n s i t i v i t y i f d a r k a d a p t a t i o n i s done w i t h a b l u e t e s t p a t c h . Wald and Auerbach's c u r v e s a r e somewhat more complex, however, because cone c u r v e s w h i c h t a p " s p a r e d " r e c e p t o r s can show m u l t i p l e p l a t e a u s , and t h e y c o n c l u d e t h a t t h e r e i s a v i o l e t r e c e p t o r w i t h a maximum s e n s i t i v i t y a round 436 mjuu . Das has d e m o n s t r a t e d t h a t bumpy cone'curves, a r e n ' t a n e c e s s a r y c o n d i t i o n f o r u n c o v e r i n g s u c h a r e c e p t o r s - h e f i n d s . o n e . r e s p o n s i b l e f o r t h e f i r s t 30 seconds o f smooth c u r v e s . Mandelbaum and T l i n t z ' s smooth c u r v e s l e a d them t o d e s c r i b e t h r e e r e c e p t o r s e n s i t i v i t y c u r v e s h a v i n g a l m o s t i d e n t i c a l maxima. 32 D i s c r e p a n c i e s i n d a r k . a d a p t a t i o n curves are probably due on the one'hand to .methods of p l o t t i n g : a n d i n t e r p r e t a t i o n of p la teauing—Wald and Auerbach p l o t more p o i n t s than anyone e l s e - - a n d i n t e n s i t y e f f e c t s on the o t h e r - - i f weak orange p r e - adap t a t i on d i d n ' t knock but the long wave-l e n g t h r ecep to r s comple te ly they might tend to smooth out an o therwise p l a t e a u i n g shor t wavelength: da rk adap ta t i on cu rves . The q u e s t i o n remains whether i t would b e . p o s s i b l e to d e r i v e Wald, Auerbach, and Das ' s p e c t r a l s e n s i t i v i t y curves from Mandelbaum, M i n t z , Hanson, and Anderson dark adap-t a t i o n curves u s i n g the Wald, Auerbach, Das r e a s o n i n g , and v i e e v e r s a . Probably n o t , s i n c e the l a t t e r set of curves show sma l l t h r e s h o l d d i f f e r -ences due to wavelength compared to the former- set; , p o s s i b l y i n t e n s i t y u n d e r l i e s the i n c o m p a t i b i l i t y . 33 T e s t f i e l d L o c a t i o n , • S i z e , and D u r a t i o n The e f f e c t s o f t h e s e t h r e e v a r i a b l e s on d a r k a d a p t a t i o n can i n p a r t , be a c c o u n t e d f o r by the s p a t i a l d i s t r i b u t i o n o f rods and cones a c r o s s t h e r e t i n a ( s ee 'Figure 7 ) . '/Moreover, s i n c e a i l t h r e e t e n d t o i n t e r a c t w i t h one a n o t h e r , i t i s u s e f u l t o c o n s i d e r them t o g e t h e r . Sloan'C1950) found.that< f i n a l d a r k a d a p t a t i o n r o d t h r e s h o l d s f o l l o w r e c e p t o r d e n s i t y a c r o s s t h e r e t i n a ; n e i t h e r l i g h t a d a p t e d r o d n o r cone t h r e s h o l d s f o l l o w d e n s i t y as p r e c i s e l y . "More s p e c i f i c a l l y , t h e f u r t h e r away t h e t e s t f l a s h f r o m t h e f o v e a , t h e l o w e r t h e r o d t h r e s h o l d up t o about 10° ( H e c h t , H a i g , and Wald, 1936). Beyond 20° t h e r e l a t i o n r e v e r s e s - CSloan, 1950) and i n c r e a s i n g e c c e n t r i c i t y i n c r e a s e s t h e t h r e s h o l d . The t r e n d i s f o r cone f i n a l t h r e s h o l d s t o i n c r e a s e from t h e f o v e a t o t h e p e r i p h e r y , a l t h o u g h more r a p i d l y . t h a n the cone d e n s i t y d e c r e a s e s , and even beyond 60° t e m p o r a l l y where cone d e n s i t y b e g i n s t o i n c r e a s e . ' The t e m p o r a l r e t i n a i s more s e n s i t i v e g e n e r a l l y t h r o u g h o u t d a r k a d a p t a t i o n t h a n t h e n a s a l r e t i n a ( S l o a n , 1950). DeGroot, Dodge and S m i t h , (1952) f o u n d t h i s a l s o f o r s c o t o p i c b r i g h t n e s s measurements, and a l t h o u g h d i f f e r e n c e s between upper and l o w e r v s . n a s a l and t e m p o r a l q u a d r a n t s . emerged from t h i s study,, the i n t e r s q u a d r a n t d i f f e r e n c e s a r e much s m a l l e r t h a n m e r i d i n a l d i f f e r e n c e s . , Wolf and Z i g l e r 0.951) have c o n f i r m e d S l o a n and H e c h t , H a i g and Wald's r e s u l t s i n a more r e s t r i c t e d s t u d y far the f o v e a and 6° p e r i p h e r a l l y ; t h e y p o i n t out t h a t p a r a f o v e a l r o d and cone f i n a l t h r e s h o l d d i f f e r e n c e s " 34 E E CT in in <D C Q- 3 i - o ^ O — Q-<D U a: 5 6 J L J L cones rods _ J L 60 . 40 20. Nasal F i e l d 60° 80° 20° 40° Temporal F i e l d (Retinal F i e l d ) %elin*.t density ^ IrAoCie/tts for rod} ctntt Cones Jhcm Siea-n, if 5~o a^tcr 1enVo<sscAA.te. * Os/erSery 35 a r e l a r g e r t h a n f o v i a l d i f f e r e n c e s , w h i c h c o i n c i d e s w i t h r e l a t i v e d e n s i t y d i f f e r e n c e s i n t h e f o v e a and p e r i p h e r y . S i n c e t h e t e s t p a t c h i s n e v e r a one d i m e n s i o n a l p o i n t o f l i g h t , r e t i n a l l o c a t i o n e f f e c t s m i g h t be confounded w i t h s i z e e f f e c t s , But t h e . l°-2° t e s t a r e a s used a r e s m a l l compared t o t h e r e c e p t o r d e n s i t y g r a d i e n t , so f o r most p u r p o s e s s t u d i e s on t h e e f f e c t o f l o c a t i o n , i n s o f a r as r e -c e p t o r d e n s i t y i s t h e i m p o r t a n t < f a c t o r , sample e s s e n t i a l l y homogenous a r e a s . However, e x p e r i m e n t s d e a l i n g w i t h the s i z e v a r i a b l e o f t e n confound th e l o c a t i o n v a r i a b l e , so t h a t r e c e p t o r d i s t r i b u t i o n can be h e l d t o a c c o u n t f o r an a p p a r e n t s i z e e f f e c t . G e n e r a l l y , ' t h e l a r g e r t h e t e s t p a t c h t h e l o w e r t h e t h r e s h o l d , the sooner t h e p o i n t a p p e a r s , and t h e h i g h e r the r o d r a t e o f a d a p t a t i o n (Wolf and Z i g l e f , 1950* H e c h t , H a i g and Wald, 1936, C r a w f o r d , 1947) b o t h f o v e a l l y and p e r i p h e r a l l y . But l o c a t i o n e f f e c t s e n t e r i n t o two of Wolf and Z i g l e r ' s f i n d i n g s : (1) f o r any s i z e , r o d t h r e s h o l d s a r e . h i g h e r i n t h e f o v e a t h a n i n t h e p e r i p h e r y . ' I n f a c t , H e c h t , H a i g and Wald p r o p o s e that., e s -p e c i a l l y i n t h e f o v e a where d e n s i t y g r a d i e n t s a r e so s t e e p , i t i s l o c a t i o n and n o t s i z e t h a t d e t e r m i n e s t h r e s h o l d as e v i d e n c e by t h e f a c t t h a t a l " t h i c k 20° a n n u l u s has t h e same r o d t h r e s h o l d s t h r o u g h o u t d a r k a d a p t a t i o n . As a f u l l 20° c i r c l e , the most s e n s i t i v e p e r i p h e r a l a r e a s a r e d e t e r m i n i n g t h e t h r e s h o l d . Wolf and Z i g l e r ' s c u r v e s show i n a d d i t i o n , , t h a t c e n t r a l cone c u r v e s a r e n ' t f a c i l i t a t e d beyond a 5° s i z e — t h e r e s u l t no doubt of 5° 36 having covered a l l the most s e n s i t i v e cone l o c a t i o n s a l r e a d y . Other s t u d i e s (LeGrand, p . 251) have attempted to es t imate the summating power of the r e t i n a as i t r e l a t e s to the i n t e r a c t i o n of t e s t p a t c h s i z e and r e t i n a l l o c a t i o n . I f L i s the t h r e sho ld i n t e n s i t y , A i s the area of the t e s t f l a s h , and C i s a constant dependent on time i n the dark , then LA = C, where ~x i n d i c a t e s the amount of summation,-, i f x = 1 then summation , i s complete. The. d e t a i l s are compl i ca t ed , but the t rend i s fo r x to be s m a l l i n the fovea and l a r g e r i n the p e r i p h e r y . Wi th i n c r e a s i n g e c c e n t r i c i t y summation improves a l though i t improves f a s t e r fo r s m a l l t e s t patches than fo r l a r g e ones. Insofa r as l o c a t i o n e f f e c t s d o n 1 t account for s i z e e f f e c t s i n experiment l i k e the Wolf and Z i g l e r paper , the v a r i a t i o n in.summation across the r e t i n a p robab ly can . As fo r t e s t f i e l d d u r a t i o n , the longer the f l a s h , the lower the t h r e s h o l d (Wolf and Z i g l e r , .1951) , and the fundamental cause i s a s c r i b e d to the g rea te r number of recep tors e x c i t e d by the i nc r ea se i n energy from a longer f l a s h ( i . e . temporal summation). However, rods are f a c i l i -t a ted more ' than cones,and they make the b igges t gains a t the fovea , so d e n s i t y or d e n s i t y grad ien t d i f f e r e n c e s , or p h o t o c h e m i c a l ^ a n d c n e u f a l • d i f f e r -ences between rods and cones as w e l l as between c e n t r a l and p e r i p h e r a l rods must be o p e r a t i n g he re . 37 E. P u p i l D i a m e t e r No s y s t e m a t i c i n v e s t i g a t i o n s of t h e e f f e c t of p u p i l s i z e on d a r k a d a p t a t i o n c u r v e s have been c a r r i e d out i n s p i t e o f t h e t h e o r e t i c a l and p r a c t i c a l i m p o r t a n c e of t h i s p r e — r e t i n a l f a c t o r . There i s . r e a s o n a b l e agreement t h a t f o r s u b j e c t s w i t h , n o r m a l . p u p i l l a r y r e f l e x e s , p u p i l s i z e i s n o t an i m p o r t a n t v a r i a b l e ( f o r i n s t a n c e , Mandelbaum, 1 9 4 1 ) , p r e s u m a b l y because i t s e f f e c t s a r e s m a l l e r t h a n t h e s u b j e c t ' s 0.3 l o g u n i t day t o day n o n - c l i n i c a l v a r i a b i l i t y . However, any c l i n i c a l s t u d y where non-normal p u p i l l a r y r e f l e x e s may be i n v o l v e d must a l l o w f o r p u p i l d i f f e r e n c e s between a n o r m a l c o n t r o l group and t h e c l i n i c a l g r oup, as w e l l as w i t h i n t h e c l i n i c a l group i t s e l f . J a y l e , Ourgaud, A u b e r t , and R e b o u l (1961) g i v e an example o f a one l o g u n i t r i s e i n t h r e s h o l d f o r a n ormal s u b j e c t , and an 0.5 l o g u n i t r i s e f o r a glaucomatous s u b j e c t , b o t h c o r r e s p o n d i n g t o a 3-4 mm. r e d u c t i o n i n p u p i l s i z e . The b r i g h t n e s s o f the r e t i n a l images d u r i n g p r e - e x p o s u r e and d a r k a d a p t a t i o n u l t i m a t e l y depends.on p u p i l s i z e . Mandelbaum (1941) i s o f t h e o p i n i o n t h a t p u p i l l a r y changes f o l l o w i n g t h e t e r m i n a t i o n o f p r e - e x p o s u r e o p e r a t e a l o n g w i t h r e t i n a l changes, t o a c c o u n t f o r t h e l o w e r i n g t h r e s h o l d s d u r i n g o n l y t h e cone phase of d a r k . a d a p t a t i o n : , ( i i o t t c e t h e i m p l i c a t i o n t h a t w i t h a f i x e d a r t i f i c i a l p n p i l t h e shape o f t h e cone c u r v e w i l l be d i f f e r e n t t h a n w i t h a n a t u r a l p u p i l ) , P h i l l i p s (1939)., who d i d e x t e n s i v e work on t h e p r o b l e m found,.however, t h a t a s m a l l . p u p i l d u r i n g p r e - e x p o s u r e c o u l d f a c i l i t a t e even t h e r o d p o r t i o n of d a r k a d a p t a t i o n , a l t h o u g h t h a t s e c t i o n 38 i s a l s o i n f l u e n c e d by p u p i l s i z e i n t h e d a r k . A l s o , among no r m a l young s u b j e c t s , p u p i l s i z e ± 1 t h e l i g h t c o r r e l a t e s p o s i t i v e l y w i t h p u p i l s i z e i n t h e dark.' One common means f o r c o n t r o l l i n g p u p i l s i z e i s t h e a r t i f i c i a l p u p i l , w h i c h p l a c e s an o p e n i n g i n f r o n t o f t h e eye s m a l l e r t h a n any no r m a l p u p i l o p e n i n g e n c o u n t e r e d d u r i n g t h e e x p e r i m e n t ; i t i s much too demanding a t e c h n i q u e f o r c l i n i c a l s t u d i e s . M i o t i c s and m y d r i a t i c s w h i c h e i t h e r c o n s t r i c t o r d i a l a t e t h e p u p i l a r e more e x t e n s i v e l y u s e d , a l t h o u g h t h e i r drawbacks a r e s e r i o u s ( S l o a n , 1940; Z b a r s k i i , 1958; S t e w a r t , M a d e l l and D y e r , 1968); t h e y may change r e t i n a l s e n s i t i v i t y ; t h e y don't e f f e c t e v e r y p u p i l e q u a l l y ; mio-t i c s may a f f e c t p u p i l s i z e f o r up t o t h r e e weeks i n n o r m a l young s u b j e c t s ; and, most s i g n i f i c a n t l y , ,they may a f f e c t d a r k a d a p t a t i o n d i f f e r e n t l y i n a c l i n i c a l p o p u l a t i o n t h a n i n a normal one even when p u p i l , s i z e i s a c o n s t a n t f a c t o r , o r t h e y may a f f e c t v a r i o u s p a r t s o f t h e c u r v e d i f f e r e n t l y among no r m a l s u b j e c t s ( Z b a r s k i i , 1958; J a y l e , Ourgaud, A u b e r t , R e b o u l , 1961; L i n d s t r o m , T r e d i c i , M a r t i n , 1968). The p o s s i b i l i t y t h a t d r u g s may a l t e r t h e dynamic changes o f p u p i l s i z e between i n d i v i d u a l s , as the eye i s s u b j e c t e d t o changes i n i l l u m i n a t i o n s h o u l d n ' t be o v e r l o o k e d . When and how s h o u l d d a r k a d a p t a t i o n t h r e s h o l d s be c o r r e c t e d f o r p u p i l s i z e ? A g a i n , no s y s t e m a t i c s t u d i e s g u i d e t h e answer; t h e r e a r e a l m o s t as many s u g g e s t i o n s as t h e r e a r e p a p e r s on t h e t o p i c : 39 (1) S l o a n (1950) c o r r e c t s f o r t h e d e c r e a s e i n e f f e c t i v e p u p i l a r e a f o r p e r i p h e r a l t e s t a r e a s among no r m a l s u b j e c t s , b u t Zuege and D r a n c e , (1967) d o n ' t . (2) J a y l e , Ourgaud, A u b e r t and R e b o u l (1961) m o d i f y t h e r u l e t h a t n o r m a l p u p i l s don't r e q u i r e c o r r e c t i o n s by recommending t h a t w i t h p u p i l s b elow 3.5 mm,(mesopic i l l u m i n a t i o n ) some c o r r e c t i o n be made. S l o a n (1940) u s e s 5 m m , i l l u m i n a t i o n ( u n s p e c i f i e d ) as a c u t - o f f . (3) H a i g (1939) s u g g e s t s t h a t an a r t i f i c i a l p u p i l i s n e c e s s a r y o n l y a t l ow p r e - e x p o s u r e s . (4) C o r r e c t i o n s a r e u s u a l l y based on p u p i l a r e a and a r e c a l c u l a t e d so as t o b r i n g a l l t h r e s h o l d s i n l i n e w i t h an a r b i t r a r y s t a n d a r d p u p i l a r e a , b u t c o n t r o v e r s y abounds o v e r whether t h e S t i l e s - C r a w f o r d e f f e c t i s i m p o r t a n t a t t h e s c o t o p i c l e v e l , and so whether cone t h r e s h o l d s s h o u l d be a l t e r e d a c c o r d i n g t o an " e f f e c t i v e a r e a " w h i c h i s d i f f e r e n t f r o m t h e s i m p l e geo-m e t r i c a l a r e a : i t has been s a i d t o p e r s i s t as under p h o t o p i c c o n d i t i o n s , t o o p e r a t e n o t a t a l l , o r t o be r e v e r s e d ( J a y l e , Ourgaud, B a i s i n g e r , Holmes, 1959). S l o a n (1950) i s s a t i s f i e d t h a t i t d o e s n ' t e x i s t , Zuege and Drance C1967), S p a e t h (1934) and Wa i t Derby and K i r k (1925) don't a l l o w f o r i t , and Mandelbaum ( 1 9 4 1 ) , whose c o r r e c t i o n c u r v e s a r e the o n l y oness b a s e d on e m p i r i c a l e v i d e n c e , i m p l i e s t h a t i t must be a l l o w e d f o r . The s i n g l e most s e r i o u s f a i l i n g i n e v e r y c o r r e c t i o n method-/except one ( H e c h t ) , i s t h e a s s u m p t i o n t h a t a s i n g l e , p u p i l measurement t a k e n a t one u n s p e c i f i e d time i n the d a r k i s t h e a p p r o p r i a t e one t o c o r r e c t f o r . 40 No r e c o g n i t i o n i s made tha t the p u p i l changes s i z e d u r i n g dark a d a p t a t i o n , and no attempt has been made to determine whether the changes would s i g -n i f i c a n t l y a l t e r t h r e sho ld c o r r e c t i o n s ' b e y o n d the ones based on a s i n g l e p u p i l s i z e . J a y l e , Ourgaud, Aube r t , and R e b o u l ' s (1961) curves suggest tha t no constant a d d i t i v e or m u l t i p l i c a t i v e c o r r e c t i o n can t ransform a curve fo r a s m a l l p u p i l measured once i n t o One f o r a l a r g e r p u p i l . A l F. Age and Dark Adaptation Table IV summarizes the main findings of several important re-searches in ,this area. Although methods differ widely, the general con-sensus i s that both rod and cone thresholds increase with advancing age. In fact, since thresholds are highly correlated with each other for any individual, and thresholds are correlated with age for any time in, the dark, Domey and McFarland (196,1) were able to give accurate predictions of f i n a l thresholds for individuals on the basis of their early thresholds and age. Also, there is agreement that the most dramatic deterioration in dark adaptation takes place after 40. But i f rod and cone dark adapta-tion rates are influenced by age, i t s action remains unconfirmed. Special attention is due to the Verriest and Haznedaroglu paper because i t indicates that there is an early developmental effect on rod and cone thresholds,1 as well as on cone rate; McFarland and Fisher's (1955) work is suggestive in this direction for rod rate. There i s reason to believe that the deleterious effects of age on dark adaptation are not homogenous for older populations; the s i g n i f i -cance of the age effect is accompanied by the occurrence of a greater number of individuals with very poor adaptation alongside contemporaries • with more moderate losses. Birren, Bick and Fox (1948) are the only ones who bothered to investigate gross sampling bias as an underlying cause of this effect and concluded that i t was not a significant factor i n their 42 own work. However, M c F a r l a n d , Domey, Warren and Ward ( 1 9 6 0 ) , who seem t o have amassed a v e r y u n b i a s e d p o p u l a t i o n o f 240, found t h a t t h r e s h o l d v a r i a b i l i t y between s u b j e c t s d i d not i n c r e a s e w i t h age, so perhaps t h e i s s u e i s n o t a c l o s e d one. S i n c e t h e u l t i m a t e mechanisms o f a g i n g on d a r k a d a p t a t i o n must be t i e d t o t h e s t a t i s t i c a l d i s t r i b u t i o n o f t h r e s h o l d s , i t i s of some i n t e r e s t t o r e s o l v e t h e s e p r o b l e m s . R o b e r t s o n and Y u d k i n (1944) and S l o a n (1947, as c i t e d i n " N i g h t V i s i o n " , J a y l e , Ourgaud, B a i s i n g e r , Holmes, 1959) f a v o r . t h e d e c r e a s e i n p u p i l s i z e as the u l t i m a t e cause o f d a r k a d a p t a t i o n . l o s s w i t h age; P h i l l i p s ( 1 9 3 9 ) , B i r r e n and Shock (1950) and B i r r e n , B i c k and Fox (1948) don't a g r e e . Hecht and Mandelbaum (1939) have e x c l u d e d t h e y e l l o w i n g o f the l e n s as the f a c t o r and L u r i a ( I 9 6 0 ) e l i m i n a t e d s u b j e c t , judgment.. More p o s i t i v e . s u g g e s t i o n s f o r mechanisms a r e e i t h e r p r e - r e t i n a l ( i n c r e a s e d o p a c i t y o f t h e media, r e f r a c t i v e changes) o r r e t i n a l ( s t r u c t u r a l changes'' , i n s u f f i c i e n t n o u r i s h m e n t , d e f i c i e n t m e t a b o l i s m ) ; t h e q u a n t i t y and q u a l i t y o f a s u b j e c t ' s d i e t has a l s o been c o n s i d e r e d ( W osika, 1 9 4 3 ) , b u t l i k e a l l t h e o t h e r c auses m e n t i o n e d , i t r e m a i n s a p u r e l y s p e c u l a t i v e one. 43 G. Glaucoma: A G e n e r a l C h a r a c t e r i z a t i o n D e f i n i t i o n V a r i o u s a t t e m p t s have been made by v a r i o u s a u t h o r i t i e s t o d e f i n e the . ' d i s e a s e . Law (1957), says "...glaucoma i s a name g i v e n t o a group o f c o n d i t i o n s o f v a r y i n g p a t h o l o g y . . . a l l o f w h i c h have one f a c t o r i n common—that o f r a i s e d o r u n s t a b l e o c u l a r t e n s i o n . " B e c k e r and S h a f f e r (p.59) go f u r t h e r and i m p l i c a t e r a i s e d p r e s s u r e as a mechanism: " G l a u -coma may be d e f i n e d f o r t h e i n d i v i d u a l eye as t h e i n t r a o c u l a r p r e s s u r e w h i c h p roduces damage t o t h e o p t i c n e r v e . " Prom t h i s l a s t d e f i n i t i o n f o l l o w f o u r o t h e r p o i n t s t h a t a r e f a i r l y r e p r e s e n t a t i v e of t h e c l i n i c i a n ' s b i a s : (1) n o t a l l o p t i c n e r v e s a r e i n t o l e r a n t o f h i g h p r e s s u r e s ; (2) a d e f i n i t e d i a g n o s i s o f glaucoma can be made o n l y when i n c r e a s e d i n t r a o c u l a r (IOP) has r e s u l t e d i n o p t i c n e r v e damage ( i . e . , f i e l d c h a n g e s ) ; (3) a s e a r c h f o r mechanisms i s e q u i v a l e n t t o a s e a r c h f o r t h e c a u s e s o f r a i s e d IOP's; (4) the c l i n i c i a n ' s t a s k i s t o p r e d i c t , , u s i n g r e l i a b l e c r i t e r i a , w h i c h eyes w i l l undergo i n e v i t a b l e o p t i c n e r v e damage. That a l l t h i s i s t o o s i m p l i f i e d a p i c t u r e o f t h e s i t u a t i o n w i l l emerge i n what f o l l o w s . C l a s s i f i c a t i o n A l l t h e glaucomas come under one of t h r e e c a t e g o r i e s : p r i m a r y * c o n g e n i t a l , and s e c o n d a r y ( t o o t h e r o c u l a r d i s e a s e s , t h a t i s ) . . B o t h t h e . 44 s e c o n d a r y and p r i m a r y a r e s p l i t i n t o open and c l o s e d a n g l e ; t h e " a n g l e " i n q u e s t i o n i s t h e one i n t h e a n t e r i o r chamber between t h e i r i s and t h e c o r n e a where the aqueous humor w h i c h i s u l t i m a t e l y r e s p o n s i b l e f o r t h e p r e s s u r e w i t h i n the e y e b a l l d r a i n s from t h e p o s t e r i o r and a n t e r i o r cham-b e r s (see F i g u r e s 8 and 9). Closed, a n g l e glaucoma can be c h r o n i c or a c u t e . Open a n g l e glaucoma, which, i s t h e most i n t e r e s t i n g f o r m , i s u s u a l l y s p l i t i n t o two t y p e s — o n e showing a d e c r e a s e d f a c i l i t y o f o u t f l o w o f aqueous, and one h a v i n g a n o r m a l o u t f l o w but an i n c r e a s e ' i n aqueous p r o d u c t i o n o r an i n c r e a s e i n t h e b l o o d p r e s s u r e i n t h e v e s s e l s s u r r o u n d i n g the e y e b a l l . N o t i c e t h a t t h e whole c l a s s i f i c a t i o n s y s t e m i s b u i l t around mech-anisms of r i s e i n I O P — a r e f l e c t i o n of t h e p r e v a i l i n g f a i t h i n t h e p r i m a c y o f t h a t mechanism. But t h e anomalous "low t e n s i o n open a n g l e glaucoma" p u t s i n r e l i e f t h e i n a d e q u a c y o f t h e c l a s s i f i c a t i o n a r i s i n g f r o m t h e r e -s t r i c t e d knowledge we have about t h e development o f t h e d i s e a s e . I t s o c c u r r e n c e must sometimes' be. e x p l a i n e d b y . " o t h e r causes of damage t o t h e r e t i n a and o p t i c n e r v e ? " ( B e c k e r and S c h a f f e r ) . The c o n c e p t o f a weakened o p t i c n e r v e r e s u l t i n g f r o m r e d u c e d b l o o d p r e s s u r e o r poor n u t r i t i o n o f the n e r v e e n t e r s h e r e . The s u g g e s t i o n t h u s a r i s e s t h a t r a i s e d IOP's i n glaucoma o f t e n accompany i m p a i r e d n o u r i s h m e n t o f t h e n e r v e but a r e n o t the d i r e c t cause o f i t s d e s t r u c t i o n , e s p e c i a l l y c o n s i d e r i n g t h a t a h i g h p r e s s u r e may be t o l e r a t e d w e l l by one p e r s o n ' s eye and n o t toy a n o t h e r ' s . 45 3r&c'/fAj£ route, in tAe YurrnuU eye from flecker r ?A* //eh , I Hi, f • IS 46 T^tirujrtt'on of fJorma,t otrtttroutes M oyen &tta( Closed bnjU j(*«x*m*s. from letkeirt SAA/ft/• tf-ll-& 47 C l i n i c a l C h a r a c t e r i s t i c s 1. R a i s e d I n t r a o c u l a r P r e s s u r e The i n t r a o c u l a r p r e s s u r e i n mm.of me r c u r y i s g i v e n as P Q = F/C+P , where P Q i s the. i n t r a o c u l a r p r e s s u r e , F i s t h e r a t e o f aqueous s e c r e t i o n ( m l / m i n . ) , C i s t h e o u t f l o w f a c i l i t y , and P ^ i s t h e e p i s c l e r a l venous p r e s s u r e . . The measurement o f P Q depends on e i t h e r t h e a p p l i c a t i o n o f a s t a n d a r d f o r c e t o the e y e b a l l and an o b s e r v a t i o n o f t h e amount o f i n d e n -t a t i o n i t c a u s e s , o r on t h e o b s e r v a t i o n o f t h e f o r c e r e q u i r e d t o produce a s t a n d a r d i n d e n t a t i o n ( B e c k e r and S c h a f f e r , C h a p t e r 5 ) . The mean IOP i s 15.4 mm.with a s t a n d a r d d e v i a t i o n o f 2.5; the IOP tend s t o i n c r e a s e w i t h age. 2. F i e l d Changes Because t h e axons o f g a n g l i o n c e l l s a r e a c r o s s t h e r e t i n a as t h e y t r a v e l t o t h e b l i n d s p o t ( O p t i c d i s c ) , damage t o an axon i n t h e a r e a o f the d i s c p r o d u c e s d e f e c t s a t p l a c e s a l o n g t h e r e t i n a communicating v i a t h e axon. The e f f e c t s o f p r o l o n g e d p r e s s u r e on t h e d i s c ( B e c k e r and S c h a f f e r ) r e s u l t i n (1) enlargement o f t h e b l i n d s p o t , and (2) n e r v e f i b r e b u n d l e d e f e c t s i n w h i c h a scotoma f o l l o w s t h e a r c i n g c o u r s e o f an axon from the b l i n d s p o t t o t h e p e r i p h e r y on t h e o t h e r s i d e , o f t e n f o r m i n g a " n a s a l s t e p " a t t h e h o r i z o n t a l r e p he. C l a s s i c a l l y , f o v e a l v i s i o n i s t h e l a s t t o go as t h e d i s e a s e p r o g r e s s e s ; t h e r e s i d u a l f i e l d i n advanced glaucoma i s l o c a t e d i n a t e m p o r a l c r e s c e n t . 48 3. D i s c Changes The r e t i n a l and o p t i c n e r v e b l o o d s u p p l i e s a r e s e p a r a t e : the d i s c i s the s i t e o f e n t r a n c e of the r e t i n a l v e s s e l s , and t h e a r e a b e h i n d t h e d i s c i s t h e a r e a where t h e o p t i c n e r v e r e c e i v e s i t s b l o o d s u p p l y . ; I n glaucoma, a t r o p h y of n e r v e s and g l i a a t t h e d i s c c auses t h e membrane c o v e r i n g t h e o p e n i n g t o cup back and t h e r e t i n a l b l o o d v e s s e l s t o be d i s -p l a c e d . I t ' s g e n e r a l l y thought t h a t h i g h IOP's a c t n o t d i r e c t l y on t h e axons e x i s t i n g a t t h e d i s c , b u t r a t h e r on t h e i r b l o o d s u p p l y a t t h e b a s e o f t h e d i s c ; B e c k e r and S c h a f f e r s u g g e s t t h a t t h e r e t i n a l v e s s e l s a r e l e s s s u b j e c t t o p r e s s u r e b e c a u s e , u n l i k e t h e v e s s e l s n o u r i s h i n g t h e o p t i c n e r v e , t h e y have no e x t r a - o c u l a r b r a n c h e s and b l o o d cannot be s h u n t e d o u t o f them. There i s l i t t l e doubt t h a t i t i s t h e i n t e r a c t i o n o f i n c r e a s e d IOP and r e t i n a l o r n e r v e head v a s c u l a r i n s u f f i c i e n c y w h i c h d e t e r m i n e s whether o r n o t "glaucoma w i l l d e v e l o p , as i t i s p o s s i b l e f o r . a cupped d i s c and a glaucomatous f i e l d t o appear w i t h no e l e v a t i o n i n IOP. Mechanisms i n p r i m a r y glaucoma The p r e c e d i n g d i s c u s s i o n c o u l d n ' t a v o i d a c o n s i d e r a t i o n o f mechan-i s m s , b u t t h i s s e c t i o n w i l l s e t down t h e i r ( n o t n e c e s s a r i l y e x c l u s i v e ) m ajor c a t e g o r i e s . 1. I n c r e a s e d i n t r a o c u l a r p r e s s u r e The mode o f a c t i o n h e r e i s f o r t h e i n c r e a s e d t e n s i o n t o r e s u l t i n an i m p a i r m e n t o f t h e c i r c u l a t i o n t o t h e o p t i c n e r v e , and per h a p s t o t h e 49 r e t i n a i t s e l f . R e s e a r c h e r s f a v o r i n g more comprehensive mechanisms, must n e v e r t h e l e s s , a c c o u n t f o r the r a i s e d IOP i n , g l a u c o m a . V a r i o u s a c c o u n t s have been g i v e n f o r the p r e s s u r e r i s e i t s e l f : a d e c r e a s e i n o u t f l o w f a c i l i t y , an i n c r e a s e i n P , and h y p e r s e c r e t i o n o f i n t r a o c u l a r f l u i d s . There i s much c o n t r o v e r s y o v e r whether a d e c r e a s e i n o u t f l o w f a c i l i t y i s a cause o f an e f f e c t o f t h e r a i s e d IOP (Levene, 1969, 1 9 7 0 ) — t h a t i s , p o s s i b l y t h e s i t e o f d r a i n a g e i s p r e s s u r e - s e n s i t i v e and s u f f e r s permanent damage f r o m c h r o n i c o r i n t e r m i t t e n t r i s e s i n IOP. 2. D e f i c i e n c y o f Home o s t a s i s P o s s i b l y n e u r a l ( a u t o n o m i c , or a c c o r d i n g t o Cavaka, 1956, even, d i e n c e p h a l i c i n o r i g i n ) o r hormonal f e e d b a c k systems (Lerman) breakdown i n . g l a u c o m a so t h a t an i n c r e a s e i n t h e r a t e o f s e c r e t i o n i s n o t compensa-t e d f o r by an enhanced d r a i n a g e , o r i m p a i r e d d r a i n a g e i s n o t remedied by h y p o s e c r e t i o n as i t would be i n a no r m a l eye. F o r i n s t a n c e , i n - t h e n o r m a l eye ( H a r r i s o n , 1 9 6 2 ) , a r i s e i n IOP caused by an i n c r e a s e i n i n t r a c l e r a l venous .pressure ( t h e v e i n s where aqueous d r a i n s ) would be met by a d e c r e a s e i n the u v e a l b l o o d f l o w , and so i n t h e r a t e o f s e c r e t i o n . 3. V a s c u l a r T h e o r i e s These appear t o s t r i v e toward a t r u l y c o m prehensive e t i o l o g y ; even a n g l e c l o s u r e glaucoma has an e x p l a n a t i o n h e r e (Law). S t r e s s i s p l a c e d on t h e u n b a l a n c i n g o f v a s c u l a r and i n t r a o c u l a r t e n s i o n s , ( L e v e n e , 1970, ; Feldman, Sweeney and Dranoe,1969; D r a n c e , 1968),so t h a t l o w t e n s i o n glaucoma l o s e s i t s m y s t e r i o u s o r i g i n s . R a i s e d IOP i s n ' t a p r i m a r y cause even when 50 i m p a i r e d o u t f l o w i s i m p l i c a t e d , s i n c e t h a t impairment can be seen as a s p e c i f i c e f f e c t o f v a s c u l a r i n s u f f i c i e n c y w h i c h may e x i s t a t t h e r e t i n a l , c h r o r i d a l , o r o p t i c n e r v e l e v e l s , and perhaps t h e i n t r e s c l e r a l as w e l l ( Levene, 1969, 1970; S h l a i f i g j ^ 1967, Law). ' . > - -51 ; H. Glaucoma and Dark A d a p t a t i o n A l t h o u g h the p r e s e n t s t u d y d e a l s w i t h eyes t h a t a r e n o t s t r i c t l y g l a u c o m a t o u s , t h e glaucoma l i t e r a t u r e i s t h e o b v i o u s p l a c e t o t u r n f o r a h i n t o f what changes t o l o o k f o r i n t h e h y p e r t e n s i v e eye. T a b i e V i s an at t e m p t t o summarize some of t h e i m p o r t a n t s t u d i e s . i n glaucoma and d a r k a d a p t a t i o n . Even a c a s u a l i n s p e c t i o n o f t h e T a b l e r e v e a l s s e r i o u s o b s t a c l e s t o d r a w i n g c o n c l u s i o n s . S l o a n , i n 1939, r e v i e w e d t h e d a r k a d a p t a t i o n l i t e r a t u r e as i t p e r t a i n e d t o c l i n i c a l t e s t i n g and p o i n t e d out t h a t s t a n d a r d i z a t i o n o f t h e t e c h n i q u e s and c l i n i c a l c a t e g o r i z a t i o n was. r e g r e t -f u l l y m i s s i n g . T h i s c r i t i c i s m i s r e a s o n a b l e even f o r t h e post - 1 9 3 9 r e -s e a r c h e s . I n s p i t e of t h e s e d i f f i c u l t i e s , ' t h e o v e r a l l c h a r a c t e r i z a t i o n o f the r e s u l t s a c r o s s e x p e r i m e n t s i s f o r t h e r e t o be an " e f f e c t " ( i . e . some d i f f e r e n c e between n o r m a l eyes and eyes showing v a r i o u s and s u n d r y c l i n i -c a l s i g n s t y p i c a l o f glaucoma). C l i n i c a l and d a r k a d a p t a t i o n v a r i a b l e s a r e sometimes r e p o r t e d as a s s o c i a t e d as w e l l ( c o r r e l a t e d i s p r o b a b l y t o o s t r o n g a term because a l t h o u g h i t has been u s e d , u s u a l l y no s t a t i s t i c a l e v i d e n c e accompanies i t s u s e ) . I n " R e s u l t s and A n a l y s i s " i t becomes c l e a r t h a t t h e p r e s e n t s t u d y t e s t s y e t a n o t h e r c l i n i c a l group t h a t o v e r l a p s w i t h some o f t h e groups d e s c r i b e d i n T a b l e V. The dark' a d a p t a t i o n c u r v e s a r e o b t a i n e d w i t h 52 re fe rence to a p r e v i o u s l y ignored parameter ( i . e . . , c o l o r ) i n a r e t i n a l area probably never examined before ( i . e . , , c e n t r a l ) s ince i t i s c l a s s i -c a l l y the l a s t to succumb to the d i s e a s e . In a way, to o r i e n t an e x p e r i -ment i n t h i s way i s u n j u s t i f i e d when a l a r g e body of un-coord ina ted i n f o r m a t i o n a l r eady e x i s t s . However, i n s o f a r as the r e s u l t s are compat i -b l e w i t h o t h e r s ' r e s u l t s they w i l l serve to make the " e f f e c t " more n o t e -worthy because i t w l l have been obta ined w i t h d i f f e r e n t t echn iques . 53 I . Dark A d a p t a t i o n i n t h e C o l o r Anomalous S t u d i e s have been done from t i m e t o t i m e i n an e f f o r t t o f i n d i f s u b j e c t s w i t h c o l o r d e f e c t s show dark a d a p t a t i o n d i f f e r e n c e s compared t o c o l o r - n o r m a l s u b j e c t s . The i m p o r t a n c e o f t h i s s e e m i n g l y p e r i p h e r a l i s s u e w i l l emerge l a t e r . I t i s s u f f i c i e n t h e r e t o p o i n t out t h a t t h e c l i n i c a l p o p u l a t i o n f o r t h e p r e s e n t d a r k a d a p t a t i o n e x p e r i m e n t had been t e s t e d f o r c o l o r v i s i o n d e f e c t s . ( L a k o w s k i , B r y e t t e and Drance, 1972) and c l a s s i f i e d a c c o r d i n g l y j u s t b e f o r e t h e i r d a r k a d a p t a t i o n c u r v e s were o b t a i n e d . H i s t o r i c a l l y ( c i t e d b y C h a p a n i s , 1946, Fox, 1 9 6 0 ) , e a r l y w o r k e r s s u g g e s t e d t h a t p r o t o n s m i g h t show f a s t e r , l o w e r c u r v e s t h a n d e u t a n s , no doubt b e c a u s e t h e f o r m e r were known t o have a l u m i n o s i t y c u r v e s h i f t e d toward t h e l o n g w a v e l e n g t h s where r o d s a r e f a v o r e d . T h e r e have been two r e p o r t s c l a i m i n g t h a t no d i f f e r e n c e s e x i s t between n o r m a l s and c o l o r de-f e c t i v e s : A b e l s d o r f f e t a l . (as c i t e d by Fox) used g r e e n , w h i t e and orange l i g h t t o t e s t b o t h d i c h r o m a t s and anomalous d i c h r o m a t s ; Feldman (1941) do e s n ' t s p e c i f y h i s s u b j e c t s o r c o n d i t i o n s o f t e s t i n g . B o t h Fox (1960) and Chapanis (1946) t o o k some c a r e i n u s i n g a t e s t f l a s h w i t h a l a r g e component s i t u a t e d i n . t h e w a v e l e n g t h a r e a t h e c o l o r d e f e c t i v e was l e s s s e n s i t i v e t o t h a n a c o l o r n o r m a l . They b o t h o b s e r v e d an e x t r a p o i n t o f i n f l e c t i o n i n t h e cone p o r t i o n f o r . d e f e c t i v e s , C hapanis i n p r o t a n s w i t h a r e d t e s t f l a s h , Fox i n d e u t a n s , deutananomal^u^, and b l u e - d e v i a n t s ( f o r t h e b l u e - g r e e n e q u a t i o n ) w i t h a t e s t f l a s h dominated 54 by s h o r t w a v e l e n g t h s . The e f f e c t s i n b o t h s t u d i e s can be h a n d l e d by C h a p a n i s ' s u g g e s t i o n t h a t r o d s a r e s e n s i t i v e t o t h e t r o u b l e s o m e w a v e l e n g t h s , a l t h o u g h l e s s s e n s i t i v e t h a n t h e a p p r o p r i a t e cones i n t h e c o l o r - n o r m a l s u b j e c t , so t h e y a l l o w t h e "cone c u r v e " t o c a t c h up some b e f o r e r o d - v i s i o n p r o p e r b e g i n s i n t h e c o l o r anomalous. More r e c e n t l y , DuCroz and R u s h t o n (1966) m a i n t a i n t h a t t h e y c a n ' t c o n f i r m A u e r b a c h and Wald's (1955) o b s e r v a t i o n on deutans and p r o t o n s . The l a t t e r f o und t h a t w i t h r e d o r b l u e p r e - a d a p t a t i o n and a v i o l e t t e s t p a t c h , d eutans and p r o t o n s had s i g n i f i c a n t l y d i f f e r e n t c u r v e s f r o m c o l o r - n o r m a l s , n o t o n l y r e g a r d i n g shape, but a l s o c o l o r r e p o r t s a t v a r i o u s t i m e s d u r i n g d a r k . a d a p t a t i o n . DuCroz and R u s h t o n u s i n g w h i t e o r orange p r e - a d a p t a t i o n and a b l u e t e s t c o u l d f i n d no a b n o r m a l i t i e s i n deutans o r p r o t o n s , but-found s i m p l e r t h a n n o r m a l c u r v e s w i t h r e d p r e - a d a p t a t i o n and t e s t . How-e v e r , s i n c e . D u C r o z and Rushton's methods s u p p o s e d l y i s o l a t e d a s i n g l e ( r e d , g r e e n , o r b l u e ) w i t h i n one d a r k a i a p t a t i o n c u r v e and A u e r b a c h and Wald's was c l a i m e d t o d i s p l a y s e v e r a l cone p r o c e s s e s ( a t l e a s t ) s u c c e s s i v e l y w i t h i n one c u r v e , t h e i n c o m p a t i b i l i t y o f r e s u l t s i s n o t s u r p r i s i n g . 55 J-. Mechanisms o f Dark A d a p t a t i o n The y e a r s p r e c e d i n g 1940 were dominated by p h o t o c h e m i c a l t h e o r i e s t h a t o r i g i n a t e d w i t h Hecht ( H e c h t , 1938, H e c h t , 1937; H e c h t , H a i g and Chase, 1937; H e c h t , 1936, Hecht and Mandelbaum, 1938) and emphasized a d i r e c t r e l a t i o n between r h o d o p s i n c o n c e n t r a t i o n and r e t i n a l ( s c o t o p i c ) s e n s i t i v i t y . The background r e a s o n i n g was t h a t t h e f i r s t e v e n t i s t h e a b s o r p t i o n of one p h o t o n by one r e t i n a l r o d , so t h e v a r i a b l e c o n t r o l l i n g the t h r e s h o l d must be t h e p r o b a b i l i t y o f t h e a b s o r p t i o n o f l i g h t q u a n t a by a photopigment (LeGrand, C h a p t e r 2 0 ) . Some d i s c u s s i o n c e n t e r e d around whether t h e p h o t o c h e m i c a l e v e n t s c o u l d b e s t be r e p r e s e n t e d by a s i n g l e o r m u l t i - s t a g e p r o c e s s ( i . e . . , as ( r h o d o p s i n ) g U&hX, P + A o r as ( r h o d o p s i n ) ^a£k ^ p + A \ (Graham, - d a r k * l i g h t ' V ^ -\ C < C h a p t e r 8 ) , b u t i n any c a s e t h e t h r e s h o l d was seen as b e i n g i n v e r s e l y p r o -p o r t i o n a l t o the r h o d o p s i n c o n c e n t r a t i o n , i n d e p e n d e n t o f t h e number o f s t a g e s . E x p e r i m e n t s a t t e m p t i n g t o p r o v e t h a t d a r k a d a p t a t i o n t h r e s h o l d s a r e i n d e p e n d e n t o f n e u r a l e v e n t s e x c e p t f o r t h e e x c i t a t i o n o f t h e n e u r o n by t h e breakdown p r o d u c t s o f S i n v o l v e d v a r y i n g p r e - a d a p t a t i o n i n t e n s i t y ( H e c h t , H a i g and Chase, 1937; W i n s o r and C l a r k , 1936) and f a v o r e d t h e m u l t i s t a g e p r o c e s s . Wald and C l a r k (1937) d e v e l o p e d t h e t h e o r y by f i l l i n g i n : P = r e t i n e n e , A = a p r o t e i n , C = v i t a m i n A + p r o t e i n , and by a c c o u n t i n g f o r t h e 56 e a r l y r a p i d r o d r e c o v e r y w i t h t h e r e t i n e n e b r a n c h o f t h e e q u a t i o n and t h e l a t e r s l o w r a t e o f r e c o v e r y w i t h t h e v i t a m i n A b r a n c h . Jghn (1946, 1947) worked out a q u a n t i t a t i v e m u l t i s t a g e p r o c e s s so t h a t h i s c a l c u l a t e d c u r v e s f o r t h e r e g e n e r a t i o n of r h o d o p s i n o v e r t i m e c l o s e l y r e s e m b l e d e m p i r i c a l d a r k a d a p t a t i o n c u r v e s . A g a i n , h i s b a s i c a s s u m p t i o n was H e c h t i a n : t h r e s h o l d v a r i e s i n v e r s e l y w i t h t h e c o n c e n t r a t i o n of p h o t o s e n s i t i v e m a t e r i a l . R h o d o p s i n r e g e n e r a t i o n as an u n d e r l y i n g d e t e r m i n e r o f d a r k a d a p t a -t i o n t h r e s h o l d s was a s t r o n g c a n d i d a t e even i n 1876, s i n c e i t was,known t h a t i t s a c t i o n s p e c t r u m r e s e m b l e d t h e s u b j e c t i v e s c o t o p i c b r i g h t n e s s c u r v e once c o r r e c t i o n s f o r o c u l a r a b s o r p t i o n , a b s o r p t i o n by breakdown p r o -d u c t s , and the q u a n t i c i n t e n s i t y o f c o l o r e d l i g h t s were i n c l u d e d ( J a y l e , Ourgaud, B a r s i n g e r , Holmes, 1959). A l s o , C r a i k and Vernon (1941) r e a s o n e d t h a t n e u r a l e v e n t s c o u l d a c c o u n t f o r v e r y l i t t l e o f t h e d a r k a d a p t a t i o n s e n s i t i v i t y i n c r e a s e because t h e i r t i m e c o u r s e (3 min.) was so much s h o r t e r t h a n f u l l d a r k a d a p t a t i o n (30 m i n . ) . • But even i n 1940 L y t h g o e r a i s e d p u r e l y t h e o r e t i c a l d i f f i c u l t i e s f o r H e c h t i a n t h e o r i e s (LeGrahd, C h a p t e r 20) and p o i n t e d o u t t h a t i n any c a s e s m a l l changes i i n r h o d o p s i n c o n c e n t r a t i o n may be accompanied by d i s -p r o p o r t i o n a t e l y l a r g e changes i n t h r e s h o l d . Thompson.(1950) arg u e d s i m i -l a r l y t h a t even i f H e c h t ' s t h e o r y were c o m p a t i b l e w i t h e x i s t i n g e m p i r i c a l e v i d e n c e t h e e v i d e n c e c o u l d be h a n d l e d e q u a l l y w e l l by a l t e r n a t e h y p o t h e s e s , and he m a i n t a i n e d t h a t t h e l a c k o f c o m p lete r e c i p r o c i t y i n d a r k a d a p t a t i o n 57 between t i m e and i n t e n s i t y o f p r e - a d a p t a t i o n t e l l s a g a i n s t a p u r e p h o t o -c h e m i c a l mechanism. By now t h e r e i s a w e a l t h o f d a t a o p p o s i n g t h e o l d p h o t o c h e m i c a l t h e o r i e s , much o f i t i n t h e form o f d i s s o c i a t i n g t h r e s h o l d r i s e s o r f a l l s f r o m r h o d o p s i n c o n c e n t r a t i o n i n c r e a s e o r d e c r e a s e . F o r i n s t a n c e , P i r e n n e (LeGrand, C h a p t e r 20) d e m o n s t r a t e d t h a t even a t s u p r a t h r e s h o l d l e v e l s r h o d o p s i n a b s o r b s one p h o t o n v e r y s l o w l y , and Rusht o n ( L e G r a n d , C h a p t e r 20) f o u n d t h a t i f fewer t h a n 10% of t h e r o d s have a b s r o b e d a p h o t o n , t h e t h r e s h o l d goes up t h r e e t i m e s . .And a g a i n , G r a n i t e t a l . (Graham, C h a p t e r 8) found no d i r e c t r e l a t i o n s h i p between t h e r h o d o p s i n c o n c e n t r a t i o n o f the f r o g r e t i n a , w h i c h b e g i n s t o r i s e as soon as d a r k a d a p t a t i o n b e g i n s , and the e l e c t r i c a l r e s p o n s e w h i c h r e m a i n s c o n s t a n t u n t i l r h o d o p s i n c o n -c e n t r a t i o n r e a c h e s 50% o f i t s maximum. F i n a l l y , R u s h t o n (Graham, C h a p t e r 8). and h i s a s s o c i a t e s were a b l e t o d i r e c t l y measure r h o d o p s i n r e g e n e r a t i o n i n t h e human r e t i n a w i t h fundus r e f e c t o m e t r y and t h e y d e t e r m i n e d t h a t 7 min. a f t e r i n t e n s e b l e a c h i n g o f t h e pigment one h a l f had r e g e n e r a t e d , b u t th e r o d t h r e s h o l d was s t i l l 100 t i m e s h i g h e r t h a n the f i n a l t h r e s h o l d . L a t e r ( R u s h t o n , 1965a) t h e y showed d a r k a d a p t a t i o n . t o f o l l o w d i r e c t l y t h e p e r c e n t a g e of b l e a c h e d pigment s t i l l l e f t a f t e r b l e a c h i n g — a p o i n t d e v e l o p e d l a t e r i n t h i s s e c t i o n . Most c u r r e n t t h e o r i e s r e c o g n i z e t h a t somehow n e u r a l a d a p t a t i o n p a r t i c i p a t e s i n . t h e d e t e r m i n a t i o n o f d a r k a d a p t a t i o n t h r e s h o l d s , a l t h o u g h mechanisms can be c a t e g o r i z e d a c c o r d i n g t o emphasis i n t o p h o t o c h e m i c a l , 58 n e u r a l , and a c o m b i n a t i o n of t h e two. Wald (Graham, C h a p t e r 8) i s t h e p r i m a r y spokesman f o r a p u r e p h o t o c h e m i c a l mechanism t h a t r e l a t e s t h r e s h o l d t o t h e p r o b a b i l i t y o f a quantum h i t t i n g a r o d compartment (one r o d has s e v e r a l ) w i t h a f u l l c o n -c e n t r a t i o n of r h o d o p s i n . The h y p o t h e s i s i s c o m p a t i b l e w i t h h i s f i n d i n g t h a t l o g s e n s i t i v i t y i s p r o p o r t i o n a l t o r h o d o p s i n c o n c e n t r a t i o n , a l t h o u g h Weale"(1963). has c r i t i c i s e d e v i d e n c e f o r such a r e l a t i o n s h i p , and R u s h t o n has p l a c e d a d i f f e r e n t i n t e r p r e t a t i o n on i t (see b e l o w ) . B o t h Donner and R e u t e r ( 1 9 6 5 ) , and R u s h t o n (LeGrand, C h a p t e r 20) found t h a t a s i m p l e l o g a r i t h m i c f u n c t i o n d o e s n ' t o p e r a t e u n t i l 80% ( f r o g r e t i n a ) o r 90% (human r e t i n a ) o f t h e maximum r h o d o p s i n c o n c e n t r a t i o n i s a t t a i n e d i n the d a r k ; Donner and R e u t e r f u r t h e r f o u n d under c o n d i t i o n s e x c l u d i n g n e u r a l a d a p t a t i o n mechanisms t h a t l o g t h r e s h o l d i s l i n e a r l y r e -l a t e d t o l o g r a t e o f r e g e n e r a t i o n a t each moment i n t i m e . No one has p r o p o s e d a p u r e n e u r a l t h e o r y of d a r k a d a p t a t i o n , and v e r y o f t e n when i t i s c o n s i d e r e d as a component i t i s i n vague terms ( L e i b o v i c , 1 9 7 0 ) . Thompson (1950) supposed t h a t n e u r a l p r o c e s s e s a l t e r r e c e p t o r s e n s i t i v i t y t o b l e a c h e d p h o t o p i g m e n t s ; Graham ( C h a p t e r 8) s u g g e s t -ed t h a t changes i n i n h i b i t o r y p r o c e s s e s i n r e c e p t i v e f i e l d s o r i n c r e a s e s i n r e c e p t i v e f i e l d s i z e may o p e r a t e , , ••; V^n, and Arden and Weale (1954) s u p p o r t e d t h i s v i e w , i n an e x p e r i m e n t showing t h a t t h e i n t e g r a t i v e powers o f t h e r e t i n a i n c r e a s e d u r i n g d a r k a d a p t a t i o n as e v i d e n c e by t h e f a c i l i t a -t i v e e f f e c t s o f l a r g e r t e s t p a t c h s i z e s . 59 The most comprehensive theories have been worked out by. Barlow and Rushton, and their associates (Barlow, 1964a,b; Rushton, 1965; Rushton and Cohen, 1954; Rushton, Fulton and Baker, 1969; Rushton, 1965, Rushton, 1965a); interestingly, i n 1937 Crawford published data incorporating the theoretical precursor in the form of dark adaptation curves composed of an "equivalent background" and a differential intensity threshold i n time. Barlow and Rushton both see the dark adaptation threshold as the differen-t i a l threshold on top of a noisy background generated by bleached photo-pigments; as the pigment regenerates the noise i s reduced and the threshold drops. Rushton's analysis has even bleached rods excitable by a single quanta, but they contribute to a "summating pool" whose excitability i s inversely proportional to the amount of bleached pigment present. Somewhat opposed to the Barlow and Rushton theories i s Dowling's (1963) account which makes a sharp separation in time between early, rapid neural components, and later, slower photochemical components; the latter dominate the process of recovery, whereas the "noise" and "summating pool" mechanisms involved interaction between the components with neural events most powerful. Finally, the issue has become sufficiently complicated since Hecht's work for Bouman and Doesschate (1962) to analyse dark adapta-tion curves according to no fewer, than five separate processes in order to embrance a l l pre-adaptation and testflash variables. 60 The p r e c e d i n g d i s c u s s i o n c o n c e r n e d r o d mechanisms o f d a r k a d a p t a -t i o n ; p h o t o p i c mechanisms a r e more p o o r l y u n d e r s t o o d . The d a r k a d a p t a t i o n cone c u r v e , f o r i n s t a n c e i s f a s t e r t h a n t h e r o d c u r v e , and t h i s p r o b a b l y r e f l e c t s a f a s t e r r a t e o f pigment r e g e n e r a t i o n , b u t t h e r e a s o n s f o r cones o p e r a t i n g a t h i g h e r i n t e n s i t i e s .are t e n t a t i v e : t h e s e n s i t i v i t y d i f f e r a n c e d o e s n ' t r e p r e s e n t a l o w pigment c o n t e n t i n cones, as once was supposed ( L e G r a n d , C h a p t e r 20, A r d e n and Weale, 1954). Baumgardt (Le G r a n d , C h a p t e r 20) and A r d e n and Weale (1954) s u g g e s t e d t h a t cone s e n s i t i v i t y d i f f e r e n c e s as w e l l as " r e s i s t a n c e " t o b r i g h t l i g h t j compared t o r o d s o r i g i n a t e s from th e cones " p a r a l l e l " c i r c u i t r y compared t o t h e r o d s c o n v e r g i n g c i r c u i t r y . R u s h t o n has extended h i s i d e a s on s c o t o p i c a d a p t a t i o n t o p h o t o p i c as w e l l (DuCroz and R u s h t o n , 1966; R u s h t o n , 1 9 6 5 a ) , f i n d i n g t h r e e s e p a r a t e summating p o o l s f o r t h r e e cone m e c h a n i s m s — r e d , g r e e n and b l u e . M e n t i o n s h o u l d be made h e r e t h a t no cone pigments have been i s o l a t e d f r o m human, r e t i n a s , and t h r e e mechanisms are, j u s t t h a t — S t i l e s ' i n t e r p r e t a t i o n f r o m t h r e s h o l d i n c r e m e n t s t u d i e s and Rushton's f r o m fundus r e f l e c t o m e t r y , f o r i n s t a n c e . R i n a l d u c c i (1968) has ex t e n d e d B a r l o w ' s . " n o i s e " mechanism t o cones w i t h the a d d i t i o n o f some w a v e l e n g t h - s p e c i f i c r e c e p t i v e f i e l d r e o r g a n i z a -t i o n t h a t o p e r a t e s m o s t l y i n t h e p h o t o p i c phase i n the. f o r m o f a h i g h e r r a t i o o f i n h i b i t i o n t o e x c i t a t i o n on a d a r k r e t i n a compared t o a ^ l i g h t one. He a l s o f i n d s more i n t e r a c t i o n among r e c e p t o r s e a r l y i n d a r k a d a p t a -t i o n t h a n l a t e . 61 C e n t r a l t o t h e methods of t h i s t h e s i s i s t h e s h i f t t h a t o c c u r s d u r i n g d a r k a d a p t a t i o n from t h e p h o t o p i c t o s c o t o p i c system. Because r o d s and cones have d i f f e r e n t s p e c t r a l s e n s i t i v i t i e s ( r o d s a r e f a v o r e d by t h e s h o r t e r , cones by the l o n g e r w a v e l e n g t h s ) t h e e f f e c t o f w a v e l e n g t h on d a r k a d a p t a t i o n t h r e s h o l d may be e x p e c t e d t o change w i t h t i m e i n t h e d a r k ; t h e u n d e r l y i n g p r o c e s s e s a t work make up the " P u r k i n j e s h i f t " w h i c h o c c u p i e s p a r t o f t h e i n t e n s i t y and t i m e c o n t i n u a o f d a r k a d a p t a t i o n — n a m e l y , t h o s e p a r t s (mesopic) t h a t r e p r e s e n t n e i t h e r p u r e r o d ( s c o t o p i c ) n o r p u r e cone ( p h o t o p i c ) p r o c e s s e s . There has been some i n t e r e s t i n w o r k i n g o u t t h e r e l a t i o n s h i p s between r o d s and cones r e g a r d i n g t h e i r p a r t i c i p a t i o n i n d e t e r m i n i n g d a r k a d a p t a t i o n t h r e s h o l d s i n a l l t h r e e s e c t i o n s ( p h o t o p i c , m e s o p i c , s c o t o p i c ) . V a r i o u s r e a s o n s have been g i v e n f o r t h e d o m i n a t i n g a c t i v i t y o f cones e a r l y i n d a r k a d a p t a t i o n : (1) cone p h o t o p i g m e n t s r e g e n e r a t e f a s t e r t h a n r h o d o p s i n ; (2) t h e p a r a l l e l c i r c u i t r y o f cones t o t h e i r n e u r ons " p r o t e c t s " t h e neuron, from r e f r a c t o r i n e s s , (3) l i g h t a d a p t a t i o n c a u s e s t h e cones t o m o n o p o l i z e n e u r a l pathways ( L i p e t z , 1 9 6 2 ) , (4) r h o d o p s i n i n low c o n c e n t r a t i o n s may a c t u a l l y be a c t i v e a t l e v e l s u s u a l l y a s c r i b e d t o cones and p a r t i c i p a t e i n t h r e s h o l d d e t e r m i n a t i o n s ( a s c r i b e d • t o G r a n i t by Graham., Ch a p t e r 8 ) . There i s some r e a s o n t o b e l i e v e t h a t r o d s a c t i v e l y i n h i b i t cones d u r i n g t h e . s c o t o p i c phase o f d a r k a d a p t a t i o n , b u t t h e e v i d e n c e i s i n c o n -c l u s i v e . Dodt and J e s s e n (1960) c i t e some e a r l y s t u d i e s s u p p o r t i n g t h e i r 62 f i n d i n g o f cone s u p p r e s s i o n i n f r o g eyes c o r r e s p o n d i n g t o t h e t i m e t h a t r o d s s u d d e n l y i n c r e a s e d t h e i r a c t i v i t y , a l t h o u g h Brown, Metz and Yokman (1969) f a i l e d t o o b t a i n ah e q u i v a l e n t e f f e c t i n human d a r k a d a p t a t i o n c u r v e s , t h e a l t e r n a t i v e t o a c t i v e cone s u p p r e s s i o n w o u l d be f o r t h e most s e n s i t i v e r e c e p t o r ( i . e . r o d s l a t e i n d a r k a d a p t a t i o n ) t o d e t e r m i n e t h e t h r e s h o l d . Gouras' (1965) and Gouras and L i n k ' s (1966) work i s c o m p a t i b l e w i t h t h i s i d e a , a l t h o u g h i t d o e s n ' t e x c l u d e n e u r a l i n h i b i t i o n o f cones by r o d s b e f o r e t h e g a n g l i o n c e l l l e v e l . W a l t e r s and W r i g h t (1943) s u g g e s t e d t h a t r o d s may h o l d sway.because as i n t e n s i t y d e c r e a s e s summa-t i o n i s f a v o r e d and r o d s have c o n v e r g i n g c o n n e c t i o n s t o n e u r o n s , whereas cones do n o t . Rod i n f l u e n c e s s i m p l y d i m i n i s h more g r a d u a l l y t h a n cone i n f l u e n c e s as i n t e n s i t y d i m i n i s h e s . On t h e o t h e r hand, Wald (1960, 1961, p e r s o n a l communication t o R. L a k o w s k i ) c o n c l u d e s , p a r t l y on t h e b a s i s o f a m e a s u r a b l e S.'tiles-Crawford e f f e c t l a t e i n d a r k a d a p t a t i o n , t h a t cones . p a r t i c i p a t e i n t h r e s h o l d r e s p o n s e s d u r i n g t h e s c o t o p i c phase. The most, debate d i s s u e about t h e t r a n s f e r of cone f u n c t i o n t o r o d f u n c t i o n i n t h e m esopic p o r t i o n o f t h e c u r v e i s whether r o d s and cones i n t e r a c t . 1 Wald t h i n k s t h e y do (Wald, 1960, 1961, p e r s o n a l communi-c a t i o n t o R. L a k o w s k i ) w i t h v a r y i n g p r o p o r t i o n s • o f cone and r o d components 'ente r i n g t h e r e s p o n s e as time goes on i n t h e d a r k ; t h e w a v e l e n g t h of t h e t e s t f l a s h m a t t e r s s i n c e r o d s dominate, s h o r t w a v e l e n g t h components o f t h e s t i m u l u s f i r s t , and t h e n t h e l o n g e r . Bridgman (1960, 1953) sees t h e 63 transfer as taking-place a l l at once; short wavelength components are taken over by rods'at a certain point in time, then longer components move under their influence; rod and cone interaction i s restricted to some summation at wavelengths where their sensitivities are equal—a wavelength that is ever changing for both receptors as dark adaptation progresses. 64 i n OBJECTIVES OF THIS STUDY A. G e n e r a l C o n s i d e r a t i o n s F o r s e v e r a l y e a r s now i t has been known t h a t open a n g l e glaucoma i s o f t e n accompanied by c o l o r v i s i o n l o s s e s ( f o r i n s t a n c e , see V e r r i e s t , 1964 o r F r a n c o i s and V e r r i e s t , 1968) as w e l l as d a r k a d a p t a t i o n d e f i c i e n -c i e s . I n f a c t , F r a n c o i s , and V e r r i e s t (1961) s t a t e t h a t one d i f f e r e n c e between c o n g e n i t a l and a c q u i r e d d y s c h r o m a t o p s i a s i s t h a t t h e l a t t e r g e n e r a l l y o c c u r s a l o n g w i t h i m p a i r m e n t s o f o t h e r v i s u a l f u n c t i o n s s u c h as da r k a d a p t a t i o n . R e c e n t l y , L a k o w s k i , Bryett;.; and Drance (1972) d e m o n s t r a t e d t h a t o c u l a r h y p e r t e n s i v e s c h a r a c t e r i z e d by r a i s e d p r e s s u r e s , b u t n o r m a l a c u i t y , n o r m a l d i s c s , and f u l l v i s u a l f i e l d s , n e v e r t h e l e s s show c o l o r v i s i o n d e f i c i t s g r e a t e r than e q u i v a l e n t age group c o n t r o l s . The p r e s e n t t e c h -n i q u e can be v i e w e d as an i n v e s t i g a t i o n of an h y p o t h e s i s t h a t n a t u r a l l y f o l l o w s f r o m t h e s e r e s u l t s , namely, t h a t s i n c e c o l o r v i s i o n i s h a n d l e d by f o v e a ! c o n e s , i f d a r k a d a p t a t i o n i s made t o i n v o l v e t h e s e r e c e p t o r s by a r r a n g i n g the t e s t a r e a and s p e c t r a l c o m p o s i t i o n o f t h e l i g h t a p p r o p r i a t e -l y , t h e n once a g a i n eyes w i t h e a r l y open a n g l e glaucoma s h o u l d show d i f -f e r e n c e s f r o m t h e i r n o r m a l c o u n t e r p a r t s . T h i s r e a s o n i n g i s a p p r o p r i a t e , o f c o u r s e , o n l y i n s o f a r . a s common p r o c e s s e s , s t r u c t u r e s , o r f u n c t i o n a l 65 r e l a t i o n s o p e r a t e t o d e t e r m i n e p e r f o r m a n c e on c o l o r v i s i o n t e s t s and d a r k a d a p t a t i o n t e s t s ; f a i l u r e t o f i n d c e r t a i n p r e d i c t e d changes w o u l d s u g g e s t e i t h e r t h a t the s e p a r a t e t e s t s a r e t a p p i n g phenomena t h a t a r e n o t r e l a t e d o r t h a t t h e t e s t s t h e m s e l v e s have f a i l e d t o engage what i s i n f a c t s h a r e d i n common by c o l o r v i s i o n and d a r k a d a p t a t i o n . The p r e s e n t e x p e r i m e n t can a l s o s t a n d a l o n e i n t h a t c o m p a r i s o n s between o c u l a r h y p e r t e n s i v e s and n o r m a l s u b j e c t s on a v a r i e t y o f d a r k a d a p t a t i o n and c o l o r v i s i o n v a r i a b l e s may be made w i t h o u t r e g a r d t o t h e p r e v i o u s c o l o r v i s i o n s t u d y . A d d i t i o n a l l y , d i f f e r e n c e s i n c o l o r v i s i o n between t h e two groups w i l l c o n f i r m o r c o n f l i c t w i t h t h e L a k o w s k i , e t a l . s t u d y i n a d i r e c t , a l t h o u g h r e s t r i c t e d way. S i g n i f i c a n t d i f f e r e n c e s found f o r d a r k a d a p t a t i o n v a r i a b l e s can be a p p l i e d as e v i d e n c e f o r o r a g a i n s t e x i s t i n g t h e o r i e s about mechanisms o f open a n g l e glaucoma and may go toward t h e development o f a new d i a g n o s t i c t o o l . ' F i n a l l y , a v a r i e t y of c l i n i c a l measures on t h e h y p e r t e n s i v e g r o u p , some s p e c i f i c a l l y o p h t h a m o l o g i c a l , some n o t , w e r e . a v a i l a b l e and a r e used h e r e f o r c o r r e l a t i o n s w i t h d a r k a d a p t a t i o n measures. S u b j e c t s were p r e -s e l e c t e d on s e v e r a l v a r i a b l e s , so c o r r e l a t i o n s i n v o l v i n g them a r e e x p e c t e d t o be low. Once a g a i n , . s i g n i f i c a n t c o r r e l a t i o n s can be used t o enhance th e c r e d i b i l i t y o f a p p r o p r i a t e t h e o r i e s a c c o u n t i n g f o r t h e o n s e t and de-velopment o f open a n g l e glaucoma. The most c o n v i n c i n g e v i d e n c e f o r arguments about mechanisms and the most p e r s u a s i v e a p p e a l f o r t h e i n c l u s i o n o f d a r k a d a p t a t i o n t e c h n i q u e s i n the d i a g n o s t i c armament woul d come from f o l l o w - u p s t u d i e s on t h e s e 6 6 o c u l a r h y p e r t e n s i v e s . Do dark a d a p t a t i o n measures, p o s s i b l y i n combina-t i o n w i t h c o l o r v i s i o n assessments improve the p r e d i c t a b i l i t y of f u l l -blown glaucoma•beyond present p r e d i c t a b i l i t y on the b a s i s of t r a d i t i o n a l c l i n i c a l measures? Do they c o n t r i b u t e to an accurate prognos i s? Not enough time has passed f o r such a s t u d y , but t e n t a t i v e .suggest ions can be made based on a separate group of s u b j e c t s w i t h e s t a b l i s h e d open angle glaucoma who have had t h e i r dark a d a p t a t i o n and c o l o r v i s i o n measured. B.- The T h e o r e t i c a l Framework . From the most g e n e r a l overview of the survey of the dark a d a p t a t i o n l i t e r a t u r e emerges a u n i f y i n g p r i n c i p l e t h a t has been a p p l i e d to many v i s u a l processes s i n c e the end of the l a s t c e n t u r y , and i s r e f e r r e d to as the duplex nature of the r e t i n a . Many t h e o r e t i c a l and p r a c t i c a l a s -pects of the present technique can be seen as a l l o w i n g f o r and t a k i n g a d -vantage of t h i s a n a t o m i c a l and f u n c t i o n a l d u a l i t y . For the present experiment we w i s h to i n v o l v e both the rod and the cone systems, p a r t i c u l a r l y w i t h r e f e r e n c e to the P u r k i n j e s h i f t ; cones i n order to f o l l o w - u p the L a k o w s k i , e t a l . work, and rods because the a d d i -t i o n a l system p l u s the i n t e r a c t i o n of the two can be expected to p r o v i d e more k i n d s of i n f o r m a t i o n than a s i n g l e system. A c o n s i d e r a t i o n of the v a r i a b l e s composing a dark a d a p t a t i o n experiment shows why the human r e t i n a has been d e s c r i b e d as a n i g h t rod r e t i n a interwoven w i t h a day cone r e t i n a . 67 (1) P r e - a d a p t a t i o n i n t e n s i t y arid d u r a t i o n The c o m b i n a t i o n o f t h e two must be g r e a t enough t o i n v o l v e cones i n p r e - a d a p t a t i o n , b u t n o t so g r e a t as t o p l a c e an i n i t i a l t h r e s h o l d o f f t h e upper s c a l e l i m i t s of t h e t e s t i n g a p p a r a t u s . A d d i t i o n a l l y , t h e r a t e o f change of the t h r e s h o l d s h o u l d n o t be so g r e a t as t o be d i f f i c u l t t o r e c o r d a c c u r a t e l y , n o r s h o u l d t h e cone s e c t i o n be so b r i e f as t o occupy o n l y t h e f i r s t few s e c o n d s , w h i c h may b e . l o s t due t o s u b j e c t u n c e r t a i n t y . S i n c e t h i s i s a c l i n i c a l s t u d y . a t t e n t i o n must be g i v e n t o s u b j e c t c o m f o r t , as an i r r i t a b l e s u b j e c t can make t h e d a t a so u n r e l i a b l e as t o b e 1 u s e l e s s . I n t e n s i t y and d u r a t i o n o f p r e - a d a p t a t i o n must t h e r e f o r e be b a l a n c e d so the c o m b i n a t i o n i s n ' t o v e r l y demanding o f the s u b j e c t ' s p a -t i e n c e . Nor s h o u l d t h e t i m e i n t h e d a r k r e q u i r e d t o r e a c h a f i n a l s t a b l e ( o r a l m o s t s t a b l e ) t h r e s h o l d be too l o n g . (2) P r e - a d a p t a t i o n p a t t e r n , - s i z e , and l o c a t i o n F o r t u n a t e l y t h e s e v a r i a b l e s a r e n o t p a r t i c u l a r l y c r i t i c a l t o j u d g e from t h e l i t e r a t u r e , b e c a u s e t h e y a r e p o o r l y u n d e r s t o o d . I t i s s u f f i c i e n t t h a t t h e p r e - a d a p t e d a r e a be superimposed upon and a t l e a s t as l a r g e as the a r e a t o be t e s t e d d u r i n g d a r k a d a p t a t i o n , so t h a t the a r e a t e s t e d d u r -i n g r e c o v e r y has been s u b j e c t e d t o a known amount o f l i g h t b e f o r e h a n d . The most c o n s e r v a t i v e p r e - a d a p t a t i o n i s t h e a l m o s t f u l l - f i e l d p r o v i d e d by a p h o t o m e t r i c s p h e r e , because i t p a r t l y r e d u c e s the e f f e c t s o f a f t e r images t h a t appear most t r o u b l e s o m e d u r i n g d a r k a d a p t a t i o n a f t e r p r e - a d a p t a t i o n of s m a l l e r a r e a s r e q u i r i n g f i x a t i o n . 68 (3) C o l o r ' of p r e - a d a p t a t i o n arid t e s t l i g h t . T h i s i s t h e s i n g l e most i m p o r t a n t d i m e n s i o n i n t h e p r e s e n t s t u d y , and an a p p r e c i a t i o n of i t s u t i l i t y can be g l e a n e d f r o m Wald's (1960) method, which,- as i n t h i s s t u d y , i s based on t h e CIE l u m i n o s i t y c u r v e s f o r r o d s and cones ("Figure 1(0) . —3 2 —6 2 A t a p p r o p r i a t e i n t e n s i t y l e v e l s (10 cd/m t o 10 cd/m ) d a r k a d a p t e d r o d s f u n c t i o n most e f f i c i e n t l y w i t h a s t i m u l u s around 510 mn, a t ~A 2 2 p h o t o p i c l e v e l s (3x10 cd/m t o 10 cd/m ) l i g h t a dapted cones dominate and.are most s e n s i t i v e t o l i g h t around 555 njtt. ' The r e s p o n s e of a l i g h t -a dapted r e t i n a p l u n g e d i n t o d a r k n e s s depends, t h e n , p a r t l y on t h e wave-l e n g t h of the p r e - a d a p t i n g and t e s t l i g h t s . M o r e o v e r , t h e e f f i c i e n c y o f a l i g h t o f a c e r t a i n s p e c t r a l c o m p o s i t i o n w i l l change as r o d s b e g i n t o dominate t h e r e s p o n s e ; a q u a n t i t a t i v e measure of t h i s change (i.e«, th e P u r k i n j e s h i f t ) can be o b t a i n e d b y . r e c o r d i n g t h e r e l a t i v e d a r k a d a p t a t i o n t h r e s h o l d changes f o r two d i f f e r e n t l y c o l o r e d l i g h t s t h a t were o r i g i n a l l y e q u a l i n e f f i c i e n c y d u r i n g p r e - a d a p t a t i o n ( i . e . ^ w e r e p h o t o p i c a l l y e q u i v a -l e n t w i t h r e f e r e n c e t o t h e CIE c u r v e o r e q u a t e d f o r b r i g h t n e s s by t h e l i g h t - a d a p t e d e y e ) . W i t h r e f e r e n c e t o F i g u r e 11 now, c o n s i d e r two monochromatic l i g h t s , ',4^  and They s t i m u l a t e cones e q u a l l y w e l l , b u t s t i m u l a t e s r o d s more e f f i c i e n t l y t h a n ^ does. and "Z^ a r e e quated p h o t o p i c a l l y f o r b r i g h t n e s s under e q u a l e n e r g y c o n d i t i o n s d u r i n g l i g h t a d a p t a t i o n . Then i f we measure t h e l i g h t i n c i d e n t on t h e c o l o r e d f i l t e r s d u r i n g d a r k i - j -—l— i ' —Tl ;.:. —1 _ !::: :::: . h : , ; ; . i —- • 1 — ~\r— _ „ 1__„ ^ _ ;. :: _____ - f — '• i — J — — i ' • i-• 1 — I j < _ \ j - . r : : - / 1 j H 1 fli 1 o : _ • - J -<_ "TfTT ;: \ P H — - — I -. I ' . I . . 1 f" :: — - i — ! j f 1.3 - : 3 im —1 • • « -A4»-_ _li __ _ _ >o ng,t—- ' -. 1J U '_u_n:ra_, *n•• t /.~• -. . . —~kW / J :>«: fO 7 _ — 5 cm* 4 (?. [ j^_#eS '* . . . » i; ' . ' ' ..... _! _ j — S h u (.,: 1 i V<Jl\0 ML C \ . YsU V ••;| •-. jkfe • i ~—rtt '.I'.: ;;i: [\.'_ • _ •<'•• . . j , ... : . iir; :;:: : I i: ;;  : :;.:: :;:: :;: i : • ^ ]] ______ \Zi '_ ' i .i:! :::; • ::: ^ :!: r .rj:: . j.:.: :: |-j !Pi-! jlll iff! i •! • • i i '-rtt ;41-i Si] ill: . j III:. rr:: : : : : ! : ! -J-i -'•-'} F # % ill. Ii M r|;: i : • • •III 1 :l "ill ii!? : : : • ":;1. li.i'1 ... — • •;r:t •.ft'-• . : : : •1-1"' ii:: ^il IIII : : : : ; : ; : ; : -iiii : : ; : | ; » / i i I l -e>_ P I j /•» V a a ^. I i - : ; : : • H) V / 1 iii* * I • 1 1 •* — 0 ! tow en* ik f/H M - f t ,l.:U, :-:-:: •' 1: : :li ..I .£ fift e ft V Oft 'II 1& // r , • j : :: v. / u % /'• /ft 9 .:{ ; ' : * t. , • •• : | i | ! • ... III: .. 1. ' •: i. : i Hi; :ii:l j-i-i-r 71 adaptation, i f the and test patches, are photopically equal for the highest test intensity, the Jt^  f i l ter wil l in i t ia l ly require less; as rods-begin to function ^£ wil l require less relative to /{^  and the two dark adaptation curves wil l cross with the curve finally lying below the ^ . ••• . . , •• Three points governed the selection of ^£ and ^U^ : (1) this twb-f i l ter method "was first used successfully on a clinical Cdiabetic) popula-tion by Gill (1966) and there are practical advantages in following his choice of wavelengths, which was arrived at after considerable preliminary testing with a similar adaptometer. ( 2 ) A m o n g other things, G i l l found a large (0.5 log unit) maximum separation between the two dark adaptation curves in a normal population with yellow and blue-green light; and fit ^ must, of course, follow the rod-cone relations illustrated in Figure 'Dl'1 , but beyond that, a large curve separation is a l l to the good in a popula-tion study because i t wil l allow for individual variation that could tend to reduce the separation, and consequently erase the display of the sought-, after spectral sensitivity shift. (3) The'effec ts of dark adaptation of pre-retinal changes (e.g.,yellowing of the ocular media with age or disease) and individual variations of yellow macular pigment concentration (which absorbs strongly in the short wavelengths and may cause irregularities in the curve of photopic luminous efficiency at the short end of the spectrum) are minimized when yellow light is the stimulus, and.so may be eliminated 72 as causes o f changes i n ftie (k,^ d a r k a d a p t a t i o n c u r v e w i t h i n a c l i n i c a l p o p u l a t i o n . B o t h r o d and cone p o r t i o n s of a • , BG.p .TX'dark a d a p t a t i o n c u r v e , on t h e o t h e r hand, w i l l be more a f f e c t e d t h a n t h e Y c u r v e by the f a c t o r s m e n t i o n e d above; . I n a d d i t i o n , t h e r e i s e v i d e n c e ( L a k o w s k i e t a l . , 1972) t h a t e a r l y open a n g l e glaucoma i s o f t e n c o i n c i d e n t w i t h d i s t u r b a n c e s i n c o l o r v i s i o n r e l a t e d to s h o r t w a v e l e n g t h p r o c e s s e s . T h i s l a s t f a c t o r w o u l d be e x p e c t e d t o i n f l u e n c e t h e cone p o r t i o n o f t h e ^ c u r v e . A l t h o u g h the f a c t o r s r e s p o n s i b l e f o r d i f f e r e n c e s between c o n t r o l and c l i n i c a l BG c u r v e s may p r o v e d i f f i c u l t t o i s o l a t e , n o n e t h e l e s s , t h e . chances f o r o b t a i n i n g a s i g n i f i c a n t d i f f e r e n c e have been m a x i m i z e d . I n c i -d e n t a l l y , any d i f f e r e n c e s between n o r m a l and c l i n i c a l p o p u l a t i o n s r e g a r d -i n g BG Y - c u r v e s e p a r a t i o n w i l l l i k e w i s e be made t o s t a n d o u t . (4) T e s t f i e l d l o c a t i o n , s i z e and d u r a t i o n ' I n o r d e r t o engage f o v e a l cones f i x a t i o n must be c e n t r a l . The p o i n t h e r e i s t o i n v e s t i g a t e the same a r e a c o l o r v i s i o n t e s t s examine and a d d i t i o n a l l y t o - f i n d s u p p o r t • f o r t h e more g e n e r a l i d e a t h a t , c o n t r a r y t o the a c c e p t e d a c c o u n t o f t h e development o f glaucoma i n w h i c h t h e f o v e a i s t h e l a s t a r e a t o f a i l (as j u d g e d by p e r i m e t r y ) , w i t h an a p p r o p r i a t e k i n d o f m e a s u r i n g t o o l ( i . e . d a r k a d a p t a t i o n ) , c e n t r a l a r e a s may be shown t o de-t e r i o r a t e e a r l y i n the c o u r s e o f t h e d i s e a s e . To p r o v i d e f o r r o d p a r t i c i -p a t i o n t h e t e s t p a t c h must e x t e n d b.eyond t h e 2^ r o d - r f r e e a r e a . 73 Here a g a i n , G i l l (1966) i n v e s t i g a t e d c i r c u l a r t e s t p a t c h e s up t o 11° i n d i a m e t e r , w h i c h i s t h e l a r g e s t h a n d l e d by t h e p a r t i c u l a r adaptome-t e r used h e r e . He fo u n d 11° t o g i v e t h e most r e l i a b l e and w e l l - d e f i n e d c r o s s - o v e r p o i n t . F u r t h e r , t h e r e i s one t h e o r e t i c a l r e a s o n f o r u s i n g 11°— namely, t h a t i t j u s t i n c l u d e s t h e s t e e p , , g r a d i e n t s f o r r o d and cone d e n s i -t y a c r o s s t h e r e t i n a . D i s t u r b a n c e s i n ro d - c o n e i n t e r a c t i o n m i g h t be e x -p e c t e d t o r e v e a l t h e m s e l v e s h e r e b e t t e r t h a n i n t e s t a r e a s c h a r a c t e r i z e d by i n c l u s i o n o f i n c o m p l e t e g r a d i e n t s . T h i s may be, i n f a c t , t h e e x p l a n a -t i o n f o r G i l l s o b s e r v a t i o n s w i t h v a r i o u s s i z e s o f t e s t p a t c h . S e l e c t i o n o f t e s t f l a s h d u r a t i o n was g u i d e d by p u r e l y p r a c t i c a l c o n s i d e r a t i o n s : t h e a p p a r a t u s i s d e s i g n e d w i t h a r o t a t i n g •diaphram.iKG t h a t o p e r a t e s w i t h a one-second e x p o s u r e . A l t h o u g h t h e diaphram may be c l o s e d c o m p l e t e l y f o r any l e n g t h o f ti m e d u r i n g d a r k a d a p t a t i o n , d e t a i l s o f t h e t e s t f i e l d i n t e n s i t y c o n t r o l r e q u i r e d t h a t t he f l a s h be on f o r one s e c o n d , o f f f o r t h e n e x t , and so o n , c o n t i n u o u s l y . Such a p r o c e d u r e may o r may not have i n t r o d u c e d , a s i g n i f i c a n t , amount o f l i g h t a d a p t a t i o n d u r i n g d a r k a d a p t a t i o n t e s t i n g , b u t i t ' s u n i m p o r t a n t s i n c e any b l e a c h i n g i s e q u i v a l e n t f o r t h e BG (<$) Y c o n d i t i o n s f o r any p a r t i c u l a r s u b j e c t . (5) P u p i l D i a m e t e r No.attempt was made t o c o n t r o l f o r t h e s i z e o f the s u b j e c t s ' p u p i l s , e x c e p t w i t h s t a t i s t i c a l p r o c e d u r e s t h a t b r o k e c l i n i c a l and n o r m a l p o p u l a t i o n s i n t o two. age groups.' The r e a s o n s a r e o b v i o u s f r o m t h e s u r v e y o f t he l i t e r a t u r e (p. 37 )» p a r t i c u l a r l y w i t h r e f e r e n c e t o Z b a r s k i i (1958). 74 (6) Age I n some ways t h i s i s t h e m o s t . t r o u b l e s o m e f a c t o r s i n c e t h e some-t i m e s - r e p o r t e d i n c r e a s e i n v a r i a b i l i t y o f t h r e s h o l d w i t h age w i t h i n a p o p u l a t i o n i s l i k e l y t o h a n d i c a p a t t e m p t s t o f i n d s i g n i f i c a n t d i f f e r e n c e s between c l i n i c a l and c o n t r o l p o p u l a t i o n s even though c o m p a r i s o n s a r e made, as i n t h i s s t u d y , between e q u i v a l e n t age g r o u p s . I t w i l l be i n t e r e s t i n g t o see i f y e l l o w l i g h t w i l l r e d u c e t h e v a r i a b i l i t y whose cause might be an.uneven d i s t r i b u t i o n o f media y e l l o w i n g i n o l d e r age groups. F u r t h e r , t h e c o n t r o l , p o p u l a t i o n can be s p l i t b e -tween s u b j e c t s s c r e e n e d by an o p h t h a l m o l o g i s t and v o l u n t e e r s c o l l e c t e d by the e x p e r i m e n t e r . S c reened s u b j e c t s had no c o n d i t i o n known t o a f f e c t d a r k a d a p t a t i o n ( e . g . , D i a b e t e s , c a t a r a c t ) , and may t h e r e f o r e show l e s s t h r e s h o l d v a r i a b i l i t y t h a n t h e v o l u n t e e r group whose d i s e a s e h i s t o r y was m o s t l y un-known t o t h e e x p e r i m e n t e r . To Summarize By n o w . i t i s a p p a r e n t t h a t t h e two d a r k a d a p t a t i o n c u r v e s g e n e r a -t e d a s ' s e t out above w i l l r e s u l t i n a l a r g e a r r a y o f v a r i a b l e s . F i g u r e smoothed o r unsmooth sample o f two curves,: (Y & BG) i s an example of one s u b j e c t s r e s u l t s f o r i l l u s t r a t i o n . A l l t h e s e v a r i a b l e s a r e o b t a i n a b l e , f r o m two s u c h c u r v e s ; a l l . n o r -m a l s u b j e c t s and o c u l a r h y p e r t e n s i v e s p e r f o r m e d t h e d a r k a d a p t a t i o n t e s t s : 75 1) t h r e s h o l d each m i n u t e , BG & Y c u r v e s , 2) r a t e o f t h r e s h o l d change e a c h m i n u t e , BG Y c u r v e s , 3) c r o s s - o v e r t i m e , 4) c r o s s — o v e r i n t e n s i t y , 5) t h r e s h o l d v a r i a b i l i t y e a ch m i n . , BG Y - c u r v e s , 6) . change i n t h r e s h o l d v a r i a b i l i t y e a c h min. ,- BG Y c u r v e s , >' 7) s e p a r a t i o n between BG & Y c u r v e s e a c h min,, 8) r a t e o f change of s e p a r a t i o n between BG$< Y c u r v e s each min. Some, b u t n o t a l l o f t h e s e v a r i a b l e s were examined by G i l l . I n a d d i t i o n , a g e , . s e x , a c u i t y , and s c o r e s on the F a r n s w o r t h -M u n s e l l 100-Hue T e s t f o r c o l o r d i s c r i m i n a t i o n , , o n t h e I s h i h a r a pseudo-c h r o m a t i c p l a t e s , and.on the Tokyo M e d i c a l C o l l e g e c o l o r v i s i o n t e s t were c o l l e c t e d f o r a l l n o r m a l c o n t r o l s . The r e m a i n i n g measurements, w h i c h were net made by t h i s e x p e r i m e n t e r were s u p p l i e d f o r the h y p e r t e n s i v e group o n l y : 1) b l o o d p r e s s u r e , 2) s c o r e s on the F a r n s w o r t h P a n e l D-15 dichotomous t e s t , 3) -scores on the D v o r i n e p s e u d o i s o c h r o m a t i c p l a t e s , . 4) P i e k f o r d - N i c o l o s O n anomaloscope m a t c h i n g r a n g e s and m i d p o i n t s f o r t h e r e d - g r e e n , y e l l o w - b l u e , and b l u e - g r e e n e q u a t i o n s , 5) h i g h e s t r e c o r d e d i n t r a o c u l a r p r e s s u r e /' and/or l i m i t s o f t h e r e c o r d e d p r e s s u r e s , 76 6) m a c u l a r s e n s i t i v i t y as o b t a i n e d by p e r i m e t r y , 7) f a m i l y h i s t o r y of glaucoma 8) c o n d i t i o n o f t h e o p t i c d i s c , 9) o t h e r d i s e a s e s t h e . s u b j e c t was known t o have. Viewed as an i n d e p e n d e n t s t u d y j t h i s e x p e r i m e n t s h o u l d be more l i k e l y t o f i n d d a r k a d a p t a t i o n d i f f e r e n c e s between n o r m a l s and o c u l a r h y p e r t e n s i v e s t h a n p r e v i o u s s t u d i e s s i m p l y b e c a u s e i t g e n e r a t e s so many more v a r i a b l e s t h a t o r i g i n a t e s i n g l y from p r o c e s s e s w h i c h i n c o m b i n a t i o n p roduce t h e t r a d i t i o n a l d a r k a d a p t a t i o n c u r v e . I n f o l l o w i n g up t h e L a k o w s k i , e t a l . , s t u d y , we m i g h t e x p e c t r a i s e d BG cone t h r e s h o l d s f o r h y p e r t e n s i v e s compared t o nor m a l s a n d ^ p o s s i b l y ' a s l o w e r r a t e o f change f o r t h a t s e c t i o n . ' E a r l y c r o s s - o v e r t i m e s , e s p e -c i a l l y among h y p e r t e n s i v e s w i t h l a r g e c o l o r - v i s i o n l o s s e s may a p p e a r , i f , as G i l l s u g g e s t s ; s u c h t i m e s a r e i n d i c a t i v e o f l o s s o f cone f u n c t i o n . F i n a l l y , anomaloscope m i d - m a t c h i n g p o i n t s - a n d m a t c h i n g r a n g e s f o r t h r e e c o l o r e q u a t i o n s as w e l l as s c o r e s on the 100-Hue. were found t o d i f f e r i n o c u l a r h y p e r t e n s i v e s compared t o n o r m a l s , arid t h e y a r e e x p e c t e d t o c o r r e -l a t e w i t h cone d a r k a d a p t a t i o n v a r i a b l e s , whereas s c o r e s ' o n the I s h i h a r a , w h i c h d o e s n ' t d i s t i n g u i s h between h y p e r t e n s i v e s and n o r m a l s a r e n o t ex-, p e c t e d t o c o r r e l a t e . As f a r as - t h e o r i e s a b o u t open a n g l e glaucoma o n s e t a r e c o n c e r n e d , a r a i s e d IOP mechanism wou l d be f a v o r e d and v a s c u l a r t h e o r i e s weakened by 77 an a s s o c i a t i o n between dark adap ta t ion l o s s e s and pressure range or maximum recorded p re s su re ; a s t rong a s s o c i a t i o n between b lood pressure and dark adap ta t i on d e f i c i t s would s t rengthen v a s c u l a r t h e o r i e s . ' 78 IV APPARATUS A l l d a r k a d a p t a t i o n t e s t s were c a r r i e d o ut o v e r m o d i f i e d Goldmann-Weekers a d a p t o m e t e r , m a n u f a c t u r e d by H a g g - S t r e i t . The i n s t r u m e n t , as i t a r r i v e s from the m a n u f a c t u r e r , p r o v i d e s t h r e e e s s e n t i a l elements:. (1) a means t o p r e - a d a p t each s u b j e c t ' s eyes t o a c o n s t a n t amount of l i g h t ; (2) a way t o p r e s e n t t h e t e s t f l a s h a t a c o n s t a n t . l'6G:a#ion<and-.a-rea-j, a v a r i a b l e i n t e n s i t y , and a t a p a r t i c u l a r p l a c e on t h e r e t i n a ; a way t o r e c o r d t h r e s h o l d i n t e n s i t y a g a i n s t t i m e i i i t h e d a r k . Some o f t h e m o d i f i c a t i o n s r e l a t e t o t h e o r e t i c a l f a c t o r s as p r e -v i o u s l y d i s c u s s e d , O t h e r s t o more p r a c t i c a l m a t t e r s . Some were worked ou t by G i l l , o t h e r s by the a u t h o r . P r e - a d a p t a t i o n The p h o t o m e t r i c system w h i c h p r o v i d e s a p e r f e c t d i f f u s i n g s u r f a c e f o r t he p r e - a d a p t i n g i l l u m i n a t i o n had y e l l o w e d , so i t was n e c e s s a r y t o r e - p a i n t i t . The method was d e v e l o p e d by the a u t h o r , and i t s d e t a i l s a r e t o be found i n t h e A p p e n d i x . The o r i g i n a l i n s t r u m e n t i s w i r e d t o p r o v i d e a t o t a l o f 200 w a t t s p r e - a d a p t a t i o n e n e r g y , b u t because t h e narrow-band f i l t e r s u s e d f o r p r e -a d a p t a t i o n r e s u l t i n a l a r g e decrement i n i n t e n s i t y compared t o t h e un-f i l t e r e d l i g h t , a t o t a l o f 500 w a t t s was r e q u i r e d . T h i s c a l l e d f o r r e -w i r i n g the s o c k e t s f o r t h e 2 p r e - a d a p t a t i o n b u l b s t o b y p a s s t h e i n s t r u m e n t ' s y 79 own c i r c u i t , and t o i n c l u d e i n s t e a d o f 250 V t r a n s f o r m e r s and a V a r i a c . Two P h i l l i p s p h o t o f l o o d b u l b s . rateS a t 250 w a t t s each i n combina-t i o n w i t h I l f o r d g e l a t i n f i l t e r s #623 + #626 and a v a r i a b l e v o l t a g e s u p p l y t o t he b u l b s were s e t up t o p r o v i d e s e p a r a t e BG + Y p r e - a d a p t a t i o n c o n d i -t i o n s , e q u i v a l e n t i n e v e r y way e x c e p t f o r s p e c t r a l c o m p o s i t i o n . . The BG + Y f i l t e r s were i n c o r p o r a t e d i n t o s e p a r a t e p a i r s o f gog-g l e s t o be worn by t h e s u b j e c t . Then, when t h e 2 p r e - a d a p t a t i o n b u l b s were r u n a t 207.5; V i n c o m b i n a t i o n w i t h t h e BG f i l t e r s t h e p r e - a d a p t a t i o n b r i g h t n e s s was t h e same fc r t h e Y f i l t e r w i t h b u l b s r u n a t 152 V, namely, 80 f t f - j L a m b e r t s . B o t h b u l b s were seasoned by 10% o f t h e i r l i f e t o assume ^ a s t a b l e s p e c t r a l energy d i s t r i b u t i o n o f t h e s o u r c e . F u r t h e r , because t h e y were u n d e r - r u n , t h e i r l i f e and s p e c t r a l s t a b i l i t y were enhanced. P h o t o p i c b r i g h t n e s s e q u i v a l e n c e was d e t e r m i n e d w i t h a P r i t c h a r d photometer and v e r i f i e d w i t h an SEI v i s u a l p hotometer (a n e c e s s a r y check s i n c e t h e r e s p o n s e c u r v e o f the P r i t c h a r d d e p a r t s f r o m i n t h e y e l l o w y p a r t o f the s p e c t r u m ) , t h e l a t t e r by two o b s e r v e r s w i t h n o r m a l c o l o r v i s i o n . V o l t a g e t o t h e b u l b s was m o n i t o r e d by t h e e x p e r i m e n t e r w i t h a v o l t m e t e r a t t a c h e d t o t h e V a r i a c . The r e l a t i v e e nergy d i s t r i b u t i o n s o f each f i l t e r i n c o m b i n a t i o n w i t h t h e b u l b s r u n a t the a p p r o p r i a t e v o l t a g e s were measured by a G a m m a . S c i e n t i f i c s p e c t r o r a d i o m e t e r and a r e d i s p l a y e d i n F i g u r e '1-2.. • <.< 80 T e s t f i e l d The Adaptometer comes w i t h s e v e r a l t e s t p l a t e s t h a t a r e i n t e r p o s e d between the s u b j e c t ' s eyes and a l i g h t s o u r c e w h i c h i s a g a i n , u n d e r - r u n , and i n t h i s c a s e , v o l t a g e - s t a b i l i z e d . These t e s t p l a t e s s e r v e d as h o l d e r s f o r BG(&' Y f i l t e r s t h a t matched the p r e - a d a p t i n g g o g g l e s , as w i l l be e x p l a i n e d . There i s a c o n t r o l f o r t h e w i d t h o f t h e s l i t C t h a t conveys t h e t e s t s o u r c e l i g h t t o t h e t e s t p l a t e . As measured w i t h t h e l u x m e t e r sup-p l i e d w i t h the i n s t r u m e n t , t h e s l i t was s e t t o g i v e 23 l u x a t t h e t e s t p l a t e p o s i t i o n w i t h o u t t h e f i l t e r s . Then f i l t e r s w i t h i d e n t i c a l s p e c t r a l d i s t r i b u t i o n s . ( s e e F i g u r e ;;12) t o t h e p r e - a d a p t i n g g o g g l e s were c o n s t r u c t e d so t h a t the BG •!&•,< Y p h o t o p i c b r i g h t n e s e s w e r e e q u a l when t e s t p a t c h f i l t e r s were.combined w i t h the t e s t s o u r c e a t 23 l u x . T h i s meets t h e e q u a l e n e r g y , e q u a l b r i g h t n e s s c o n d i t i o n s d e p i c t e d i n F i g u r e 1/1 under t h e p h o t o p i c t h r e s h o l d c u r v e . B r i g h t n e s s measurements were made w i t h t h e SEI (and n o t t h e P r i t c h a r d w h i c h f a l t e r s a t t h e l o w e r end of t h e p h o t o p i c r a n g e ) by two c o l o r - n o r m a l o b s e r v e r s , and b o t h f i l t e r b r i g h t n e s s e s were 0.13 f t . - l a m b e r t ' s a t the 23 l u x s e t t i n g . The s p e c t r a l r e l a t i v e e n e r g y c u r v e s were o b t a i n e d w i t h t h e Gamma S c i e n t i f i c s p e c t r o r a d i o m e t e r , and t h e y match t h e a p p r o p r i a t e p r e - a d a p t a t i o n s p e c t r a l r e l a t i v e energy c u r v e s ^ b r i g h t n e s s e s •' i f t h e t e s t p a t c h f i l t e r s a r e i l l u m i n a t e d by.-the p r e - a d a p t i n g b u l b s a t v o l t a g e s a p p r o p r i a t e f o r t h e c o l o r e d g o g g l e mate (See F i g u r e '>%?2\, 81 82 The p r e - a d a p t a t i o n and t e s t c o n d i t i o n s meet p r e c i s e l y the methodo-l o g i c a l r e q u i r e m e n t s d e r i v e d from the p r e v i o u s d i s c u s s i o n . Two n o n - o v e r -l a p p i n g ( n o t i c e t h e s m a l l o v e r l a p i n f i l t e r t r a n s m i s s i o n s ) r e c e p t o r p r o -c e s s e s ( i . e . , a " y e l l o w " and a " b l u e - g r e e n " ) a r e d e s e n s i t i z e d t o t h e same e x t e n t ( i . e . , p r e - a d a p t i n g b r i g h t n e s s e s f o r t h e two a r e t h e same); t h e i r i n c r e a s e i n s e n s i t i v i t y i s measured w i t h t h e same ( s p e c t r a l ) q u a l i t y o f l i g h t t h a t d e - a c t i v a t e d them so t h a t t h r e s h o l d d i f f e r e n c e s between t h e two d u r i n g d a r k a d a p t a t i o n a r e r e f e r r e d t o a common z e r o p o i n t . That i s , t h r e s h o l d v a l u e s , w h i c h a r e w h i t e i n t e n s i t i e s i n c i d e n t on c o l o r e d f i l t e r s , a r e r e a d o f f a l o g s c a l e and i n d i c a t e the r e l a t i v e e f f i c i e n c y o f one c o l o r , ( i n t r o d u c e d w i t h a n e u t r a l d e n s i t y f i l t e r i n c o r p o r a t e d i n t h e i n -s t r u m e n t so as t o p r e s e r v e the s p e c t r a l c o m p o s i t i o n o f t h e t e s t p a t c h e s ) , compared to the o t h e r i n s t i m u l a t i n g t h e i r r e s p e c t i v e r e c e p t o r s . E a r l y t h e i n t e n s i t y r e l a t i o n s r e f l e c t cone p r o c e s s e s , l a t e r ones t h e t r a n s i t i o n f r o m cone t o r o d p r o c e s s e s , and f i n a l ones r o d p r o c e s s e s a l o n e . The e l u s i v e mesopic range i s a no-man's l a n d as f a r as r a t i o n a l i z a t i o n s i n terms o f l u m i n o s i t y c u r v e s a r e c o n c e r n e d , but the r e a d e r i s r e f e r r e d t o Bridgman (1953) f o r a c o n v i n c i n g e x p l a n a t i o n o f why BG t h r e s h o l d s l i e above Y ones e a r l y , t h e n b e l o w them l a t e . F i g u r e 13 i l l u s t r a t e s h i s main p o i n t s as t h e y r e l a t e t o the p r e s e n t methodology. The t e s t p a t c h s i z e (11°) was d e f i n e d by a c i r c u l a r h o l e i n one o f t h e a p e r a t u r e p l a t e s p r o v i d e d w i t h t h e i n s t r u m e n t . I t i s imposed between th e t e s t p l a t e and the s u b j e c t , aid i s moved up t o h i d e t h e . t e s t p l a t e from v i e w d u r i n g p r e - a d a p t a t i o n . 83 "Mure- it> I5ridjman's Of S3) Account of m^ofcc tfrts/ioU htL&ons 84 F i x a t i o n P o i n t The i n s t r u m e n t i s s e t f o r 11° p e r i p h e r a l f i x a t i o n , b u t c e n t r a l f i x a t i o n was d e s i r e d h e r e . The r e d f i x a t i o n l i g h t e n t e r s t h e s p h e r e t h r o u g h a s m a l l h o l e w h i c h was bypa s s e d by i n s e r t i n g a t h i n g l a s s r o d w i t h a r i g h t a n g l e bend i n t o t h e f i x a t i o n p o i n t b u l b h o u s i n g so t h a t l i g h t was conveyed down t o t h e m i d d l e o f t h e t e s t p a t c h . The f r e e end of t h e r o d was c u t o b l i q u e l y so as t o d i s p l a y a s m a l l r e d p o i n t o f l i g h t . When some n e u t r a l d e n s i t y c i n e m o i d was p l a c e d i n t h e f i x a t i o n p o i n t b u l b hous-i n g between t h e b u l b and the g l a s s r o d l e a v i n g the h o u s i n g , a s a t i s f a c t o r y l e v e l o f b r i g h t n e s s f o r t h e f i x a t i o n p o i n t c o u l d be m a i n t a i n e d d u r i n g d a r k a d a p t a t i o n so t h a t the r o d was n e v e r v i s i b l e t o t h e s u b j e c t . T h i s was a c c o m p l i s h e d w i t h t h e r h e o s t a t c o n t r o l t h a t the o r i g i n a l i n s t r u m e n t i s eq u i p p e d w i t h f o r t h e p u r p o s e . A f i x a t i o n p o i n t i s a l m o s t e s s e n t i a l f o r n a i v e = s u b j e c t s s i n c e t h e y have a s t r o n g t e n d e n c y t o t u r n t h e i r gaze p e r i p h e r a l l y so as t o i n -v o l v e t h e more s e n s i t i v e r o d a r e a s , e s p e c i a l l y l a t e r i n d a r k a d a p t a t i o n w i t h BG l i g h t . I n t e n s i t y C o n t r o l o f the T e s t f i e l d .. T h i s i s the most e x t e n s i v e m o d i f i c a t i o n t h a t has been made,,and among o t h e r t h i n g s , i t e f f e c t s an a l t e r a t i o n i n t h e t a s k e x p e c t e d o f t h e s u b j e c t . A more d e t a i l e d a c c o u n t o f t h e t e c h n i c a l changes and t h e r e s u l t -i n g e f f e c t on p s y c h o p h y s i c a l v a r i a b l e s i s t o be found i n L a k o w s k i , S u t h e r -l a n d and G o l d t h w a i t e ( i n p r e s s ) . 85 The u n m o d i f i e d machine has an e x p e r i m e n t e r - o p e r a t e d c o n t r o l t h a t d r i v e s a n e u t r a l d e n s i t y wedge t o change t h e i n t e n s i t y o f t h e f l a s h ; s i -m u l t a n e o u s l y a p i n p r i c k t r a v e l s up o r down i n f r o n t of a p i e c e o f g r a p h paper a t t a c h e d t o a drum t h a t r e v o l v e s , t h i s a l l o w s t h e e x p e r i m e n t e r t o punch a h o l e a t a t h r e s h o l d i n t e n s i t y c o r r e s p o n d i n g t o a s p e c i f i c t i m e i n t h e d a r k . As u s e d h e r e , t h e i n t e n s i t y c o n t r o l i s o p e r a t e d by t h e s u b j e c t and t h e p i n p r i c k has been r e p l a c e d by a p i n t h a t keeps a c o n t i n u o u s r e c o r d o f "appearance" and " d i s a p p e a r a n c e " t h r e s h o l d s . The o r i g i n a l a p p a r a t u s r e -l i e d on a method o f l i m i t s t o o b t a i n a d a r k a d a p t a t i o n c u r v e — t h e i n t e n -s i t y , would be l o w e r e d by t h e e x p e r i m e n t e r f r o m a s u p r a - t h r e s h o l d l e v e l u n t i l the s u b j e c t i n d i c a t e d t h a t t h e f l a s h had d i s a p p e a r e d , t h e n t h e i n -t e n s i t y w o u l d be r a i s e d t o the p o i n t o f j u s t b e i n g seen and s i n g l e p i n p r i c k s would be made a t l e v e l s o f appearance and disappearance.,; "the-dark a d a p t a t i o n c u r v e l y i n g midway between t h e two. The m o d i f i c a t i o n r e s u l t s i n a c u r v e made o f o s c i l l a t i o n s a r o u n d v a l u e s i n d i c a t i n g r a t e o f d a r k a d a p t a t i o n and emphasizes t h e c u r r e n t p r a c -t i c e o f r e g a r d i n g a t h r e s h o l d n o t as ,a p o i n t , b u t as a r e g i o n on an i n -t e n s i t y s c a l e . F i g u r e 14 i s r e p r e s e n t a t i v e of t h e k i n d s o f c u r v e s o b t a i n e d t h i s way. B r i e f l y , the adaptometer i n t e n s i t y c o n t r o l J-shaft was o u t f i t t e d w i t h a v a r i a b l e speed motor whose d r i v e d i r e c t i o n c o u l d be r e v e r s e d w i t h -86 hme. in. MtAa-vk (men.) S~f-otn. laJiourskc) £uHeirlA>n<t, tijjaC ^oUir^ac^e. (cn press) t dots <v~c gamble JrhresAoht- re<&&'nj? 87 a lever operated by the subject. The experimenter i n i t i a l l y set the speed of intensity change i n the up and down directions equal to about 3 log units per min., and this remained essentially unchanged from subject to subject. Although the authors cited above (Lakowski, Sutherland and Goldthwaite) have made only a preliminary study into the relationship be-tween psychophysical dark adaptation variables (e.g. rate of change of i n -tensity and absolute threshold; rate of change of intensity and amplitude of oscillation) involved in this method, some of i t s advantages are ob-vious ." F i r s t , i t removes the experimenter as a source of error. In the standard method he complicated the threshold measurement by contributing ank extra^perception and response. Further, i f he attempted to check a. measurement before he recorded i t , as i s often desirable with c l i n i c a l subjects, thresholds, would be recorded after they had occurred. The new method also provides more, threshold measurements per min. (about 9 at a 3 log units per min. speed) than the old method (3 or 4 per min) and this is a definite advantage i n studying diseased conditions that are li k e l y to involve cone processes or rod-cone interactions, as these events pro-duce rapidly f a l l i n g dark adaptation curves. Finally, provision is made for a record of subject inattention because i t results in a large excur-sion of the pen, incompatible with the level or'-rate ofidark-iadaptation at 88 the time i t o c c u r s . U n l i k e the o l d method, t h i s a l l o w s curves to be smoothed through l apses of a t t e n t i o n tha t occur i n the o l d e r , f a t i g u e d , or e m o t i o n a l l y upset sub jec t who c h a r a c t e r i s t i c a l l y appears i n a c l i n i c a l p o p u l a t i o n . 1 89 v PROCEDURE S i n c e some.of the h y p e r t e n s i v e i n f o r m a t i o n was n o t c o l l e c t e d by t h i s e x p e r i m e n t e r , t h e groups a r e d i v i d e d as f o l l o w s : Normal C o n t r o l s F i r s t t h e y were examined f o r n e a r and f a r a c u i t y w i t h s t a n d a r d eye c h a r t s , and t h e b e s t ( c o r r e c t e d ) a c u i t y , t he s u b j e c t c o u l d a t t a i n was recorded-. A l l subsequent t e s t s were p e r f o r m e d w i t h c o r r e c t i v e l e n s e s i f t h e y were n e c e s s a r y . The I s h i h a r a f o l l o w e d . b y t h e TMC t e s t s f o r c o l o r v i s i o n were a d m i n i s t e r e d b i n o c u l a r l y . The P a n e l D-15 was g i v e n , a g a i n b i n o c u l a r l y , b u t i t s i n t e n d e d u s e was s i m p l y t o f a m i l i a r i z e t h e s u b j e c t w i t h t h e format of t h e more d i f f i c u l t 100-;Hue w h i c h was.then c o m p l e t e d ,\ ( b i n o c u l a r l y ) by him. . O c u l a r H y p e r t e n s i v e s T h i s e x p e r i m e n t e r c o n d u c t e d o n l y t h e d a r k a d a p t a t i o n t e s t s on t h e s e s u b j e c t s s i n c e a l l o t h e r measures had been t a k e n ( m o n o c u l a r l y ) p r e v i o u s l y . N o t i c e t h a t t h e r e i s a d i s c r e p a n c y between t h e c o n t r o l and hy-p e r t e n s i v e p o p u l a t i o n s r e g a r d i n g m o n o c u l a r / b i n o c u l a r c o n d i t i o n s o f a l l t e s t s t h e y t o o k i n common, e x c e p t d a r k a d a p t a t i o n . I t i s conceded t h a t a c l i n i c a l s t u d y s h o u l d b e . c o n d u c t e d m o n o c u l a r l y i n t h e i n t e r e s t s o f p r e c i -s i o n and i n t e r p r e t a b i l i t y . ' T h r e e f a c t o r s e n t e r e d t h e d e c i s i o n t o con d u c t 90 t h i s one (dark adaptation)-, '7 b i n o c u l a r l y : (1) G i l l ob ta ined s i g n i f i c a n t r e s u l t s w i t h the two f i l t e r method a p p l i e d b i n o c u l a r l y , (2) the amount of t ime a s i n g l e subjec t would need to devote to comple t ing a l l aspects of the t e s t s run monocula r ly would have been p r o h i b i t i v e ; (3) t h i s study i s i n one sense a p r e l i m i n a r y one—dif fe rences between c o n t r o l s and c l i n i c a l groups are sought, but a more p r e c i s e ( i . e . monocular), s tudy should await the c o n f i r m a t i o n of d i f f e r e n c e s obta ined i n the most economi-c a l f a sh ion ( i . e . - b i n o c u l a r l y ) . _lathematical t echn iques , as exp la ined l a t e r , have been employed to make normals comparable to c l i n i c a l sub jec t s where theres a monocular/ b i n o c u l a r d i sc repancy between, the two groups. Ocula r hyper t ens ives s t a r t e d the dark adap ta t ion procedure ( w i t h o r wi thou t c o r r e c t i v e l e n s e s , as necessary) immediately upon a r r i v a l to the l a b o r a t o r y . N o r m a l . c o n t r o l s r e f e r r e d by an oph tha lmolog i s t completed a l l the p r e l i m i n a r y t e s t s as set out above before dark adap ta t i on was begun; some normal c o n t r o l s who vo lun tee red a l s o fo l l owed t h i s schedu le , but others re turned on a separate day to complete one or the o ther group of t e s t s ( i . e . ^ c o l o r v i s i o n and a c u i t y , o r dark a d a p t a t i o n ) . Test Procedure f o r Dark A d a p t a t i o n During, the course of the whole t e s t the subjec t i s kept under a reasonably s t andard ized i l l u m i n a t i o n schedule to counterac t the e f f e c t s o f 91 l i g h t adap ta t ion before he entered the l a b o r a t o r y , and to equate the c o n d i t i o n s of changing i l l u m i n a t i o n from subjec t to s u b j e c t . The schedule i s se t down i n F i g u r e 1*5 , and i s approximate ly the one used by G i l l . However, i t i s the w r i t e r ' s o p i n i o n based on expe r i ence , tha t each s t a n d a r d i z a t i o n i s not r e a l l y necessary except i n the i n t e r e s t s of be ing c o n s e r v a t i v e , s i nce th resho lds recorded on a s i n g l e sub jec t from day to day wi thou t any schedule at a l l va ry by about on ly 0.1 l o g u n i t . The subjec t undergoes two separate p re -adap ta t ions and t e s t i n g s d i f f e r i n g o n l y i n the c o l o r of the l i g h t used . When he enters he i s seated a t the adaptometer, the purpose of the experiment i s e x p l a i n e d , he i s a l lowed to ask ques t i ons , and i s g e n e r a l l y made to f e e l at ease i n the. s i t u a t i o n . ' The next f i v e minutes are spent i n the dark w h i l e the experimenter takes him through the t e s t i n g procedure, , and he i s asked to p r a c t i c e i t . The . t ime spent t h i s way depends somewhat on the s u b j e c t ' s a b i l i t y to ca t ch on . 1 B r i e f l y , the i n t e n s i t y i s r a i s e d to w e l l above t h r e s h o l d , the sub-j e c t ' s c o n t r o l l e v e r i s put i n a down p o s i t i o n , and he i s asked to watch the f l a shes get dim. As soon as he misses one of the r e g u l a r l y o c c u r r i n g f l a s h e s , he r a i s e s the l e v e r to i n c r e a s e the i n t e n s i t y u n t i l he can j u s t b a r e l y see a f l a s h , whereupon he lowers the l e v e r , a n d so on . F i v e minutes of p r e - adap t a t i on b e g i n s , then a f t e r 2 minutes of dim room i l l u m i n a t i o n , when the subjec t puts on h i s goggles,•.and 2 minutes of dark ' adap ta t ion , . the apera ture p l a t e i s r a i s e d to cover the t e s t pa t ch 92 FIGURE 15 I l l u m i n a t i o n S c h e d u l e f o r D a r k A d a p t a t i o n T e s t i n g Room I l l u m i n a t i o n D ark A d a p t a t i o n Dim Room I l l u m i n a t i o n Dark A d a p t a t i o n L i g h t A d a p t a t i o n T e s t 3 m i n . 5 min. 2 m i n . 2 m i n . 5 m i n . 13 m i n . B l u e - g r e e n Run Dim Room I l l u m i n a t i o n Dark A d a p t a t i o n L i g h t A d a p t a t i o n T e s t 2 min. 2 min. 5 min. 13 m i n . Y e l l o w Run 93 dur ing the 2 minutes of dark and 5 minutes of l i g h t p r e - a d a p t a t i o n . When the 5 minutes are up, the p r e - a d a p t a t i o n bu lbs are turned o f f . The 11° aperature i s put i n p l a c e , the i n t e n s i t y d r i v e i s s t a r t e d , the sub jec t takes o f f h i s goggles, and gets ready to look f o r the f l a s h . that he w i l l c o n t r o l w i t h h i s l e v e r . Dark adap ta t ion l a s t s f o r 13 m i n -utes du r ing which he i s g i v e n frequent reminders to f i x a t e on . the red l i g h t which i s adjusted o f t en s o . t h a t he r epor t s tha t i t i s j u s t b a r e l y v i s i b l e . . For the second dark adap ta t ion r u n , which was always the y e l l o w , the p reced ing "room i l l u m i n a t i o n " and "5 minutes o f dark a d a p t a t i o n " are e l i m i n a t e d s i n c e i t was the 5 minutes of dark adap ta t ion tha t u n - d i d . - . e f f e c t s of e a r l i e r known ( i . e . , 3 min . ) and unknown amounts of l i g h t adap-t a t i o n the sub jec t had been i n . 94 V I . ANALYSIS OF THE EXPERIMENTAL•RESULTS , S t a t i s t i c a l C o n s i d e r a t i o n s F i g u r e i l l u s t r a t e d t h e k i n d o f raw d a t a g e n e r a t e d by t h e da r k a d a p t a t i o n e x p e r i m e n t . The n e x t s t e p was t o d e c i d e how t o r e c o r d t h r e s h o l d i n t e n s i t y each -minute—-whether t o smooth the c u r v e o b t a i n e d by j o i n i n g t he m i d p o i n t o f each up and down o s c i l l a t i o n ( F i g u r e /1^4 ) o r t o c a r r y out an a n a l y s i s u s i n g t h e . r a w c u r v e s drawn t h r o u g h m i d p o i n t s . The l a t t e r method was cho s e n , p a r t l y i n the b e l i e f t h a t t h e s e s u b j e c t -generated- c u r v e s were more " r e p r e s e n t a t i v e " o f t h e " t r u e t h r e s h o l d " , and t h a t t a m p e r i n g w i t h raw d a t a , as c u r v e - s m o o t h i n g m i g h t be t a k e n a s , would be i n a p p r o p r i a t e . The r i s k i n v o l v e d was t h a t a p o s s i b l e i n c r e a s e i n b e t w e e n - s u b j e c t v a r i a b i l i t y w o u l d mask n o r m a l / c l i n i c a l d i f f e r e n c e s ; t o a c e r t a i n e x t e n t t h e s e f e a r s were r e a l i z e d , as w i l l become a p p a r e n t . How-e v e r , keep i n mind t h a t s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s a r e e n -hanced by a more s u b j e c t i v e c r e d i b i l i t y once t h e d e c i s i o n n o t t o smooth c u r v e s was made: i f " e f f e c t s " a p p e a r , even though t h e i r i n t e r p r e t a t i o n may be d i f f i c u l t t o a r r i v e a t s i n c e p a t t e r n s don't r e a d i l y appear when v a r i a -b i l i t y h i d e s s i g n i f i c a n c e , t h e y w i l l be a l l t h e more n o t e w o r t h y i f t h e y have emerged from the chaos o f h i g h v a r i a b i l i t y . S i n c e t h r e s h o l d v a l u e s weren't always g e n e r a t e d by s u b j e c t s f o r e x a c t m i n u t e s , i t was n e c e s s a r y t o i n t e r p o l a t e t o g e t t h r e s h o l d s a t i n t e -g r a l t i m e s Ci.e.» 1, 2, 3.....13 m i n . ) . Keep i n mind, a l s o , t h a t an 95 a r i t h m e t i c a l s c a l e was imposed on t h e ( s u b j e c t i v e ) l o g i n t e n s i t y s c a l e t o r e a d o f f t h r e s h o l d b r i g h t n e s s ' so t h a t t h e ' e u s u l l mean s t a n d a r d d e v i a t i o n e t c . , c o u l d be c a l c u l a t e d . When the normal d i s t r i b u t i o n c o u l d be assumed t o u n d e r l i e a samp-l i n g d i s t r i b u t i o n (and I have sometimes f o l l o w e d G i l l ' s l e a d i i i making t h e d e c i s i o n ) t - t e s t s were p e r f o r m e d t o a s s e s s t h e s i g n i f i c a n c e o f d i f f e r e n c e s between means. O t h e r w i s e , non-pcarametric i n f e r e n t i a l s t a t i s t i c s have been us ed. The c h o i c e o f t — t e s t s needs j u s t i f i c a t i o n b ecause i t was made w i t h ; some r e s e r v a t i o n s and u l t i m a t e l y because no t r u l y s a t i s f a c t o r y t e c h n i q u e e x i s t e d f o r a n a l y s i n g much o f t h e d a r k a d a p t a t i o n d a t a . T a b l e V I i s a scheme f o r t h e " d e s i g n " o f t h e d a r k a d a p t a t i o n ex-p e r i m e n t . P a r t (a) shows how each m i n u t e ^ i n t h e da r k f o r each s u b j e c t , v a r i o u s l y c a t e g o r i z e d , can r e s u l t i n . c e l l s t h a t have means and s t a n d a r d d e v i a t i o n s . I t would be p o s s i b l e t o a s s e s s the s i g n i f i c a n c e . o f any d i f f e r - , ence we were i n t e r e s t e d i n s i m p l y by d o i n g a t - t e s t r e f e r r e d t o t h e a p p r o -p r i a t e c e l l s . T h i s i s what G i l l has done i n h i s t h e s i s , b u t the p r o c e d u r e i s i l l e g i t i m a t e f o r t h e f o l l o w i n g r e a s o n ( I ' v e f o l l o w e d K i r k , 1968, h e r e ) . O r t h o g o n a l c o m p a r i s o n s between means ( i . e . , t h o s e u s i n g n o n - o v e r -l a p p i n g i n f o r m a t i o n ) can each be t e s t e d a t an *C - l e v e l i n d e p e n d e n t o f one a n o t h e r . N o n - o r t h o g o n a l c o m p a r i s o n s between means o r o r t h o g o n a l com-p a r i s o n s u s i n g a s i n g l e e s t i m a t e o f t h e e r r o r v a r i a n c e c a n ' t be so t e s t e d 96 TfiBLE y i x x \ ) E S l W OUTVIE txPeftvi-VfcUT QL.. /Oct* (cut MypvhteriS't-'w.s ML 1-13 /•-'/3 CL 1 t-\I-I3 JL. QLL 1-iS :B<SJ. y. Sn inn 'I I So . Snti '•5nn Stir* i <tic. etc. 5) J L 5 o- splUpUt design .'_ i 0.i.O,Vi #7* ^ 7A. . . . . . . . #7/J c, C, c, Cz." S:. '. S« Si • 5> 5K, Si Snti 5m Snti sU 5 ^ 1 C h Cfcrs La C°Lev CBlj')) H Ftfei-s io mmoa^/hypertensive a. r-efo-s -to eye (oU^jou^) V rC$e.v-5 io Volon-tcer/clinicaC 97 — t h e more comparisons s c r u t i n i z e d t h e h i g h e r t h e p r o b a b i l i t y o f making a Type I e r r o r - among t h o s e c o m p a r i s o n s : S i n c e many o f t h e i n t e r e s t i n g e f f e c t s i n v o l v e n o n - o r t h o g o n a l com-p a r i s o n s , the r e a s o n a b l e t a c t w o u l d be t o a n a l y z e t h e e x p e r i m e n t as a s p l i t p l o t d e s i g n , P a r f e ( b ) ^ t h e n employ t h e o b t a i n e d e r r o r terms i n an a p o s t e r i o r i -Srcheffe's t e s t t h a t s e t s the e r r o r r a t e e x p e r i m e n t - w i s e . U n f o r t u n a t e l y , t h e v a r i a n c e - c o v a r i a n c e m a t r i x i s n o t homogenous and a u n i v a r i a t e a n a l y s i s i s n ' t a p p r o p r i a t e . S i n c e m u l t i v a r i a t e t e c h n i q u e s w o u l d make t h e i n t e r p r e t a t i o n o f t h e r e s u l t s d i f f i c u l t , Dunn's a p r i o r i t e s t t h a t s e t s t h e e r r o r r a t e a t f o r a l l o r t h o g o n a l + n o n - o r t h o g o n a l c o m p a r i s o n s was t r i e d . Because t h e e r r o r t erm has o n l y a s m a l l number o f degrees o f freedom h e r e , and be c a u s e the l a r g e number of comparisons under c o n s i d e r a t i o n make t h e c r i t i c a l d i f f e r -ence even more d i f f i c u l t t o meet, a l m o s t no co m p a r i s o n s s u r v i v e d as s i g n i -f i c a n t . So we've come f u l l c i r c l e back t o m u l t i p l e t - t e s t s f o r want o f a n y t h i n g b e t t e r . They a r e p r e s e n t e d h e r e w i t h a c a u t i o n n o t t o t a k e s i g -n i f i c a n c e t o o s e r i o u s l y . I t w o u l d , o f c o u r s e , be p o s s i b l e t o make s e t s o f o r t h o g o n a l c o m p a r i s o n s , and e a c h member o f e a c h s e t woul d i n d e e d be s i g n i -f i c a n t o r i n s i g n i f i c a n t a t t h e °C l e v e l s p e c i f i e d . But t h e f i n a l i n t e r -p r e t a t i o n d e v e l o p e d on t h e b a s i s o f s u c k an a n a l y s i s would p r o b a b l y jump a c r o s s o r t h o g o n a l s e t s , and t h e e r r o r r a t e would r i s e a c c o r d i n g l y . 98 Some comment is in o r d e r concerning the role that P e a r s o n ' s r plays in the analysis, since the meaning of the relationship expressed by. a correlation coefficient is necessarily colored by the experimenter's prejudice. I have followed N u n n a l l y (1967) and G a r r e t t (1954) in this discussion. F i r s t , r i s meant to apply to linear relationships in that i t des-cribes that sort of relationship best. D e p a r t u r e s from linearity reduce the magnitude of the correlation, but they don't make i t "wrong"; the large number of variables generated by .this study precluded making -^every relevant scattlBgram, or doing tests for linearity before ir was computed, so that small r ' s may or may not be due to departures from linearity. When i t has come about that a small r disrupts an otherwise interpretable set of data a scatte'rjgram was.constructed to investigate (subjectively) the'$qssibl&-+ri6ajlinearity of the relationship. • A l s o * r ' s have been calculated here when one or both variables • are known.to have non-normal distributions. T h i s procedure is often c r i t i -cized, but i t is a reasonable one i f we bear in mind that such an r no longer estimates a population parameter, rather, i t is an index of a re-lationship for a specific set of measurements, and must be treated as such. The fact that we are no longer doing inferential statistics in such instances shouldn't cause us to ignore'the correlation as long as state-ments relying on i t are. made cautiously. 99 Some r e a d e r s may be s u r p r i s e d t o see t h a t o b v i o u s l y d ichotamous v a r i a b l e s (e.g., sex) o r a r t i f i c i a l l y c a t e g o r i z e d i n f o r m a t i o n ( e . g . y l O P , b l o o d p r e s s u r e ) have been d e a l t w i t h u s i n g r , and n o t one of t h e o t h e r c o r r e l a t i o n c o e f f i c i e n t s . The r e a s o n i s t h a t t h e product-moment c o e f f i -c i e n t i s t h e b a s i c s t a t i s t i c upon w h i c h t h e o t h e r s a r e b a s e d , and f o r t h e same s e t . o f i n f o r m a t i o n t h e y b o t h g i v e t h e same c o e f f i c i e n t as l o n g as t h e u n d e r l y i n g measurement f o r the v a r i a b l e s i s based on.an i n t e r v a l s c a l e ; no s e r i o u s o b j e c t i o n can be r a i s e d a g a i n s t t h e a s s u m p t i o n o f s u c h a s c a l e f o r any v a r i a b l e h e r e . • The c a t e g o r i z a t i o n o f IOP, b l o o d p r e s s u r e , m a c u l a r s e n s i t i v i t y , and d i s c r a t i o s , w h i c h a r e a l l c o n t i n u o u s v a r i a b l e s , needs some e x p l a n a -t i o n . ' The g r o u p i n g s f o l l o w e d c l i n i c a l assessments o f s e v e r i t y , and so a r e r e a l i s t i c f r o m an o p t h a l m o l o g i s t ' s p o i n t o f v i e w i n t h e way t h a t p u r e numbers a r e n ' t , and any s i g n i f i c a n t c o r r e l a t i o n between them and d a r k a d a p t a t i o n v a r i a b l e s g a i n c l i n i c a l i m p o r t a n c e f o r t h a t r e a s o n . F u r t h e r , n o t h i n g was l o s t . b y . f o l l o w i n g t h i s p r o c e d u r e s i n c e c o e f f i c i e n t s c a l c u l a t e d u s i n g c a t e g o r i e s tended t o d i f f e r v e r y l i t t l e f r o m c o e f f i c i e n t s c a l c u l a t e d u s i n g the o r i g i n a l c o n tinuum o f numbers. F i n a l l y , how i s . r t o be i n t e r p r e t e d ? V a r i o u s g u i d e l i n e s come t o mind, and G a r r e t t h a s . d i s c u s s e d some of them. O b v i o u s l y , some c o r r e l a t i o n s w i l l s u r p r i s e us more t h a n o t h e r s (because o f our knowledge about t h e v a r i a b l e s ) and we have t h e c h o i c e o f r e l e g a t i n g them t o i n s t a n c e s o f Type I e r r o r s , o r o f r e t a i n i n g them as s u p e r - i n t e r e s t i n g . And what l e v e l o f 100 s i g n i f i c a n c e do we adhere to? G e n e r a l l y i n t h i s s t u d y - i f p ^ . 0 5 , 30%-50% o f the v a r i a n c e a s soc i a t ed w i t h the other v a r i a b l e w i l l be accounted for, ' i f p ^ . 0 1 , then 50%-90% of the v a r i a n c e w i l l be accounted f o r . The between subjec t v a r i a b i l i t y must be - cons idered a l s o , s i n c e h i g h v a r i -a b i l i t y jwhich i s n ' t uncommon i n t h i s s tudy , can a r t i f i c i a l l y i n f l a t e . r . I n .the face o f a l l . t h i s , arid because the c o r r e l a t i o n m a t r i x f o r the whole s tudy i s so l a r g e , the p o l i c y has been to p l ace more f a i t h i n a pa t te rned set of r ' s t h a n i n a s i n g l e i s o l a t e d , s i g n i f i c a n t r . I s o l a t e d r ' s s i g n i f i c a n t at the .01 l e v e l , tha t account f o r 95% of the v a r i a n c e haven ' t been i g n o r e d , but n e i t h e r have r ' s f i t t i n g i n t o a p a t t e r n of c o r -r e l a t i o n s , a l though some may b e . s i g n i f i c a n t at the .05 l e v e l and account for on ly 36% o f the v a r i a n c e . 101 >B". The P r e s e n t S t u d y as an Independent I n v e s t i g a t i o n F o r p u r p o s e s of o r g a n i z a t i o n t h i s l a r g e d i v i s i o n w i l l t r e a t a l l the i n f o r m a t i o n t h a t was c o l l e c t e d f o r b o t h h y p e r t e n s i v e s and n o r m a l c o n t r o l s w i t h t h e e x c e p t i o n o f t h e l a s t s e c t i o n . 1 The n e x t two l a r g e d i v i s i o n s w i l l d e a l m o s t l y - w i t h d a t a t h a t was a v a i l a b l e f o r t h e h y p e r t e n -s i v e s e x c l u s i v e l y , and t h e y a r e b e s t seen as f i r s t , a f o l l o w - u p s t u d y t o t h e L a k o w s k i , B r y e t t , and Drance p a p e r , and t h e n as an a t t e m p t t o a s s o -c i a t e d a r k a d a p t a t i o n w i t h c l i n i c a l v a r i a b l e s . F i g u r e 16 and TableT) ' JVIT summarize t h e d e s c r i p t i v e s t a -t i s t i c s f o r t h e two p o p u l a t i o n s . The b a s i c d i v i s i o n s a r e between i h y p e r t e n -s i v e s and c o n t r o l s on t h e one hand, and o l d and young age groups on t h e o t h e r . T h i s 2 x 2 c a t e g o r i z a t i o n w i l l s e r v e as t h e b a s i c g r o u p i n g f o r most of t h e r e s t o f the a n a l y s i s . Normal s u b j e c t s were o b t a i n e d p a r t l y f r o m the P s y c h o l o g y Department f a c u l t y a n d . p a r t l y t h r o u g h p e r s o n a l c o n t a c t s ; a few were r e f e r r e d by an o p h t h a l m o l o g i s t . The o n l y p r e - s e l e c t i p n i n v o l v e d as f o r c o n g e n i t a l c o l o r b l i n d n e s s and b e s t c o r r e c t e d a c u i t y . The TMC, I s h i h a r a and 100-Hue s c r e e n e d s u b j e c t s on f i r s t v a r i a b l e , .near" and ;-far a c u i t y c h a r t s d i d so i n t h e second. S i n c e h y p e r t e n s i v e s were a l s o s e l e c t e d on t h e s e two v a r i a b l e s , t h e c l i n i c a l and n o n - c l i n i c a l groups a r e matched i n t h i s r e s p e c t . T a b l e V I I I 103 TABLE V I I D i s t r i b u t i o n o f t h e n o r m a l and H y p e r t e n s i v e P o p u l a t i o n s Young n o r m a l s O l d Normals N Age Range Mean Age Age S.D. Median Age Sex 10 41-56 50.3 4.9 4 d * 8 56-83 67.3 8.3 68 5 0* 31-Young H y p e r t e n s i v e s O l d H y p e r t e n s i v e s N 9 9 Age Range 42-55 61-77 Mean Age 50.3 70.2 Age SID. 4.7 5.7 Median Age 51 70 Sex 1&* 8f. 6 ^ 3 ^ A l l Normals A l l H y p e r t e n s i v e s N 18 19 Age Range 41-83 42-77 Mean Age 57.8 59.7 Age S.D. 10.8 11.4 Median Age 55.5 57 Sex 9 9 8 11 104 TABLE V I I I A c u i t y Comparisons Between' C o n t r o l s and Hypertensives-O.D, + O.S. are Considered Separa te ly C o n t r o l s Near a c u i t y ranges from J l to J3 F a r a c u i t y ranges from 20/20 t o 20/40 A c u i t y No v. o f .Cases' From a ' •'.' ' . ' . - t o t a l of J l 33 36 J3 2 36 20/20 26 36 20/40 2 36 Hyper tens ives Near a c u i t y ranges from J l to J3 Far a c u i t y ranges from 20/15 to 20/40 A c u i t y No. of Cases From a '• ' t o t a l of J l 12 38 . J3 3 38 20/15 4 38 20/40 ;.. 1 38 105 shows t o what e x t e n t the a c u i t y m a t c h i n g was s u c c e s s f u l . No c o n t r o l o r h y p e r t e n s i v e s u b j e c t . w a s j u d g e d t o be a c o n g e n i t a l d i c h r o m a t . The whole p o p u l a t i o n s o f n o r m a l s and h y p e r t e n s i v e s a r e w e l l -matched r e g a r d i n g number-of s u b j e c t s , mean and median age, b u t n o t age ran g e . The m a j o r i t y o f n o r m a l s have J l n e a r a c u i t y and t h e h y p e r t e n s i v e s a r e m o s t l y J 2 ; b o t h p o p u l a t i o n s f a v o r s u b j e c t s w i t h 20/20 a c u i t y . Young n o r m a l s and young h y p e r t e n s i v e s a r e w e l l - m a t c h e d e x c e p t f o r t h e s e x d i s t r i b u t i o n , and t h e d i s c r e p a n c i e s t h a t appear i n c o m p a r i s o n s . o f t o t a l p o p u l a t i o n s ' c a n be seen t o a r i s e from t h e i n c o m p a t i b i l i t y between o l d h y p e r t e n s i v e s and o l d n o r m a l s . F i n a l l y , i n the s p e c i f i c a t i o n o f " h y p e r t e n s i v e " i s i n c l u d e d sub-j e c t s w i t h o p e n a h g l e s , n o r m a l d i s c s , and f u l l v i s u a l . f i e l d s (as measured w i t h s t a t i c p e r i m e t r y ) who have r e p e a t e d l y been found t o have i n t r a o c u l a r p r e s s u r e s above 21 mm. The h i g h e s t r e c o r d e d p r e s s u r e s f o r t h i s group ranged between 30 mm.'and'20 mm. ( t h e s u b j e c t w i t h 20 mm, i n t h e l e f t eye had a maximum o f 22 mm. i n the r i g h t ) ; , w i t h a mean o f 24 mm. A l l o c u l a r h y p e r t e n s i v e s u b j e c t s were chosen f r o m p a t i e n t s a t t e n d i n g a glaucoma c l i n i c . The b a s i c d a r k a d a p t a t i o n d a t a t h a t o r i g i n a t e s f r o m t h e means o f t h r e s h o l d measurements f o r B l u e - g r e e n and y e l l o w p r e - a d a p t a t i o n and t e s t c o n d i t i o n s has been d i v i d e d as f o l l o w s : 106 A. Normals ( s p l i t by Age)  Young O l d C. Normals compared t o h y p e r t e n s i v e s - ( s p l i t by A g e ) Young n o r m a l s O l d n o r m a l s compared t o compared t o young h y p e r t e n s i v e s o l d h y p e r -"" * ' . t e n s i v e s B. H y p e r t e n s i v e s ( s p l i t by Age) >' D. Age D i f f e r e n c e s v ( w i t h i n - n o r m a l s v and h y p e r t e n s i v e s ) Young O l d _ T • '• i • " T T _ — T—. N o r m a l s : young H y p e r t e n s x v e s : compared t o o l d young compared s~ "'' • ' ' ~ - ' . ' ' ' '' t o o l d . T a b l e s I X , A-D, and F i g u r e s 17, A-D, c o r r e s p o n d t o groups A-D above and each t a b l e c o n t a i n s t h e f o l l o w i n g i n f o r m a t i o n where t h e i n f o r m a t i o n i s a p p r o p r i a t e f o r the group: 107 1. " a r e i n i t i a l and f i n a l t h r e s h o l d s f o r a s i n g l e c u r v e (BG o r Y) s i g n i f i c a n t l y d i f f e r e n t ? 2. a r e t h e Y and BG c u r v e s s e p a r a t e d s i g n i f i c a n t l y a t each m i n u t e ? 3. a r e s e p a r a t i o n s between a BG/and a Y c u r v e s i g n i f i c a n t l y d i f -f e r e n t ? 4. do BG and Y c u r v e s d i f f e r r e g a r d i n g t h e i r r a t e s o f change each m i n u t e ? Or do two BG o r two Y c u r v e s d i f f e r i n r a t e s of change when t h i s i s t h e a p p r o p r i a t e comparison? 5. a r e v t h r e s h o l d s each m i n u t e (BG compared t o BG o r Y compared t o Y) s i g n i f i c a n t l y d i f f e r e n t ? 6. does t h r e s h o l d v a r i a b i l i t y change f r o m ^ n u t e ^ t o minute-; w i t h i n one c u r v e o r i s t h r e s h o l d v a r i a b i l i t y f o r two s e p a r a t e c u r v e s s i g n i f i c a n t l y d i f f e r e n t a t any s p e c i f i c m i n ute? 7. a r e ' c r o s s - o v e r t i m e s o r i n t e n s i t i e s s i g n i f i c a n t l y d i f f e r e n t ? F i g u r e s f o l l o w i n g the t a b l e s show mean v a l u e s f o r t h e r e l a t i o n -s h i p s t h a t a r e . b e i n g s c r u t i n i z e d . O n l y s i g n i f i c a n t ( i . e . p__.05) d i f f e r -ences, have been r e p o r t e d i n t h e t a b l e s , and a l l o t h e r d i f f e r e n c e s a r e t o be t a k e n as i n s i g n i f i c a n t . T - t e s t s were c a r r i e d out i n e v e r y c a s e ( o r t - t e s t s f o r matched groups where r e p e a t e d measures were i n v o l v e d ) e x c e p t f o r t h e v a r i a b i l i t y d i f f e r e n c e s , which, were t e s t e d w i t h t h e -Fmax".! r a t i o , and c r o s s - o v e r t i m e s and i n t e n s i t i e s w h i c h , w e r e . i n v e s t i g a t e d w i t h Nemenyi!s n o n - p a r a m e t r i c p r o c e d u r e r f o r non-normal d i s t r i b u t i o n s . C r o s s -108 TABLE Normals . (split By Young Y i n i t i a l threshold is . significantly different from the final. BG i n i t i a l threshold is significantly different from the final. 1 2. BG (Si Y curves are sig-nificantly separated at 10 min. 3. BG (&> Y rates of change are significantly dif-ferent between 6 :§) 7, 8 L&>-9 min. 4. BG and Y rates of change are both significantly different from zero at 13 min. 5. Y threshold variability is significantly differ-ent i f 1 min. and 13 min. are compared. A e) - see text Old 1. Y i n i t i a l threshold is significantly different from the final. BG in i t i a l threshold is significantly different from the filial. 2. BG Y curves are sig-nif icantly separated at 11 min. 3. BG £&) Y rates of change are significantly dif-ferent between 3 t_9 4, 4 <&b5, 5& 6, 6 iSa .7 min. 4. BG rate of change is significantly different from zero at 13 min. 5. Y ;&)BG threshold varia-bility are significantly different at 13 min. 109 TABLE IX B H y p e r t e n s i v e s ( S p l i t by Age) - see t e x t Young O l d 14. Y i n i t i a l t h r e s h o l d i s . s i g n i f f c a n t l y d i f f e r e n t f r om f i n a l BG i n i t i a l t h r e s h o l d i s s i g n i f i c a n t l y d i f f e r e n t f r o m f i n a l BG Y c u r v e s a r e s i g -n i f i c a n t l y s e p a r a t e d a t 12 min. BG '& Y r a t e s o f change . a r e s i g n i f i c a n t l y ^ d i f -f e r e n t be tx^eenr. &4 cand 12&IL»3nmin. U BG r a t e o f change i s s i g n i f i c a n t l y - d i f f e r e n t from z e r o a t 13 min. 1. Y i n i t i a l - t h r e s h o l d i s s i g n i f i c a n t l y d i f f e r e n t f r o m f i l i a l • BG i n i t i a l t h r e s h o l d i s s i g n i f i c a n t l y d i f f e r e n t from f i n a l . 2. BG Y c u r v e s a r e s i g -n i f i c a n t l y sep_axaLted a t 1.&2 min. -3. BG Y r a t e s o f change a r e s i g n i f i c a n t l y d i f -f e r e n t between 1&2 min. BG r a t e o f change i s s i g -n i f i c a n t l y d i f f e r e n t from z e r o a t 13 min. Y r a t e o f change i s s i g -n i f i c a n t l y d i f f e r e n t f rom z e r o a t 13 min. 5. - BG min. 13 v a r i a b i l i t y i s s i g n i f i c a n t l y d i f f e r -e n t f r o m min. 1,2,3,5,6,7' v a r i a b i l i t y BG min. 12 f r o m 1,2,3,5,6 BG min. 11 f r o m 1,2,3,5 BG min. 10 from 1,2,3,5 BG m i n , 8 from 1,2,3, BG min. 9 f r o m 1,2,3, BG min. 7 f r o m 1,2,3, 5. BG. t h r e s h o l d s compared a t 8&L1, o r 9j&ll min. have s i g n i f i c a n t l y d i f f e r e n t v a r i a b i l i t y . 110 TABLE IX C Normals Compared t o H y p e r t e n s i v e s ( s p l i t By Age ) — see T e x t Young no r m a l s v s . Young H y p e r t e n s i v e s 1. Y t h r e s h o l d s a r e s i g n i f i c a n t l y d i f f e r e n t a t 1,2,3,4, m i n . BG t h r e s h o l d s a r e s i g n i f i c a n t l y d i f f e r e n t a t 1,2,3,7,8,9 min. 2. Curve s e p a r a t i o n s a r e s i g n i f i -c a n t l y d i f f e r e n t a t 9;&10 min. 3. Y r a t e s o f change a r e s i g n i f i -c a n t l y d i f f e r e n t between 2&3V 4|&5, 5j£6 min. • 4. (No v a r i a b i l i t y s i g n i f i c a n t ! ) 5. C r o s s o v e r t i m e s a r e s i g n i f i c a n t -l y d i f f e r e n t . O l d Normals v s . O l d H y p e r t e n s i v e s 1. Y t h r e s h o l d s a r e s i g n i f i c a n t l y d i f f e r e n t a t 2 ,5 ,6 ,7 ,9 ,10 ,11, 12,13 min. BG t h r e s h o l d s a r e s i g n i f i c a n t l y d i f f e r e n t a t 1 ,2,3,4,6,7,8,9 10,11 min. 2. Curve s e p a r a t i o n i s s i g n i f i -c a n t l y d i f f e r e n t a t 1,11,12 min. 3. (No r a t e o f change s i g n i f i c a n t ) 4. (No v a r i a b i l i t y s i g n i f i c a n t ) I l l TABLE IX I) Age d i f f e r e n c e s ( w i t h i n n o r m a l s h y p e r t e n s i v e s ) See T e x t Normals ' (Young v s . Old) Hypertensives'.' (Young vs...' Old) Y t h r e s h o l d s a r e s i g n i -f i c a n t l y d i f f e r e n t a t min. 1. BG t h r e s h o l d s a r e s i g n i f i c a n t l y d i f f e r e n t a t 1,3,5,6,7,9,10 min. 2. Curve s e p a r a t i o n i s s i g -n i f i c a n t l y d i f f e r e n t a t 1&2 -.min.' • Curve s e p a r a t i o n i s s i g n i f i -c a n t l y d i f f e r e n t a t 2*4 m i n . Y r a t e s o f change a r e s i g n i f i c a n t l y d i f f e r e n t between 1^2, 2^3, 4^5 min. 3. (No r a t e of change s i g n i f i c a n t ^ : . (No v a r i a b i l i t y s i g n i f i -cant').?' BG t h r e s h o l d v a r i a b i l i t y i s s i g n i f i c a n t l y d i f f e r e n t a t 11, 12, 13 min. Y t h r e s h o l d v a r i a b i l i t y i s s i g n i f i c a n t l y d i f f e r e n t a t 11 min. Irl i'i" i IT 1 • "i p' :i. j j •Hit iiilj Pi pi rl'i :iii li.ii i 12 J: i i ; ; i ; ii i: iii! y • - < 17 fit Tit ^* « . J 6 < t $5 A* TCI ,f-r 'tn % i i ^  ' \- f " • : ' TH 1- i - 5 r y ?:•;: r* J ti v. '1 p n / f\. v i ;.::: i . i • • :3 '.. .4 « | P-? 5 »'•': ' i : i : : • — . i - • if Mil1 Mi ttit 19 .1 V • l . i • | A T i • i • • > ill: a if •S-- -- y N I k — ; • V >n «. t» _-l "1 . \ \ H j ! \ w -:: " 1 •"" \ S." > i • 1 • "  i " m . • • ' « • : ; ;:i'i! •:\\: £ ( 1 tr: : :'-/ •" i . i. " - ! -. : :!: :i--~H— • j Co ^ < \']' . • • • iii; iii: iriT :: ••ii :i:! i !:: L rr; i |k-i - r -' 1 ' ' ;: i j : • | j -i liii 'm rt / n (JO f < «v ;k:: ki' .'tl'.'' i:i: __ |:-:k: s "tv;j ••! j : i i : T . . : ;ii: 1" kk hot '</> ft* ii» mi: f -I f y f-* " * \ iii: i i ! : V r." 1 • i' ;i : St ©•2. >^ <* — - ' *" i." •' i •;ki, T ;i i i i rr:i' :: :: : i ; ' 'iii 1 / Or: ii' 1 / i 1 : . : **<' ii'i" 1 " ' .1.--:^ ?i:« fair W '<!% » s i —-1 J \ i i i ; <Zc. j \ .).. \ i y \ i i : I / \ v / F... v i : ; \ • ^ -a J tl.: \ f iki \ .: •: f : -• i : 1 . \ •ki • • i j'" s • - ' 1 0. 1 i • - ; ; -.j •: < i:i i v f lJ T*T 'ii 0 OX - i i .:': L t iir: .tr.:: :kli •i i'*' :: :< ? 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' —!— " L '• 1 ! >l $4; • ( i j • a \-\ AH i j I VJ •j-*> 11_ • i '•••1 - ; — •v<--n • r ' "T •* r ! j-: . _ : <* t • t - * f • > 7 z f. 5 fs mi fat ft-— > i i • - i — — j r 1 y-r* Will ted tr// 'ft hi, H - r ~ ----- =^ P . — - — - • . • • i • • • 1 • ...i . r" i _ ' j —1~. -i i ~[ - S -— — — -s! \ Off • r i i ^ " 1 N • S s: s ' , ' ' ' r ! ( ft 1 * ™ V-! ^ Q J . •> N — 1 1 :. C '.- w i -1 : ; : ; , r tm''- •' ("til \ i • •-•' I :. it • n • [f] Y f : I: :: :: ( ': ft tut • ;: i' :: j : 1 ——i j 3. _ - j . I | • " j I • 1 i • I 1 i J -fib • UOAJL ; <? •••'*\ V : - --- — J — -j i j . . . 1 . ; I i ; I I . . . . . ] | £ <_ la " t '•' A • r/ j i -1 1 :|: •• • t — [ - j U'G _ C i ; . • 7 I i A A 1 - — -j \ :> ^ . • '• • _ — * . J \ s /" \ \ - ~r» -—— /< • '•*«, i i V S. 0 1 • i ^ - j ! • 1 ' j — i . i . . . . . i 1 • I •• 1 5". :' r ..a / ) / -- - i -| i : : : • i — i j j . . . . . . r. t :::: t Mi 3___ | V- v ... i . n . . . . . . . . . . ad m— \ — -— — \ — j — \ ^ \~r-. * \ V 7 — - - - - - -t- V -v -r a__L_ - f — V • H r_ i : :r.. • -s. • - • • - • .-— ** 1 . — - ! — - '• • -. > r: :. • i / t / 1 <H( • / — i — • • j : ' I 1 ; -1: t ——^  — - j — i i i 4 -j 7 0 112 -4! J £>» • • put i a • - -| i J j ' ' • j _ _ •3 I • — tu ten I \ — \t I I i •• — — - I i ' ' * - -Si i -----f • i • 4> / -j - i 1 [ — i s> -I. — i .: i- - - - 1 -- ~ i — -—+-1 :. i :: C - " -r : ' •;:€•::-:: ) / t / u «»* ^ — - j — i ——~i 'A' i i-1 : _ ... ^ s •4. v : —-— T C ^ i -\ -~~: iTiin. • 5 5 : | TZ sv ; ; | J . r m ; S i 1 —• —'—1 „ „ _ ~-• : _ r < < » • • -: i < • t . . •: f f t J : : « 2 • • • . . . . . . . . . .) :4-: I " : : . ' : j _ j -. 4— - — 4f *< [tit -I i 11 ; ir: i ii.-.-__ — -i i i i | i | • 1 i i i i ! -j-- — f - r -f k VS. 'd AL / V ! . f t - i: : *™i ! i'\ ..|-.. L 1 iiii i -ii): (0.6, ! : -1 i 0 * __ - - — — -i • is r V > OJ \ \ j : V j . il • / \ . j; >1 OH « . . Vi; I j AY s y i • • i \ ; i •• i. :i- : ~ -M . 1. 1 -}— : ; : . I i i i i ' • ;:ii iiii' >: i : i:ii' riii : : ' : 5 ii1: ::.. i»i:i iii/ ' i::( 3 •4t *<? to/I A / "an (*»/_ 'J . - J? Qfei J \ i i. i" • i '3? 0 J \ V • J - / \ I i . .j. . . - . .1.. . 1 „ - \ / \ • : " | ' / T - i 4 : - 1 - A i^ i ^i, iii vi ; i ] r-i- ^ - • - ' - • p>. 1 • s • :! ' : : . X | .55 I : -1'. —v> ' • ii iiii , . , . i:;/ r::: _ i i i 'i ;•; i 1: i.i* r:i. i .I: i : i:: - ?:;i -ii*' e : i ;;'> t.: iii/ J- : S ji i i i 1 <"/* e K-'ll ) / -—r iiii :i'i!5 iii iii iii: iii iii it: ::-if -; ri 'ii-li i-i i iii1 iiii ! | i i • • i . ; ; ! ; z i i. • " I • Iiii : -: i i i!;: ii i i • '-• • • i ] 'ii ; ; : ; iii i i ;;.i i iii: j 1 • i —4 i r 1' ./'//> HP* Wtti T — — -.- ! Jr.. ** ty . „ . . — -| ! — 1~—-I j \ j — I i _ ± 'far <>, UA < t yen Htlt "J — I j — H ! i: - " "1 " 1 i \ i a if 1 j tl *f > u ,— — i •i \ / / \ \ -----J s. • ^ \ : • • \ : \j~ \ \ i • r. \ - j — -1 v i : I.".: I — — 1 j — L_ . ! -:_i <- <• -.. . / / f 1 i 1 i • ."jr. — •-"t j i I • - | ' • - - j — \ ! , . i» far. < 'am 1 — r— \ ! * J j - v\ __}_. ) n -a \\ ---- — > V — - • H—>•» ; .* \ ; « -1 W—Ar j — N - —^ - : i yf • • r 5 < \ -• • / ' / i j - -::7 . . . - . if... : : : i ! r v : f r) f 0 • f , f. l i . : : : : i .' 1 136 over times and i n t e n s i t i e s are d e a l t w i t h i n F i g u r e s 18.and 19. F i g u r e s '1? A-D show ra t e s of change of s e p a r a t i o n fo r the comparisons A - D , . b u t no t e s t s of s i g n i f i c a n c e were performed because of the marked curve i r r e g u l a r i t y . Some'remarks are i n order concerning the o v e r a l l cha rac te r of these r e s u l t s . . The normal p o p u l a t i o n s p l i t by age C T a b l e J X a) serves as. a t e s t of whether we have accomplished what we set out to do w i t h the ex -pe r imen ta l method. C e r t a i n l y , dark adap ta t i on took p l ace s i n c e the y e l l o w and b lue -g reen curves have s i g n i f i c a n t l y d i f f e r e n t f i n a l and i n i -t i a l t h r e sho lds for bo th age groups. That the method succeeded i n demon-s t r a t i n g a s p e c t r a l s e n s i t i v i t y s h i f t i s more d i f f i c u l t to m a i n t a i n be-cause the b lue -g reen ahdj_ y e l l o w curves are not s i g n i f i c a n t l y separated through much o f dark adap t a t i on , whereas the expec t a t i on was tha t they would be separated a t every minute except where they c r o s s . The p r e f e r r e d i n t e r p r e t a t i o n here i s to a t t r i b u t e the genera l l a c k of s i g n i f i c a n c e t o . the h i g h t h r e sho ld v a r i a b i l i t y , because a l though the abso lu t e d i f f e r e n c e s i n t h r e s h o l d compare f avo rab ly w i t h G i l l ' s d a t a , f o r i n s t a n c e , h i s s t a n -d a r d - d e v i a t i o n s about the mean th resho lds are lower i n gene ra l than the p r e s e n t l y ob ta ined ones. I n t u r n , the whole problem i s r e fe r i r ab le to the i n i t i a l d e c i s i o n not to smooth raw d a r k . a d a p t a t i o n curves ; G i l l smoothed each s u b j e c t ' s curve before r e c o r d i n g any t h r e sho ld v a l u e s . 137 Another d i f f i c u l t y encountered a t . t h i s p o i n t i s i n d e f i n i n g a n ^ " p o i n t f o r e i t h e r curve . An abrupt r i s e i n t h r e s h o l d v a r i a b i l i t y , o r a sudden i nc r ea se i n the r a t e of change i s u s u a l l y taken as evidence f o r the replacement of cone processes by rod p rocesses . No such evidence e x i s t s i n t h i s case, so when i n t e r e s t cen te rs around cone processes i t won ' t be p o s s i b l e to s p e c i f y wh ich minutes are the c r i t i c a l ones except t h a t ' t h e y are " e a r l y " ones r a t h e r than " l a t e " ones. No cross—over time or. i n t e n s i t y comparisons were s i g n i f i c a n t ex-cept when young normals were compared to young hyper t ens ives f o r c r o s s -over times . However, i f t imes and i n t e n s i t i e s are p l o t t e d fo r a l l the sub jec t s (F igure 18 ) i t ' s p o s s i b l e to separate the d i seased from the normal c o n d i t i o n at 3.45'log u n i t s on the i n t e n s i t y a x i s and 6. 65 min . on the time a x i s so tha t a l a r g e r p r o p o r t i o n of hyper tens ives than normals f a l l on the h i g h s ide of the d i v i s i o n s . , Age e f f e c t s on the c ros s -ove r measures are l e s s ev ident i n a s c a t t e r diagram (Figure l_j) . By. now i t i s apparent that the remainder of the a n a l y s i s of the r e s u l t s ought to center around trends ( i n the ca sua l sense) r a t h e r than around s i g n i f i c a n c e which may be i n v o l v e d o n l y to s t rengthen l e s s formal evidence f o r an e f f e c t . J u s t i f i c a t i o n for t h i s procedure must be r e f e r r e d to the l a r g e s tandard d e v i a t i o n s accompanying mean t h r e s h o l d i n t e n s i t i e s . The d i s c u s s i o n now centers around f i v e groups of e f f e c t s t ha t can be organized around Tables VIX A - _ , F i g u r e s . _7f A- r j . i . i i i : : . ; : . : : : :: . ;. • • -j . :i : i:'i Pi Pi'iii: ;ii i ^ ^ i i i ' ^ i i i P i i i H i P i " T i : :: iiii ::i: iii1.iiii iii :"FT.i ;ppi :iii iiii :iii iiii ii __ _i: i:: -iii i';* :"-"i: : : ; 1 • -1. i" 1 j ..:: •:•::.•• . i . :,.. i •I- • i J ::: r—^ * W i —_ • i • j . — 1 , Jl 1. i i i i i i 1/ • if t> ' . ?^/p s - ) f :•:•: \- X > f * "py >Mp&4 1 • X i i . • • T. . 3- -.ii 7ft; i . £) :::»•.::: J Hiiiii]" i i - i i i i i i - P - ~t> a—+- yl ! | -I • • • •- ^  I _. i f . Nfh b 4£~t /7Jf>&tl 1 Jf _ — I ! • ..... i i, l; • ^ r ^ ^ ^ i i i T - f f -—-h - «. C7_ :::: .S^ " : : :<» . ; : :i / :ii< ' I % • i H i .:.!', ii .ii: :ii; nr—-.:i : i i i i- _ _ J _ _ _ ] _ ;:: i i . : ::;: ::. SI m it'!: 5} IS time Ltk SJttttt 'ML 2 am. i d . tlLkil^ to 140 1. g e n e r a l c h a r a c t e r i s t i c s o f t h e c u r v e s f o r a l l age and c o n t r o l / h y p e r t e n s i v e p o p u l a t i o n s , 2. t h e e f f e c t o f t h e d i s e a s e c o n d i t i o n ( i ; . e . - o c u l a r h y p e r t e n s i o n ) on d a r k a d a p t a t i o n , 3. the e f f e c t o f age on d a r k a d a p t a t i o n , 4. the i n f l u e n c e o f age on d i s e a s e e f f e c t s , 5. • the i n f l u e n c e o f d i s e a s e on age e f f e c t s l ^ ' . ' . . .. ^4)--and-.»:(-5')jdeal w i t h i n t e r a c t i o n . 1. . G e n e r a l C h a r a c t e r i s t i c s • o f t t h e Curves. T h i s s e c t i o n w i l l f i r s t , d e t e r m i n e t o what e x t e n t t h e e x p e r i m e n t t a l p r o c e d u r e s u c c e s s f u l l y measured p r o c e s s e s i t was meant t o measure, and s e c o n d , d e s c r i b e i n what ways young n o r m a l s u b j e c t s , o l d n o r m a l sub-• j e c t s , young o c u l a r h y p e r t e n s i v e s u b j e c t s , and o l d h y p e r t e n s i v e s u b j e c t s p r o d u c e s i m i l a r d a r k a d a p t a t i o n c u r v e s . R e f e r t o T a b l e s I'X A&B^ and F i g u r e s iVJ,rX'&B. a. t h e b l u e g r e e n t h r e s h o l d curve i n i t i a l l y l i e s above t h e y e l l o w c u r v e , t h e n t h e c u r v e s c r o s s and t h e r e l a t i o n s h i p i s r e v e r s e d . b. d a r k a d a p t a t i o n has t a k e n p l a c e , b u t bluer-green a d a p t a t i o n h a s n ' t been completed Ci'.'e., t h e f i n a l BG r a t e of change i s al w a y s s i g n i f i c a n t l y g r e a t e r t h a n z e r o ) . 141 c. the t o t a l t h r e s h o l d i n t e n s i t y change f o r y e l l o w i s a l w a y s l e s s t h a n the t o t a l i n t e n s i t y change f o r blu e r - g r e e n : B l u e - g r e e n Y e l l o w Young n o r m a l h y p e r t e n s i v e Young n o r m a l h y p e r t e n s i v e 1.80 l o g u n i t s • 2.13 l o g u n i t s .93 l o g u n i t s 1.41 l o g u n i t s O l d 2,14 l o g u n i t s 2.22 l o g u n i t s O l d ' 1.23 l o g u n i t s 1.51 l o g u n i t s d. t h e b l u e - g r e e n t h r e s h o l d r a t e o f change i s g e n e r a l l y h i g h e r t h a n the y e l l o w r a t e o f change, e x c e p t i n i t i a l l y , and t h e d i f f e r e n c e s a r e sometimes s i g n i f i c a n t . e. b l u e - g r e e n and y e l l o w t h r e s h o l d r a t e s of change f o l l o w s i m i l a r c o u r s e s — ^ t h e y a r e h i g h i n i t i a l l y and p l a t e a u a f t e r t h e t h i r d minute^-, f . b l u e - g r e e n t h r e s h o l d v a r i a b i l i t y tends t o l i e above y e l l o w v a r i a b i l i t y . g. c r o s s - o v e r t i m e c o r r e l a t e s p o s i t i v e l y and s i g n i f i c a n t l y w i t h b l u e - g r e e n t h r e s h o l d s f o r most m i n u t e . 2. The e f f e c t o f t h e D i s e a s e C o n d i t i o n H e r e , age groups a r e k e p t s e p a r a t e so t h a t o l d h y p e r t e n s i v e s a r e compared w i t h o l d n o r m a l s , and young h y p e r t e n s i v e s w i t h young n o r m a l s b u t t h e e f f e c t s r e c o r d e d h e r e i g n o r e ' a g e ; R e f e r t o r T a b l e ' I X G aiid'cTigure 17 C. 142 a. t h e normal y e l l o w .curve l i e s below t h e h y p e r t e n s i v e y e l l o w c u r v e a t l e a s t f o r t h e f i r s t 5 m i n u t e s (age i n t e r a c t s h e r e and w i l l be d e a l t w i t h l a t e r ) . b. • the no r m a l BG t h r e s h o l d i n t e n s i t y c u r v e l i e s b elow the BG h y p e r t e n s i v e t h r e s h o l d i n t e n s i t y c u r v e t h r o u g h o u t d a r k a d a p t a t i o n . c. Normals have an e a r l i e r mean c r o s s r o v e r t i m e t h a n h y p e r t e n -s i v e s (5.46 v s . 6.38 and 6.26 v s . 8.87)., b u t o n l y young n o r m a l s and young h y p e r t e n s i v e s d i f f e r s i g n i f i c a n t l y . d. • h y p e r t e n s i v e BG and % i r e s h o l d i n t e n s i t y c u r v e s a l w a y s tra-r> v e r s e a g r e a t e r number o f l o g u n i t s between 1 and 13 -min. (see the box d i a g r a m above i n l , c ) . e. f BG and Y c u r v e s e p a r a t i o n i s al w a y s g r e a t e r f o r n o r m a l s be-r yond 8 min.,- and the d i f f e r e n c e i s sometimes s i g n i f i c a n t . f . - o c u l a r h y p e r t e n s i o n has t h e e f f e c t o f c o l l a p s i n g t he ( s i g ^ -n i f i c a n t ) d i f f e r e n c e s between BG ^Sr-Y r a t e s o f change t h a t a r e f ound among n o r m a l s . • "The E f f e c t - , of Age on Dark A d a p t a t i o n These e f f e c t s e x i s t among n o r m a l s a n d ^ h y p e r t e n s i v e s . R e f e r t o Table^IXtlDband F i g u r e '1'7 D. a.age r a i s e s t he BG t h r e s h o l d t h r o u g h o u t d a r k a d a p t a t i o n , a l t h o u g h t h e e f f e c t i s s i g n i f i c a n t o n l y among h y p e r t e n s i v e s . 143 b. age r a i s e s the e a r l y y e l l o w / t h r e s h o l d . c. • age d e l a y s ( i n s i g n i f i c a n t l y ) t h e mean (& median) c r o s s -o v e r t i m e ( f r o m 5.46 t o 6.26 and from 6.38 t o 8.87, where t h e s e a r e means). d. age i n c r e a s e s the t o t a l t h r e s h o l d change over 13 m i n . f o r b o t h t h e Y and BG c u r v e s ( a g a i n , see t h e d i a g r a m under 1, c abo v e ) . e. age e l i m i n a t e s a 13 m i n . s i g n i f i c a n t Y r a t e o f change (but n o t a s i g n i f i c a n t B G ' r a t e o f change) t h a t e x i s t s among young p o p u l a t i o n s . f . : age i n c r e a s e s e a r l y BG t h r e s h o l d v a r i a b i l i t y and d e c r e a s e s ( s i g n i f i c a n t l y at one p o i n t ) l a t e y e l l o w t h r e s h o l d v a r i a b i l i t y . The I n f l u e n c e o f Age o n - D i s e a s e E f f e c t s • R e f e r t o T a b l e f t l X . , and Figure 1'17 C. a. The-normal y e l l o w t h r e s h o l d c u r v e s e p a r a t e s f r o m t h e h y p e r t e n -s i v e c u r v e a t e v e r y m i n u t e f o r o l d h y p e r t e n s i v e s - compared t o o l d n o r m a l s , whereas i t s e p a r a t e s ( s i g n i f i c a n t l y ) o n l y f o r the f i r s t 4 m i n u t e s f o r the young h y p e r t e n s i v e s compared t o young n o r m a l s ; b. d i f f e r e n c e s between n o r m a l s and h y p e r t e n s i v e a r e i n c r e a s e d t o the p o i n t o f s i g n i f i c a n c e i f we compare t h e o l d p o p u l a t i o n s w i t h the young. 144 c. age i n c r e a s e s t h e d i s c r e p a n c y t h a t e x i s t s between mean cro s s r - o v e r t i m e s f o r n o r m a l s compared t o h y p e r t e n s i v e s ( f r o m .92 t o 1.49). 5. • The. I n f l u e n c e o f D i s e a s e . o n Age E f f e c t s (Refer t o T a b l e IXD, F i g u r e 17D. a. D i s e a s e i n c r e a s e s t h e age d i f f e r e n c e s f o r BG t h r e s h o l d s t o the p o i n t o f s i g n i f i c a n c e . b. ' D i s e a s e p r o d u c e s a m o r e ' c o n s i s t e n t ( a l t h o u g h s m a l l ) i n c r e a s e o f o l d - y e l l o w t h r e s h o l d s over young y e l l o w t h r e s h o l d s . c. A l t h o u g h age i n c r e a s e s the Y and BCt'cBofcalniricrease i n s e n s i t i -v i t y . ( i . e . ; i n c r e a s e s t h e d i f f e r e n c e between f i n a l and i n i t i a l t h r e s h o l d s ) d i s e a s e r e d u c e s t h i s d i f f e r e n c e ( s e e t h e d i a g r a m above under l , c ) . d. D i s e a s e i n f l a t e s t h e mean age d i f f e r e n c e s i n cro s s - r o v e r t i m e s ( f r o m 0.80 t o 2.49). Before, t r y i n g t o say a i y t h i n g g e n e r a l about a l l t h i s i n f o r m a t i o n t h e a n a l y s i s of t h e r e m a i n d e r o f t h e d a t a c o l l e c t e d i n common f o r h y p e r r-t e n s i v e s and n o r m a l s w i l l be ,set down. 1. • C o r r e l a t i o n s Between Age and Dark A d a p t a t i o n  s T h r e s h o l d s ( a l l c o r r e l a t i o n s h e r e a r e p o s i t i v e ) a. s t h e "noPftflal pop i l l a t i o n . ( o l d and'young- s u b j e c t s t o g e t h e r ) . The f i r s t two Y m i n u t e s and the f i r s t 5 -minutes o f t h e BG t h r e s h o l d c u r v e p l u s min. 9 1 and -min. .10 of t h e BG c u r v e c o r r e l a t e s i g n i f i c a n t l y w i t h age, and. a maximum o f o n l y 45% o f t h e v a r i a n c e i n t h r e s h o l d s i s e v e r a c c o u n t e d f o r 145 by age v a r i a n c e . b. t i l e , h y p e r t e n s i v e p o p u l a t i o n , ( o l d and young s u b j e c t s t o g e -g e t h e r ) . BG t h r e s h o l d s from m i n . 1 t o 10 and m i n . 12 a r e s i g n i f i c a n t l y c o r r e l a t e d w i t h age, aid a maximum o f 46% o f t h e t h r e s h o l d v a r i a n c e may be a c c o u n t e d f o r by' age v a r i a n c e . There a r e no s i g n i f i c a n t c o r r e l a t i o n s between y e l l o w t h r e s h o l d s and age. 2. ' C o r r e l a t i o n s Between Sex and D a r k A d a p t a t i o n T h r e s h o l d s There are.none f o r any group. 3. - C o r r e l a t i o n s Between- A c u i t y and Da r k A d a p t a t i o n Young normals^and P o I d h y p e r t e n s i v e s show none, however, t h e o t h e r two. groups d o , and t h i s i n d i c a t e s t h a t t o a c e r t a i n e x t e n t t h e s e l e c -t i o n p r o c e d u r e f o r a c u i t y was.not s u c c e s s f u l s i n c e t h e r e was enough v a r i a -b i l i t y i n a c u i t y f o r s i g n i f i c a n t c o r r e l a t i o n s t o appear. Most c o r r e l a t i o n s f o r t h e young h y p e r t e n s i v e group appear between f a r l e f t eye a c u i t y and d a r k a d a p t a t i o n t h r e s h o l d s , b o t h BG & Y. F o r t h e o l d n o r m a l s m o s t ' c o r r e l a t i o n s a r i s e between l e f t eye f a r a c u i t y and BG & Y t h r e s h o l d s , o r between a c u i t y ( n e a r o r f a r ) d e t e r m i n e d w i t h b o t h eyes, s i m u l t a n e o u s l y and BG Y t h r e s h o l d s . ' T h i s l a s t r e s u l t i s v e r y s u r p r i s i n g s i n c e o n l y t h r e e s u b j e c t s had a b i n o c u l a r a c u i t y d i f f e r e n t f r o m 20/20, and o n l y , t w o d i f f e r e d f r o m J l . Such a s m a l l u n d e r l y i n g r a n g e makes t h e c o r r e l a t i o n s open t o s k e p t i c i s m . N e v e r t h e l e s s , t h e p o s s i b i l i t y o f a c u i t y B e i n g confounded w i t h , o t h e r e f f e c t s s h o u l d be k e p t i n m i n d when r e s u l t s a r e i n t e r p r e t e d . 146 4. Dark A d a p t a t i o n and C o l o r ' V i s i o n a, t h e I s h i h a r a . The d i s t r i b u t i o n o f e r r o r s c o r e s f o r ..tjiese p s e u d p - i s o c h r p m a t i c p l a t e s appears i n F i g u r e 20'. None of the s c o r e d i f f e r e n c e s between n o r m a l c o n t r o l s and h y p e r -t e n s i v e s ( s p l i t by age groups o r n o t ) i s s i g n i f i c a n t by t h e m e d i a n t e s t . T h i s c o n f i r m s the L a k o w s k i , B r y e t t , and Drance f i n d i n g t h a t t h e ' I s h i h a r a d o e s n ' t d i s t i n g u i s h between n o r m a l and h y p e r t e n s i v e s u b j e c t s . Not s u r p r i s i n g l y , : t h e r e a r e no c o r r e l a t i o n s between d a r k a d a p t a -t i o n t h r e s h o l d s (BG or_ Y) and e r r o r s c o r e s f o r t h e p l a t e s ; t h i s c o u l d be due t o t h e s m a l l range o f s c o r e s o b t a i n e d (a n e c e s s a r y r e s u l t o f u s i n g t h e t e s t t o e l i m i n a t e .dichromats f r o m the study).. b. s The 100-Hue. , I f h y p e r t e n s i v e s o r n o r m a l s a r e c o n s i d e r e d as a whole ( i . e . , n o t s p l i t i n t o age g r o u p s ) b o t h BG and Y t h r e s h o l d s c o r r e l a t e a t most m i n u t e s w i t h 100-rHue s c o r e s , and as much as 60% of t h r e s h o l d v a r i a b i l i t y may be a c c o u n t e d f o r t h i s way. Once t h e s e b a s i c groups a r e s p l i t by age, c o r r e l a t i o n i s e l i m i n a t e d i n one or t h e o t h e r age group. Thus, young h y p e r t e n s i v e s and o l d n o r m a l s show s t r o n g a s s o c i a t i o n s between l o s s e s i n c o l o r d i s c r i m i n a t i o n and r i s e s i n t h r e s h o l d f o r b o t h t h e Y and BG c o n d i t i o n s , b u t o l d h y p e r t e n s i v e s and young n o r m a l s do n o t . P o s s i b l e r e a s o n s f o r t h i s phenomenon are.'(I). o l d h y p e r t e n s i v e s (and young normals have s m a l l s c o r e r a n g e s w h i c h a r e r e s p e c t i v e l y 46-180 "and 6<r\L42. (2)' o l d h y p e r t e n s i v e s compared w i t h a l l h y p e r t e n s i v e s o r young no r m a l s compared w i t h a l l n o r m a l s have s m i l e r s t a n d a r d d e v i a t i o n s _ _ | — — f - -Hj-Li _ _ _ | _ 1 .! • : 1 . : : : , : ) : —r-r-• I I 1—" : i i .-few — • • i • I : : 0 foptrttns < — - i 1 1 1 '• i i — i — - i -J •— Ltal <hta£ • • i _ ! — a r •— •* 1  —4 ——ti P - H » - i ' ' p . . : ' -i i — f — HI <*~ -<•———-' • • ;: p. — j — -— | i i — * — * : : : ! . P i -.: . — -— ( — f — x/ : 3 •: —i k-— — i - - - - - -. I- -i 5 .-/ V /1 1. i i r i if — . — - — — H >•——.- -<>— —MS 1- »—-P - p — at,', i i r; ' . • ' :,: -.. P I i — -Cl O ( r ^ i P i P r "TP* -- j-'-j — - • -r——-i i.|prp —T-i.iii rtrr . 1- ' ! ,. :::: ir : • — - T T - ' Jr~—- I! 1 _. !: p ; p . v.:: r.::i_ !; tr -trrt TIP -ii Pi ': I :: I: : i i i P ; ; . 1 l!: 111 . i J 148 a s s o c i a t e d w i t h . 100-Hue s c o r e s o r t h r e s h o l d s , (3) o l d h y p e r t e n s i v e s o r young n o r m a l s show a n o n - l i n e a r r e l a t i o n s h i p between 100-Hue s c o r e s and t h r e s h o l d s . .The second and t h i r d e x p l a n a t i o n s a r e p r o b a b l y t h e c o r r e c t ones; T h e r e r e m a i n s t h e p r o b l e m o f a c e r t a i n i n c o m p a t i b i l i t y between c o r r e l a t i o n s f o r a l l h y p e r t e n s i v e s and c o r r e l a t i o n s f o r a l l n o r m a l s , b e -c a u se as r e p o r t e d above, t h e h y p e r t e n s i v e s were g i v e n t h e c o l o r v i s i o n t e s t m o n o c u l a r l y and so t h e c o r r e l a t i o n s f o r t h i s group a r e computed f o r the r i g h t eye and t h e l e f t eye s e p a r a t e l y , u s i n g one t h r e s h o l d v a l u e f o r b o t h eyes a t each m i n . The n o r m a l s t o o k t h e 100-Hue b i n o c u l a r l y , so t h e r e i s o n l y one s e t o f c o r r e l a t i o n s between t h i s t e s t and d a r k a d a p t a t i o n t h r e s h o l d s . Tt w o u l d be p o s s i b l e t o p o o l t h e O.D. and O.-.S. 100-Hue s c o r e s f o r t h e h y p e r t e n s i v e s , t h e n r e c a l c u l a t e r . However, an i n s p e c t i o n o f r e g r e s s i o n l i n e s u s i n g p o o l e d v s . O.D. o r O.S. s c o r e s showed t h a t t h e c o r r e l a t i o n s w i t h d a r k a d a p t a t i o n t h r e s h o l d s change v e r y l i t t l e , so we can i g n o r e any i n c o m p a t i b i l i t y t h a t a r i s e s from the p e c u l i a r i t y o f t h e d a t a c o l l e c t i o n . F i n a l l y , what can be s a i d about t h e 100-Hue s c o r e d i f f e r e n c e s be-tween n o r m a l s and h y p e r t e n s i v e s i n t h i s s t u d y as compared t o t h e L a k o w s k i , B r y e t t and Drance s t u d y ? T a b l e _ X - i s an a t t e m p t t o d e t e r m i n e i f t h e n i n e t e e n h y p e r t e n s i v e s i n c l u d e d i n t h i s s t u d y , w h i c h c o n s t i t u t e d a s u b s e t o f the p o p u l a t i o n used, i n t h e p r e v i o u s r e s e a r c h (55 s u b j e c t s ) , were r e -p r e s e n t a t i v e o f t h e l a r g e r c l i n i c a l group. T h i s i s r e l e v a n t t o how much TABLE X Comparisons Between t h e P r e s e n t Study and t h e L a k o w s k i , B r y e t t artd Drance Study 100-Hue S c o r e s P r e s e n t S t u d y L a k o w s k i , e t a l . Study P r e s e n t Study L a k o w s k i , e t a l . Study Mean no. ot' u... ..ors> o f e r r o r s 101 50 Med i a n 118 17.8% o f t h e popu-l a t i o n have s c o r e s beyond t h e 9 t h p e r -c e n t i l e f o r V e r r i e s t ' s norms 98 50.3 90. 15.7% o f t h e popu-l a t i o n have s c o r e s o b e r ypndd t h e 9 5 t h p e r -c e n t i l e f o r V e r r i e s t ' s norms Young 95 49 93 Young (under 55) 93 48.8 82 t—1 - O.D. + ).S. P o o l e d - Old Mean no. of e r r o r s 107 53 Median 118 O l d (o v e r 55) 102 51.8 98 -O.D. + O.S. P o o l e d -(The hype r t ens ive p o p u l a t i o n not s p l i t by age) (The h y p e r t e n s i v e p o p u l a t i o n s p l i t by age) 150 we'should expect 100-Hue '.score comparisons between hyper t ens ives and normals to match, across the two"• exper iments . As i s r e a d i l y seen, the sma l l e r hyper tens ive p o p u l a t i o n performed s l i g h t l y worse than the l a r g e r one, and more d i f f e r e n c e i s a t t r i b u t a b l e to the o l d sub jec t s than to the young. T - t e s t s were performed on the present s m a l l e r hyper t ens ive p o p u l a t i o n to f i n d i f mean young or o l d hype r t ens ive scores d i f f e r s i g n i f i c a n t l y from T e r r i e s t ' s age p o p u l a t i o n s . S t r i c t l y , a t—test i s i n a p p r o p r i a t e here because the 100-Hue d i s t r i b u t i o n i s J -shaped, l i k e o ther sensory d i s c r i m i n a t i o n cu rves ; but t - t e s t s were performed f o r the 55 member p o p u l a t i o n , and the same ana lys i s i s undertaken here to make the r e s u l t s compat ib le . Data for age norms was taken from Lakowski (1969, Pa r t I I ) , but some i m p r e c i s i o n was in t roduced because the young norm i s taken from the 50 ' s age group, whereas the age range i n the experiment was 42-57. L i k e -wi se the o l d norm was taken from the, 60 ' s age group, but the range i n the experiment was 61-77. T h i s was necessary because the w r i t e r was not aware of any o ther more app rop r i a t e e s t a b l i s h e d norms. Por the t - t e s t on the' young group the e r r o r w i l l be i n the conse rva t i ve d i r e c t i o n , but i n the l i b e r a l l d i r e c t i o n f o r the o l d group. In a d d i t i o n , s i n c e O.D. and O.S . e r r o r scores were p o o l e d , the df fh ffi ' • r were c a l c u l a t e d u s i n g i n s t e a d of N , where N ; = (1 r ^ ) N , r be ing the c o r r e l a t i o n between'O.D. and O.S . 100 .Hue e r r o r s co re s . ' V e r r i e s t ' s v a l u e s 151 are repor ted fo r b i n o c u l a r t e s t i n g wh ich n e c e s s i t a t e s t h i s adjustment. U n f o r t u n a t e l y , the i nc rease i n v a r i a n c e and decrease i n df e l i m i n a t e d the s i g n i f i c a n t d i f f e r e n c e s between normal popu l a t i ons and the 19-member hyper t ens ive p o p u l a t i o n ; Lakowski et a l . , found young hyper-t e n s ive s from the l a r g e r p o p u l a t i o n s i g n i f i c a n t l y d i f f e r e n t from V e r r i e s t f s normals a t the .05 l e v e l , and o l d hyper t ens ives s i g n i f i c a n t l y d i f f e r e n t beyond the .01 l e v e l . : Dur ing the course of the experiment i t became c l e a r tha t there were d i f f e r e n c e s between the normal v o l u n t e e r subjec ts and the' normal sub^ j e c t s r e f e r r e d by an oph tha lmo log i s t . For i n s t a n c e , the mean score f o r o l d r e f e r r a l s on the lOO^Hue was around 200, and the mean fo r o l d v o l u n t e e r s was under 100. I n f a c t , as F igu re 2/liA.^  shows, Y e l l o w and BG v o l u n t e e r th resho lds are c o n s i s t e n t l y lower than r e f e r r a l th resho lds fo r the o l d e r age group, and the l a r g e m a j o r i t y of the d i f f e r e n c e s are s i g n i f i c a n t . jMuch the same can be s a i d about t h r e sho ld v a r i a b i l i t y , but on ly f i v e y e l l o w times ''show s i g n i f i c a n t d i f f e r e n c e s . A l t h o u g h o n l y a t o t a l o f e igh t sub-j e c t s are i n v o l v e d i n these comparisons, these d i s c r e p a n c i e s s h o u l d n ' t be ignored comple t e ly . Another r a the r s u r p r i s i n g f a c t emerges : i f we compare o l d and young normal -volunteers (N - 4 and N == 91. See F i g u r e 21B . The o l d th re sho lds o f t en l i e below the young ones, and i n the case of the y e l l o w cu rve , f i v e times have s i g n i f i c a n t d i f f e r e n c e s . Threshold " v a r i a b i l i t y a l s o decreases 152 Jriyute zia~ Comparisons between tfolutiteeir and referred noh/vaC Subjects OLD NORMALS T t 5 = " X --4---'r-4 ' 1 ! -• i —\ - - . J . t t -•_.t-_r « i _ i : i t — . i I t i r. SL j H r ^  --f-^-3 ^ - /.! X - -- i --.- j .i... _J i i -1- - --~ ^— ; - 1 — 7— . .! t....... i i • T l ^ _1_ _1_ I > - - 4- - \ I 1- 7~i- ~ 'T. J- ' x j H ^ 4 — 4 TR:,..,. 1 X • i . i .It^&^h) -] . L . X ?. ! , ; i '! f ! i ! 0-7-xi jx^Sx V I ! % 1/ : i npd.lru ft??/ i 53 > ^ * > ' M i r< r/i rre •' r . . . . to*/ I- W JL££ • : 4—' * U'U/ — : i : V I'M : ; : / • • • oi*\ r • :: 1 ! V w .... \ ... , % A f 1+ t - . . : : — - — i -—~T ) m h / - • # , - ; — — -* 1 — 1 i t - : : :! . y.: ; — di : j •4* i -"•"Br?-»':i — > V Of' y - — — i - - - - - - -<«• V i •» , —J M #• '• fm. 16 MM t c i r , •r—• • ;: auitt i k-J C&i'a V >: i ^ ... =»*; n MM ' r i . J •* — T : -: ' : ! : . • ~~~ I" # . i ( V 6 n'r - _: 1 • • a -i: i; i < liiii * i !• / J l ::: (*» / « } \ t 4ji, r ) 1 I. iii : : i ; : — — V i i : t — i . . . . 154 with , age f o r t h i s group. C i t wasn ' t p o s s i b l e to l o o k f o r the same e f f e c t among, r e f e r r e d normals because on ly one young r e f e r r e d sub jec t was ob~ trained) .. Th i s means tha t the age e f f e c t obta ined among a l l normals-^ r e f e r r e d and v o l u n t e e r together—must be due to the v e r y much 'h igher th resho lds f o r r e f e r r e d o l d e r sub jec t s that out-weigh, the t h r e s h o l d l ower -i n g e f f e c t of o l d e r v o l u n t e e r s . L i k e w i s e , the e a r l y i n c r e a s e i n BG v a r i a -b i l i t y that occurs w i t h aging i s a t t r i b u t a b l e to the r e f e r r e d sub jec t s and not the vo lun t ee r s when we cons ide r the normal p o p u l a t i o n . 155 ., C.C ^ Summary-and P r e l i m i n a r y D i s c u s S U o n The amount o f a n a l y s i s c a r r i e d o ut so f a r w a r r e n t s some s o r t o f i n t e r p r e t i v e summary. The most d e s i r a b l e i n t e r p r e t a t i o n w o u l d r e l a t e a l l t h e r e s u l t s t o t h e v i s u a l p r o c e s s e s t h a t g e n e r a t e them, b u t t h i s i s n o t alwa y s p o s s i b l e t o do;' o f t e n we must s e t t l e f o r second b e s t i n t h e f o r m o f d e s c r i b i n g how the r e l a t i o n s h i p s between v a r i a b l e s a f f e c t t h e f o r m o f c u r v e s , c o r r e l a t i o n s ; ; e t c . A t the o u t s e t i t i s p o s s i b l e t o d e s c r i b e i n what ways e v e r y s u b j e c t i s the same, and so i n d i r e c t l y , i n what ways age and o c u l a r h y p e r t e n s i o n have no e f f e c t on d a r k a d a p t a t i o n as measured h e r e . D e p a r t u r e s from t h e f o l l o w i n g c h a r a c t e r i s t i c s o f d a r k a d a p t a t i o n would r e p r e s e n t more s e r i o u s d i s t u r b a n c e s : . 1. (The t o t a l i n c r e a s e i n r e t i n a l s e n s i t i v i t y i s alw a y s g r e a t e r f o r . t h e BG c o n d i t i o n t h a n f o r t h e y e l l o w , and t h e d i f f e r e n c e s a p p r o a c h one l o g u n i t . 2. jThe i n c r e a s e i n s a i s i t i v i t y p e r u n i t t i m e ( i . e . , t h e r a t e o f d a r k a d a p t a t i o n a s r e p r e s e n t e d by the s l o p e o f the c u r v e ) i s g r e a t e r a f t e r t he 1s t m i n . f o r t h e BG c o n d i t i o n . Not o n l y does BG l i g h t become a more e f f i c i e n t s t i m u l u s t h a n Y, b u t i t t a k e s on t h a t a b i l i t y f a s t e r t h a n Y l i g h t i n c r e a s e s i n e f f i c i e n c y . BG •,&) Y r a t e o f change c u r v e s seem t o c r o s s : t h e y a r e i n i t i a l l y e q u a l o r 156 Y i s h i g h e r t h a n BG, b u t o f f e r t h e 1st min. t h e Y curve'! ••I p l a t e a u s a t a l o w e r v a l u e t h a n t h e BG c u r v e . The t e n t a t i v e s u g g e s t i o n h e r e i s t h a t f o r b o t h cone and r o d a d a p t a t i o n , h i g h -e r e f f i c i e n c y o f a s t i m u l u s goes hand—in-hand w i t h a more r a p i d g a i n i n s e n s i t i v i t y f o r t h a t s t i m u l u s . 3. BG t h r e s h o l d v a r i a b i l i t y t e n d s t o be h i g h e r t h a n t h e Y. T h i s goes a l o n g w i t h the h i g h e r BG r a t e o f change, s i n c e h i g h v a r i a b i l i t y i s a s s o c i a t e d ! w i t h t h e i m p r e c i s i o n t h r e s h o l d mea-surements have when s e n s i t i v i t y i s c h a n g i n g r a p i d l y , ' b u t . i t p r o -b a b l y a l s o r e f l e c t s t he o r d e r o f t a s k s - - B G c u r v e s were a l w a y s o b t a i n e d f i r s t . 4. A t t h i s p o i n t i t i s d i f f i c u l t t o s a y much about c r o s s - o v e r ' t i m e . G i l l a s s o c i a t e d e a r l y c r o s s - o v e r t i m e s w i t h h i g h c o l o r d i s c r i m i -n a t i o n l o s s e s as e v i d e n c e d by 100-Hue s c o r e s . But i n t h i s s t u d y no c o r r e l a t i o n s between c r o s s - o v e r t i m e s and e r r o r s c o r e s c o u l d be f o u n d . There a r e , however,, many s i g n i f i c a n t p o s i t i v e c o r r e -l a t i o n s between BG t h r e s h o l d s b o t h e a r l y and l a t e , and c r o s s -o v e r . t i m e . Thus, l o s s e s i n BG s e n s i t i v i t y a r e r e l a t e d t o d e l a y s i n t h e s p e c t r a l s e n s i t i v i t y s h i f t . I i i a d d i t i o n , t h i s s t u d y . d o e s n ' t . c o n f i r m G i l l ' s f i n d i n g t h a t m a x i -mums i n t h r e s h o l d v a r i a b i l i t y (BG & Y t a k e n t o g e t h e r ) . , w h i c h a r e i n t u r n r e l a t e d t o p r o c e s s e s o c c u r r i n g d u r i n g a t r a n s i t i o n between r o d and cone 157 v i s i o n , o c c u r j u s t a f t e r the c r o s s - r o v e r t i m e . However, G i l l d e m o n s t r a t e d t h i s r e l a t i o n s h i p o n l y i n p o p u l a t i o n s younger t h a n the p r e s e n t one. F o r t h e t i m e b e i n g t h e n , we c a n ' t say how cross^-over t i m e i s r e l a t e d t o r o d -cone p r o c e s s e s . We t u r n now t o t h e e f f e c t s . d i s e a s e ( i . e . , o c u l a r h y p e r t e n s i o n ) has on d a r k a d a p t a t i o n ^ h o l d i n g age c o n s t a n t : 1. ' The cone t~ -Yi~&";BG s e n s i t i v i t y i s depressed?/; i n a d d i t i o n , r o d BG s e n s i t i v i t y i s d e p r e s s e d . 2.. Crossr-over t i m e i s d e l a y e d , and i n l i g h t o f what was e x p l a i n e d above, t h i s must be an e f f e c t o f t h e r a i s i n g o f t h e BG t h r e s h o l d c u r v e u n d e r c o n d i t i o n s o f o c u l a r h y p e r t e n s i o n . 3. - O c u l a r h y p e r t e n s i o n i n c r e a s e s t h e t o t a l change i n s e n s i t i v i t y t h a t t a k e s p l a c e d u r i n g t h e 13 min. d a r k a d a p t a t i o n , b a s i c a l l y as a r e s u l t o f i a i s e d i n i t i a l t h r e s h o l d s , and a " c a t c h i n g r - u p " e f f e c t t h a t e x p r e s s e s i t s e l f as a l a r g e r d i s c r e p a n c y between i n i t i a l n o r m a l and h y p e r t e n s i v e t h r e s h o l d s t h a n between f i n a l ones. T h i s i s t r u e f o r Y and BG c o n d i t i o n s . 4.. S i n c e the s e n s i t i v i t y d i f f e r e n c e between BG (&' Y c u r v e s i s re^-' C v V duced f o r o c u l a r h y p e r t e n s i v e s a f t e r ' 8 m i n . , i t i s t e m p t i n g t o c o n c l u d e t h a t accompanying s e n s i t i v i t y r e d u c t i o n i s an adjust^-ment i n s c o t o p i c r e l a t i v e l u m i n o u s e f f i c i e n c e s , , a l t h o u g h s u c h s p e c u l a t i o n must be backed up w i t h s e p a r a t e e v i d e n c e b e c a u s e s u c h an a d j u s t m e n t i s o n l y a s u f f i c i e n t , and n o t a n e c e s s a r y e x p l a n a t i o n of t h e f a c t s . 158 1 ' 5. 7T,he third change hypertensives show i s , again, a drawing toge-ther of BG So Y processes-—namely, rate of change. Differences that are s t a t i s t i ca l ly significant for normals become ins igni -ficant for hypertensives. Some of the effects of age-minimize the ocular hypertensive effects on dark adaptation: 1. i t results in a lowering of the BG sensit ivi ty throughout dark adaptation and in a smaller lowering of Y cone sensi t iv i ty . 2. age delays cross-over|rtime. 3. (It increases the total change in sensi t ivi ty that takes place in 13 rniii. of dark adaptation, again,-with the same "catching-up" effect. The aging eye also undergoes some unique changes Cor l i k e -wise, we might have said that the hypertensive eye undergoes some deteriorations not attributable to senescence—C4) and (5) discussed immediately above): 4. In 13 min. the aged 11° ret inal area under examination has reached, i t s f ina l threshold for yellow l igh t . To be sure, i t i s l i t t l e different from i t s younger counterpart at that time, but the young eye w i l l become even more sensitive after 13 min. 5. - A less easily interpretahle aging effect i s that on v a r i a b i l i t y -age increases early BG threshold va r i ab i l i t y and decreases•late 159 Y v a r i a b i l i t y . These e f f e c t s a r e p r o b a b l y a t t r i b u t a b l e t o t h e t a s k s r e q u i r e d of s u b j e c t s ( r e c a l l t h a t the BG c u r v e was a l w a y s o b t a i n e d f i r s t on each s u b j e c t and i s p r o b a b l y more d i f f i c u l t f o r an o l d e r p e r s o n t h a n a younger o n e ) , o r t o changes i n u n d e r l y i n g r e t i n a l p r o c e s s e s — t h a t i s , Y e v e n t s seem t o be s l o w i n g down f o r an o l d e r compared t o a younger s u b j e c t l a t e i n d a r k a d a p t a t i o n , and t h e l a c k o f p r e c i s i o n i n measurement t h a t r a i s e s v a r i a b i l i t y t o a c e r t a i n l e v e l i n young s u b j e c t s , d o e s n ' t e n t e r - t h e p i c t u r e f o r t h e o l d e r one. Young eyes and o l d eyes don't succumb t o t h e e f f e c t s of o c u l a r 4 h y p e r t e n s i o n to the same e x t e n t — w h e r e a s young h y p e r t e n s i v e eyes can ex-p e c t t o e n j o y r e a s o n a b l y normal 13 m i n u t e Y s e n s i t i v i t y , o l d h y p e r t e n s i v e eyes cannot. L i k e w i s e , o l d h y p e r t e n s i v e s must e x p e c t even h i g h e r BG t h r e s h o l d s t h a n t h e i r n ormal c o u n t e r p a r t s who a l r e a d y have t h r e s h o l d s t h a t a r e s i g n i f i c a n t l y h i g h e r t h a n n o r m a l . I n f a c t , whereas n o r m a l h y p e r t e n -s i v e d i f f e r e n c e s a r e o f t e n i n s i g n i f i c a n t f o r young e y e s , t h e a d d i t i o n o f about t e n y e a r s may i n c r e a s e t h o s e d i f f e r e n c e s , t o t h e p o i n t of s t a t i s t i c a l s i g n i f i c a n c e . Age a l s o i n c r e a s e s t h e d i s c r e p a n c y i n c r o s s - o v e r t i m e s t h a t . e x i s t s between young n o r m a l s and young h y p e r t e n s i v e s . Once a g a i n , t h e e f f e c t s o f d i s e a s e on age m i n i m i z e t h e e f f e c t s o f age on d i s e a s e : h y p e r t e n s i o n m a g n i f i e s l o s s e s i n BG s e n s i t i v i t y t h a t a c -company age and b e g i n s to a f f e c t f i n a l Y s e n s i t i v i t y ; i t i n c r e a s e s c r o s s -o v e r time d i f f e r e n c e s due t o a g i n g . 160 S i n c e r a t e of change o f s e p a r a t i o n p r o v e d t o be of l i t t l e a n a l y t i -c a l v a l u e , i t won't be c o n s i d e r e d f u r t h e r . What do the c o r r e l a t i o n s between age and t h r e s h o l d i n t e n s i t y , add t o t h e o v e r a l l i n t e r p r e t a t i o n ? The.groups o f p r i m a r y , i n t e r e s t h e r e a r e a l l n o r m a l s and a l l h y p e r t e n s i v e s . As was j u s t d e s c r i b e d , t h e BG c u r v e i s a f f e c t e d more by a g e . t h a n i n t h e Y c u r v e , and t h i s i s r e f l e c t e d " i n the r e l a t i v e s c a r c i t y o f c o r r e l a t i o n s between Y t h r e s h o l d s and age compared to c o r r e l a t i o n s between BG t h r e s h o l d s and age. I n f a c t , t h e o n l y c o r r e l a t i o n s f o r y a l l o w o c c u r i n what has been assumed t o be t h e cone s e c -t i o n , whereas c o r r e l a t i o n s f o r - B G o c c u r t h r o u g h o u t t h e w h ole c o u r s e o f d a r k a d a p t a t i o n ; i n a d d i t i o n , age a c c o u n t s f o r o n l y 36% o f y e l l o w t h r e s h o l d v a r i a n c e compared to 46% o f BG v a r i a n c e . However, t h e r e i s o n e . r e l a t i o n s h i p t h a t seems s t r a n g e , and no good e x p l a n a t i o n comes t o mind. That i s ; o n l y n o r m a l s u b j e c t s show Y c u r v e / a g e c o r r e l a t i o n s — h y p e r t e n s i v e s show 1none. I n one r e s p e c t t h i s i s n ' t s u r p r i -s i n g s i n c e t h e o l d y e l l o w cone c u r v e r i s e s s i g n i f i c a n t l y above t h e young one o n l y f o r n o r m a l s . H y p e r t e n s i o n r a i s e s t h e o l d y e l l o w c u r v e above t h e young one more c o n s i s t e n t l y t h r o u g h o u t d a r k k a d a p t a t i o n , , b u t a p p a r e n t l y n o t enough t o i n f l u e n c e t h e c o r r e l a t i o n m a t r i x r e g a r d i n g s i g n i f i c a n c e . The problems a c u i t y may.present as a c o n f o u n d i n g v a r i a b l e w i l l be1 t r e a t e d l a t e r 1 i n t h e f i n a l d i s c u s s i o n . 161 G i l l found a moderate degree of nega t ive c o r r e l a t i o n s between c ros s -ove r t imes and scores on the 100-Hue. The:present study.was unable to conf i rm t h i s a s s o c i a t i o n e i t h e r among hypertensives,-, or normals , but i t Was capable of p r o v i d i n g an a s s o c i a t i o n between c o l o r d i s c r i m i n a t i o n lo s se s and dark adap ta t i on s e n s i t i v i t y l o s s e s . The phenomenon i s some-what unexpected" i n that even rod s e n s i t i v i t y f o r b o t h B G ^ Y c o n d i t i o n s 2 appears to be c o r r e l a t e d ( r can be as h i g h as .37) w i t h measurements of an a b i l i t y g e n e r a l l y a t t r i b u t e d to ebne p rocesses . C o r r e l a t i o n s f o r rod s e c t i o n s o f the curve are g e n e r a l l y sma l l e r than f o r cone s e c t i o n s , But they can r each . a s i g n i f i c a n c e l e v e l of 0.01, n e v e r t h e l e s s . The tempting c o n c l u s i o n here i s t h a t , as tyald m a i n t a i n s , cones p a r t i c i p a t e i n t he .de -t e r m i n a t i o n of what have t r a d i t i o n a l l y Been desc r iBed as .rod t h r e s h o l d s . Such a n o t i o n must Be a i r e d w i t h c a u t i o n , fo r r e c a l l tha t the 100-Hue i s . not normal ly d i s t r i B u t e d and r does not es t imate a p o p u l a t i o n p a r a m e t e r ' i n t h i s case. F i n a l l y , we might mention that a separate l i n e o f evidence has ex^ tended other r e s e a r c h e r s ' f i n d i n g s that c o l o r B l i n d i n d i v i d u a l s show reduced dark adap ta t ion w h i c h can Be s p e c i f i c r ega rd ing wavelength . No suBjec t i n t h i s study was. c o l o r - B l i n d i n the sense of Being a c o n g e n i t a l d ichromat , But there was enough v a r i a t i o n i n c o l o r d i s c r i m i n a t i o n w i t h i n the p o p u l a t i o n f o r c o r r e l a t i o n s w i t h dark, adapta t ion, t h resho lds to appear. Thus, acqu i red c o l o r v i s i o n l o s s e s a re q u i t e as powerful (even among "normal" suB.jects) . as h e r e d i t a r y ones i n t h i s sense-. 162 I t i s a p p r o p r i a t e h e r e t o sunmarize t h e e x t e n t t o w h i c h t h e s m a l l h y p e r t e n s i v e p o p u l a t i o n u n d e r . s t u d y i n t h i s e x p e r i m e n t was r e p r e s e n t a t i v e of t h e l a r g e r one u s e d by L a k o w s k i , B r y e t t and Drance. More r e l e v a n t i n -f o r m a t i o n . w i l l be p r e s e n t e d l a t e r , and so w i l l an i n t e r p r e t i v e summary o f the c o m p a t i b i l i t y between the two s e t s o f e x p e r i m e n t a l r e s u l t s . I n s h o r t , t h e s m a l l e r h y p e r t e n s i v e group r e s e m b l e s *the l a r g e r i n t h a t Cl) t h e I s h i h a r a d o e s n ' t s e p a r a t e e i t h e r f r o m n o r m a l s and C2) p e r f o r ^ -mance on t h e 100-r-Hue f o r t h e s m a l l e r p o p u l a t i o n i s p o o r e r t h a n f o r t h e l a r -g e r p o p u l a t i o n , b u t t h e d i f f e r e n c e s a r e n ' t s i g n i f i c a n t Con the. b a s i s of..a t - r - t e s t , u n f o r t u n a t e l y , because raw d a t a i s .needed t o p e r f o r m n o n - p a r a m e t r i c t e s t s ) The c o n c e r n o v e r d i f f e r e n c e s between r e f e r r e d and' v o l u n t e e r sub-j e c t s i s p r o p e r l y seen as a s i d e i s s u e i n t h i s s tudy., N e v e r t h e l e s s , i t a t t a i n s some i m p o r t a n c e i f we c o n s i d e r t h e uses r e s e a r c h o f t h i s t y p e m i g h t be p u t t o . The o l d e r p a t i e n t who v i s i t s t h e o p t h a l m o l o g i s t a l r e a d y l o o k s more l i k e a p o s s i b l e o c u l a r h y p e r t e n s i v e t h a n one o f h i s c o n t e m p o r a r i e s who do e s n ' t v i s i t h i s o p h t h a l m o l o g i s t , i f we c o n s i d e r d a r k a d a p t a t i o n . ' I t th u s becomes d i f f i c u l t t o d i s t i n g u i s h changes due t o a g i n g and t h o s e due t o d i s e a s e . ' I f d a r k a l a p t a t i o n i s to g a i n i n s t a t u r e as a d i a g n o s t i c t o o l the p r e s e n t s t u d y would have t o be r e p e a t e d u s i n g o n l y t h e r e f e r r e d t y p e o f n o r m a l s u b j e c t . 163 How f a r have we p r o g r e s s e d toward a n s w e r i n g t h e q u e s t i o n s posed i n "The T h e o r e t i c a l Framework"? One o f the most g e n e r a l e f f e c t s sought was a d i s t u r b a n c e i n f o v e a l p r o c e s s e s accompanying t h e v e r y e a r l i e s t changes i n open a n g l e glaucoma. The p r e s e n t s t u d y . h a s c o n f i r m e d t h a t beyond a r e a s o n a b l e d o u b t . 1 A t t h e o u t s e t BG t h r e s h o l d curves" were e x p e c t e d t o undergo more changes due t o a g i n g and d i s e a s e t h a n Y c u r v e s , and t h i s i d e a has been a d e q u a t e l y s u p p o r t e d . But d i s e a s e a f f e c t s both.'cone p r o c e s s e s — - n o t j u s t BG, and h e r e t h e r e s u l t s have gone beyond i n i t i a l e x p e c t a t i o n s . The " e x t r a " changes BG curves' i n c o r p o r a t e appear -mostly i n t h e r o d p o r t i o n s . I n r e g a r d t o a g i n g , i t ' s g e n e r a l l y been shown t h a t f o r c a s e s i n w h i c h v a r i a b i l i t y has been r a i s e d i n o l d e r t h r e s h o l d s , i t has been r a i s e d l e s s f o r y e l l o w l i g h t t h a n f o r BG l i g h t , b u t t h e e f f e c t i s n ' t n e c e s -s a r i l y due to y e l l o w l i g h t b e i n g more i n d i f f e r e n t t h a n BG t o changes i n t h e o c u l a r media s i n c e the o r d e r <j£ p r e s e n t a t i o n o f the BG and Y p r e -a d a p t a t i o n / t e s t c o n d i t i o n s i s confounded as a c a use f o r v a r i a b i l i t y . On the o t h e r hand, v a r i a b i l i t y n e e d n ' t i n c r e a s e a t a l l w i t h age as i s seen i n t h e a n a l y s i s p e r f o r m e d on t h e v o l u n t e e r n o r m a l s u b j e c t s . I n f a c t , t h e s i g n i f i c a n t d e c r e a s e i n v a r i a b i l i t y t h i s group showed w i t h age i s e x a c t l y c o n t r a r y t o the I n i t i a l h y p o t h e s i s . W i t h r e g a r d t o t h e L a k o w s k i , B r y e t t and Drance s t u d y , t h e p r e s e n t r e s e a r c h , c o n f i r m s l o s s of f o y e a l f u n c t i o n i n . h y p e r t e n s i v e s . The-most im-164 portant point here.is that two separate kinds of processes (dark adapta-tion and color vision) show evidence of deterioration in the same area (2° central). • . • 165 , "i). A d d i t i o n a l Comparisons w i t h t h e L a k o w s k i , Bryette.,and Drance Study We have a l r e a d y seen t h a t f o r h y p e r t e n s i v e s , b o t h BG and Y t h r e s h o l d s c o r r e l a t e w i t h 100-^Hue s c o r e s . T h i s s e c t i o n w i l l a t t e m p t t o r e l a t e d a r k - a d a p t a t i o n t o o t h e r c o l o r v i s i o n v a r i a b l e s r e l e v a n t o n l y f o r t h e h y p e r t e n s i v e p o p u l a t i o n . The I s h i h a r a , r e c a l l , c o r r e l a t e d not a t a l l w i t h d a r k ^ - a d a p t a t i o n t h r e s h o l d s ; n e i t h e r do t h e P a n e l D-15 o r t h e D u o r i n e , w h i c h l i k e t h e I s h i h a r a , a r e meant t o d e t e c t d i c h r o m a t s . L a k o w s k i , e t a l . , found i n a d d i t i o n , t h a t t h e s e t h r e e t e s t s d i d n ' t h e l p to d i s t i n g u i s h h y p e r t e n s i v e s ; . . f r o m n o r m a l s . S i n c e t h e anomaloscope i s a more p o w e r f u l t o o l i n t h e s e m a t t e r s , t h a t i s where i n t e r e s t c e n t e r s i n t h i s s e c t i o n . T a b l e s XI and X I I show i n what r e s p e c t the s m a l l e r p o p u l a -t i o n used i n t h i s s t u d y i s r e p r e s e n t a t i v e o f t h e l a r g e r . P a r t o f i t i s a r e p e t i t i o n o f T a b l e X- . The anomaloscope midr-matching p o i n t s a r e measures o f a s u b j e c t s d e v i a t i o n from a modal v a l u e , (here a r b i t r a r i l y s e t a t 5 0 ) , w h i c h i t s e l f i s a r a t i o o f amounts o f two p r i m a r y c o l o r s r e -q u i r e d b y t h e s u b j e c t i n a m i x t u r e t o match a . s t a n d a r d . The p r i m a r i e s and s t a n d a r d s hthere a r e r e d and g r e e n t o make y e l l o w , y e l l o w and b l u e t o make n e u t r a l , g r e e n and b l u e t o make b l u e - g r e e n . H y p e r t e n s i v e s need more g r e e n i n the r e d - g r e e n m i x t u r e t h a n n o r m a l s do t o match t h e y e l l o w , more b l u e t o mat c h t h e n e u t r a l , and more b l u e t o match t h e blue^-green. T a b l e s 166 TABLE X I R e l a t i o n Between t h e H y p e r t e n s i v e P o p u l a t i o n s ; The L a k o w s k i , Bryettv.; & Drance P o p u l a t i o n Compared t o t h e P r e s e n t One Young & O l d S u b j e c t s Combined P o p u l a t i o n D i s t r i b u t i o n . .• • '. • ' .' ' ' 1 ' ' . . v •. • _ • • P r e s e n t Study- L a k o w s k i e t a l . Age Range 42-77 35-82 Sex 8 11 28 27 Mean Age 60T25 62.7 S.D. • • - • 13.6 12.5 N 19 ( s u b j e c t s ) 55 ( s u b j e c t s ) - 100-Hue>Scores (O.D. + O.S. P o o l e d ) Mean 101 98 50 50.3 Median. 118 .. 90 ._ . Anomaloscope M i d - M a t c h i n g P o i n t s . Red-Green Mean 56 55 4.7 4.9 Median 55 55 Y e l l o w - B l u e Mean 56 59 8.2 • 10.5 Median 5 4 56 Gre e n - B l u e Mean 63 71 24.1 15.3 Median 58 64 167 TABLE X I I R e l a t i o n Between the H y p e r t e n s i v e P o p u l a t i o n s : the L a k o w s k i , Bryett/.:. & Drance P o p u l a t i o n Compared t o t h e P r e s e n t One ( i n c o r p o r a t i n g an age s p l i t ) P r e s e n t Study L a k o w s k i , e t a l . Age Range Young • O l d Young ( 5 5 ) O l d ( 55) 42-57 61-77 35-54 55-83 N o . o f eyes 20 18 31 65 o r 71 Sex 1 6 ! ^ : . 40+ 66" 12? 1 3 ' f . l 8 ? 36<^ 3 5 * 100-Hue S c o r e s (O.D. + O.S. P o o l e d ) X '• V  mean 95 107 93 102 49 53 . 48.8 51.8 median 93 118 ... 82 98 Anomaloscope m i d - m a t c h i n g p o i n t s Red Green mean 56.1 54.8 55 55 4.9 4.6 4.5 4.8 median 56 55 54 56 Y e l l o w - B l u e mean 54 60 53 62 6.4 14.5 4.3 11.2 median 53 60 54 60 G r e e n - B l u e mean 58 67 61 76 16.5 16.7 12.3 . 17.2 median 57 75 56 74 168 XT and yXII reveal that the smaller and larger populations dif f e r very l i t t l e , except for the greenV£lue mixture. Although comparisons ' aren' t made in the Tables,- Lakowski, et a l . , also investigated matching ranges for the three mixtures; a large matching ranges whose mid—point we just described indicates that many ratios of the primaries make acceptable matches with the standard. Hypertensives have been found to have larger-than-normal matching ranges especially for the ^ Blueppreen and(yellow—blue mixtures, -" " ' h i With a l l this in mind, what relationships do anomaloscope measure-ments have to dark-adaptation measurements? Before detailing the data, note should be taken of the most striking feature in the pattern: that not only early times and thus cone thresholds are significantly associated with color discrimination, but also, later rod thresholds. This is the same kind of surprise produced before by the correlation of rod thresholds with 100-Hue error scores. Among young subjects, only^Red-Green variables correlate with dark-adaptation thresholds—from 4-12 min. and BG from 7-13 min. Old subjects show this pattern: for Red-Green variables (i.e., mid-matching points j^ tor- matching ranges) .» TPbst Y thresholds correlate" late BG thresholds correlate. for Yellow-hlue variables (as • above) ^.{flost yellow thresholds correlate; late BG thresholds • correlate. 169 f o r G r e e n - B l u e v a r i a b l e s (as above) Y t h r e s h o l d s f r o m 4-13 min. c o r r e l a t e ; l a t e BG t h r e s h o l d s c o r r e l a t e . F o r young and o l d s u b j e c t s combined: f p r Red^green v v a r i a b l e s (as a b o v e ) j Most y e l l o w t h r e s h o l d s c o r r e l a t e . f o r Y e l l o w r B l u e v a r i a b l e s (as above) ^no c o r r e l a t i o n s , f-or Greehr-Blue v a r i a b l e s (as above)., Thost BG t h r e s h o l d s c o r r e r l a t e . ( " C o r r e l a t e " s h o u l d be t a k e n as " c o r r e l a t e a t l e a s t a t t h e .05 l e v e l o f s i g n i f i c a n c e ) . I t w ould be d i f f i c u l t t o a c c o u n t f o r t h e c o r r e l a t i o n p a t t e r n as we move fr o m groups s p l i t by age t o t h e whole h y p e r t e n s i v e p o p u l a t i o n c o n -s i d e r e d t o g e t h e r . The o n l y . i m m e d i a t e i n t e r p r e t a b l e r e l a t i o n s h i p t h e t r e n d s b r i n g t o mind i s t h a t between t h e k i n d o f c o l o r d e f i c i e n c y t h e anomaloscope measures d i a g n o s e d most o f t e n , and t h e p a r t i c u l a r c o l o r e d c o n d i t i o n s o f d a r k - a d a p t a t i o n t h a t showed t h e most c o n s i s t e n t c o r r e l a t i o n s , ^ w i t h t h e s e <-measures. Most o f t e n , h y p e r t e n s i v e s were c a t e g o r i z e d as extreme deutrar-nomalous; r e d u c e d d i s c r i m i n a t i o n i n t h e ' y e l l o w , - w h i c h may. accompany s u c h a d e f e c t (as i n d i c a t e d , f o r i n s t a n c e , by the e n l a r g e d m a t c h i n g r a n g e s f o r t h e Red-Green e q u a t i o n ) seems t o be what t h e d a r k - a d a p t a t i o n i s m e a s u r i n g i n d i r e c t l y . BG r o d c u r v e s c o r r e l a t e d l e s s c o n s i s t e n t l y - a n d t h i s goes a l o n g w i t h the f a c t t h a t Y e l l o w - r B l u e d e f e c t s were l e s s pronounced i n d i a g n o s e s p e r f o r m e d w i t h the anomaloscope. 170 100-Hiie s c o r e s a l s o p o i n t e d t o a r e l a t i o n between d a r k - a d a p t a t i o n and c o l o r d i s c r i m i n a t i o n , b u t i n t h a t c a s e y e l l o w and BG c o r r e l a t e d about e q u a l l y w e l l w i t h t h e s c o r e s . T h i s t e s t most o f t e n d e t e c t e d anomalous t r i c h r o m a t i c d e f e c t s o f t h e t e t a r t a n and t r i t a n t y p e s , where d i s c r i m i n a t i o n i s i m p a i r e d i n t h e r e d - p u r p l e and b l u e - g r e e n . Xt was t h e t r i t a n - t y p e o f d e f e c t t h a t was r e s p o n s i b l e f o r t h e c o r r e l a t i o n s f o r BG curves,, b u t i n a d d i t i o n , d e u t a n - t y p e d e f e c t s must have been s t r o n g enough t o g i v e r i s e t o c o r r e l a t i o n s w i t h y e l l o w t h r e s h o l d s . I n f a c t , t h e d i s t r i b u t i o n of m i d -p o i n t s f o r maximum e r r o r s showed a s l i g h t b u l g e i n t h e y e l l o w . 171 E. D a r k ; ) A d a p r a t i o n and C l i n i c a l V a r i a b l e s T h i s s e c t i o n i s c o n c e r n e d w i t h f o u r more measures made on o c u l a r h y p e r t e n s i v e s e x c l u s i v e l y , and t h e i r r e l a t i o n t o d a r k a d a p t a t i o n t h r e s h o l d s : i n t r a o c u l a r p r e s s u r e , - w h i c h was d i s c u s s e d i n t h e r e v i e w of t h e l i t e r a t u r e , under "Glaucoma: a . G e n e r a l C h a r a c t e r i z a t i o n " ; s y s t o l i c and d i a s t o l i c b l o o d p r e s s u r e ; m a c u l a r s e n s i t i v i t y — t h r e s h o l d s e n s i t i v i t y t o w h i t e l i g h t i n a p o s t i l b s a t t h e f o v e a ; degree of c u p p i n g a t t h e d i s c , w h i c h i s c a t e g o r i z e d i n t o n o r m a l , p a l l o r ^ e n l a r g e d , s a u c e r i z e d and e n l a r g e d d p a l l o r and e n l a r g e d , marked p a t h o l o g i c a l c u p p i n g . As was m entioned b e f o r e , even t h e c o n t i n u o u s v a r i a b l e s ( b l o o d p r e s s u r e , i n t r a o c u l a r p r e s s u r e , and m a c u l a r s e n s i t i v i t y ) : have been b r o k e n i n t o c a t e g o r i e s . In a d d i t i o n , i t has been c a l c u l a t e d f o r r i g h t eyes and l e f t eyes s e p a r a t e l y i n s p i t e of t h e f a c t t h a t d a r k a d a p t a t i o n was measured b i n o c u l a r l y . However, i f c o n t i n u o u s v a r i a b l e s were l e f t t h a t way, o r i f p o o l e d v a l u e s f o r 0..DJ+-0..S were used, t h e o v e r a l l p a t t e r n of s i g n i f i c a n t c o r r e l a t i o n s was seen t o change v e r y l i t t l e , and t h e amount o f a c c o u n t a b l e v a r i a n c e d i d n ' t i n c r e a s e o r d e c r e a s e a p p r e c i a b l y . I n t r a o c u l a r P r e s s u r e H i g h e s t r e c o r d e d p r e s s u r e s among 19 s u b j e c t s r a n g e d from 20 mm, Hg ' t o 30 mm. Hg.. Some i d e a o f how w e l l , I t h e .Lak6wski£et ral..., l f elargerL:p.opulation"was r e p r e s e n t e d by the p r e s e n t s m a l l e r one can be g a i n e d by a c o m p a r i s o n o f the d i s t r i b u t i o n of p r e s s u r e s r e c o r d e d a t t h e t i m e c o l o r v i s i o n t e s t i n g was done. 172 P r e s e n t Study L a k o w s k i , B r y e t t V a n d Drartce Mean 0 ;D. 20.1 19.8 CT 3.1 4.5 •0.;S{ 20.3 20.8 <p 2.6 4.9 S i g n i f i c a n t p o s i t i v e c o r r e l a t i o n s a r i s e Between IOP and BG t h r e s h o l d s from m i n . 5 t o 13, But among o l d h y p e r t e n s i v e s o n l y ; up t o 66% o f t h e v a r i a t i o n i n BG t h r e s h o l d s can Be accounted f o r IOP v a r i a t i o n s . B l o o d P r e s s u r e I f a l l h y p e r t e n s i v e s , o l d and young, a r e c o n s i d e r e d t o g e t h e r , d i a s -t o l i c B l o o d p r e s s u r e i s s i g n i f i c a n t l y a s s o c i a t e d w i t h y e l l o w t h r e s h o l d s , m i n . 5 and 7, B u t o n l y 23% o f t h r e s h o l d v a r i a n c e i s a c c o u n t e d f o r t h i s way, and i t has a n e g a t i v e v a l u e . S y s t o l i c p r e s s u r e s r a n g e d from 108 t o 180, and d i a s t o l i c f rom 68 t o i 100. M a c u l a r S e n s i t i v i t y Among h y p e r t e n s i v e s as a w h o l e , m a c u l a r s e n s i t i v i t y c o r r e l a t e s s i g -n i f i c a n t l y and p o s i t i v e l y w i t h BG t h r e s h o l d s , m i n. 5,6,8,9 ,10^ and can acc o u n t f o r up t o 23% o f the v a r i a n c e . ' Among o l d h y p e r t e n s i v e s , a s i g n i f i -c a n t p o s i t i v e a s s o c i a t i o n e x i s t s a g a i n f o r the BG c u r v e a t .min. 6 t h r o u g h 10, and up to- 77% o f t h r e s h o l d v a r i a n c e may Be a c c o u n t e d f o r . Over a l l h y p e r t e n s i v e s , m a c u l a r s e n s i t i v i t y r anged f r o m 0.79 a p o s t i l B t o 3.2 a p o s t i l B s . 173 C u p p i n g No s i g n i f i c a n t . c o r r e l a t i o n s were o b t a i n e d , b u t c u p p i n g r a n g e d o n l y from " n o r m a l " ; t o " e n l a r g e d " . I t i s d i f f i c u l t t o d e t e r m i n e w h e t h e r r e s t r i c t i o n s ' o u g h t t o be p l a c e d on the i n t e r p r e t a t i o n of t h e c o r r e l a t i o n s b ecause o f t h e p o s s i b l e n o n - m o r m a l i t y o f t h e d i s t r i b u t i o n s f o r IOP, b l o o d p r e s s u r e , and m a c u l a r s e n s i t i v i t y ^ D o i n g so would mean t h a t s p e c u l a t i o n about mechanisms was out of t h e q u e s t i o n . F o r t h e ti m e b e i n g , the d i s c u s s i o n w i l l r e l y on. the f a c t t h a t B e c k e r and S c h a f f e r speak about i n t r a o c u l a r p r e s s u r e s i n a way t h a t i m p l i e s t h a t t h e y a r e ^ n o r m a l l y d i s t r i b u t e d , a t l e a s t among a non-^diseased p o p u l a t i o n . M a c u l a r s e n s i t i v i t y i s an i n t e r e s t i n g v a r i a b l e , b u t r e l a t i v e l y more c a u t i o n w i l l be needed s i n c e t h e w r i t e r i s unaware of the form of i t s d i s t r i b u t i o n . B l o o d p r e s s u r e i s t h e l e a s t s p e c t a c u l a r c l i n i c a l v a r i a b l e f r o m the p o i n t o f v i e w o f d a r k ^ a d a p t a t i o n , b u t a g a i n , i g n o r a n c e r e g a r d i n g i t s d i s t r i b u t i o n n e c e s s i t a t e s a c o n s e r v a t i v e i n t e r s p r e t a t i o n of i t s a s s o c i a t i o n w i t h d a r k ^ - a d a p t a t i o n . We can d i s p o s e o f c u p p i n g e a s i l y , because h y p e r t e n s i v e s by d e f i n i -t i o n had n o r m a l , . o r n e a r - n o r m a l d i s c s , and t h i s p r e - s e l e c t i o n i s r e f l e c t e d i n t h e l a c k o f s i g n i f i c a n t c o r r e l a t i o n s w i t h d a r k - a d a p t a t i o n t h r e s h o l d s . I n t r a o c u l a r p r e s s u r e . a n d b l o o d p r e s s u r e , on t h e o t h e r hand, have r e c e i v e d more n o t o r i e t y i n . t h e glaucoma l i t e r a t u r e b ecause o f t h e i r r o l e ' 174 i n t h e development of the d i s e a s e . I n s o f a r as t h i s s t u d y i m p l i c a t e s a n y t h i n g , i t i m p l i c a t e s b o t h . N o t i c e , however, t h a t s i g n i f i c a n t c o r r e -l a t i o n s a r e n o t t o be t a k e n as i n d i c a t o r s o f cause and e f f e c t , so t h e s e r e s u l t s a r e b e t t e r seen as r e a s o n s f o r d o i n g a s t u d y t h a t m a n i p u l a t e s IOP o r d i a s t o l i c b l o o d p r e s s u r e . t o i n v e s t i g a t e t h e i r e f f e c t s on d a r k a d a p t a t i o n . The r e s u l t s f o r m a c u l a r s e n s i t i v i t y a r e w o r t h y o f emphasis because f o v e a l s e n s i t i v i t y i s n o t c o n s i d e r e d abnormal i n t h e s e s u b j e c t s , a t l e a s t n o t i n the t r a d i t i o n a l sense o f r e p r e s e n t i n g t h e o n s e t o f a " f i e l d d e f e c t " . But we've a l r e a d y w i t n e s s e d two a r e a s o f f o v e a l d y s f u n c t i o n — c o l o r v i s i o n and e a r l y d a r k - a d a p t a t i o n , s o . i t ' s n o t p a r t i c u l a r l y s u r p r i s i n g , a f t e r a l l , t h a t a t h r e s h o l d measurement t a k e n under c o n d i t i o n s o f c o n s t a n t a d a p t a t i o n s h o u l d be a s s o c i a t e d w i t h one t a k e n under c o n d i t i o n s o f dynamic a d a p t a t i o n . The q u e s t i o n a r i s e s whether m a c u l a r s e n s i t i v i t y ought t o be c o n s i d e r e d n o r m a l , a t a l l . A t t h i s p o i n t i t i s sanewhat d i f f i c u l t t o e x p l a i n why t h e BG c u r v e a f t e r 5 min. o f d a r k - a d a p t a t i o n has e x c l u s i v e r i g h t s t o c o r r e l a t i o n s h e r e ; o n l y b l o o d p r e s s u r e d e p a r t s f r o m t h e p a t t e r n . The most d i s t u r b i n g i n -s t a n c e i s m a c u l a r s e n s i t i v i t y ; m a c u l a r v i s i o n i s cone v i s i o n , y e t i t c o r r e -l a t e s w i t h r o d t h r e s h o l d s . T h i s same k i n d o f anomaly:, has d e v e l o p e d o t h e r p l a c e s i n the a n a l y s i s of t h e r e s u l t s , and a comprehensive t r e a t m e n t o f i t f o l l o w s i n t h e n e x t s e c t i o n . 175 DISCUSSION The most i m p o r t a n t c o n c l u s i o n s a r i s i n g f rom t h i s r e s e a r c h may be summarized as f o l l o w s : 1. O c u l a r h y p e r t e n s i o n , c o n t r a r y t o t h e t r a d i t i o n a l v i e w , i s c h a r a c -t e r i z e d by d i s t u r b a n c e s i n c e n t r a l v i s i o n . This s t u d y s u p p o r t s o t h e r r e -s e a r c h on c o l o r v i s i o n i n h y p e r t e n s i v e s - s i n c e i t has d e m o n s t r a t e d d a r k a d a p t a t i o n cone l o s s e s i n b o t h age g r o u p s ; r o d p r o c e s s e s , on t h e o t h e r hand, show d i s r u p t i o n m o s t l y i n o l d e r d i s e a s e d e y e s . M o r e o v e r , t h e s e " e x t r a " r o d changes o c c u r i n t h e y e l l o w c u r v e and so a r e p r o b a b l y n o t due t o y e l l o w i n g o f t h e media o r m a c u l a r p i g m e n t a t i o n changes. 1 2. T h e r e i s r e a s o n t o b e l i e v e , a l s o , t h a t o c u l a r h y p e r t e n s i v e s have more t h a n t h e i r f a i r s h a r e o f media and/or m a c u l a r changes b e c a u s e t h e d i s e a s e i n c r e a s e s BG s e n s i t i v i t y l o s s e s t h a t accompany age i h a c o n t r o l group. I n t h e most g e n e r a l terms, t h e n , o c u l a r h y p e r t e n s i v e s undergo b o t h r e t i n a l and p r e - r e t i n a l changes, and r e t i n a l changes may appear i n t h e c e n t r a l a r e a e a r l y i n t h e c o u r s e o f o p en-angle glaucoma. 3. Age and o c u l a r h y p e r t e n s i o n r e s e m b l e one a n o t h e r b o t h i n t h e i r d i r e c t e f f e c t s on d a r k a d a p t a t i o n t h r e s h o l d s and i n t h e i r i n t e r a c t i o n s w i t h each o t h e r . However, i f c u r v e c h a r a c t e r i s t i c s o t h e r t h a n t h r e s h o l d i n t e n s i t y a r e examined (e.g.,, f i n a l r a t e o f change, v a r i a b i l i t y , t h r e s h o l d d i f f e r e n c e s between BGSf) Y, r a t e o f change d i f f e r e n c e s between BG $ Y) , 176 age and the p a t h o l o g i c a l c o n d i t i o n can be s e p a r a t e d i n t h e i r e f f e c t s on d a r k a d a p t a t i o n . 4. S i n c e d i s e a s e t o some e x t e n t s i m p l y e x a g g e r a t e s age changes as measured h e r e , the q u e s t i o n a r i s e s whether age and d i s e a s e a r e o n l y q u a n t i t a t i v e l y d i f f e r e n t , a t l e a s t f o r the. e f f e c t s t h e y s h a r e i n common. The i d e a i s p r o v o c a t i v e b u t i m p o s s i b l e t o answer a t t h i s t i m e . 5. Age changes o c c u r b o t h i n r o d and cane s e c t i o n s o f t h e c u r v e s , b u t o n l y the BG c o n d i t i o n shows r o d changes. BG cone and rod,,<losses ^ a r e p r o b a b l y due t o p r e - r e t i n a l c h a n g e s ^ Y cone l o s s e s a r e l i k e l y due is t o r e t i n a l changes, but BG cone and r o d l o s s e s a r e n o t n e c e s s a r i l y . R e l a t i o n s h i p o f t h i s S t u d y . t o P r e v i o u s R e s e a r c h G i l l ' s work p r o v i d e d t h e t h e o r e t i c a l s t a r t i n g p o i n t f o r t h i s r e s e a r c h . He found i n a d i a b e t i c p o p u l a t i o n t h a t t h e p r e s e n t t e c h n i q u e was a u s e f u l t o o l i n s o r t i n g o u t d i f f e r e n c e s between n o r m a l and c l i n i c a l e y e s ; he found changes i n t h r e s h o l d l e v e l , v a r i a b i l i t y , and r a t e s o f changes j . u s t h a s s a n l a p p l i c a t i o n o f t h e t e c h n i q u e t o a d i f f e r e n t c l i n i c a l p o p u l a t i o n has done h e r e . O n e . d i f f e r e n c e between t h e two e x p e r i m e n t s , however, o c c u r s i n t h e i m p o r t a n c e t h a t c r o s s - o v e r t i m e had as a v a r i a b l e -d i s t i n g u i s h i n g d i a b e t i c and n o r m a l e y e s < — d i s e a s e h a s t e n e d i t s o c c u r e n c e i n G i l l ' s s t u d y , and i t c o r r e l a t e d w i t h c o l o r d i s c r i m i n a t i o n l o s s e s i n a d d i t i o n , i n h y p e r t e n s i v e s i t tend s t o o c c u r l a t e r ( a l t h o u g h n o t s i g n i f i -c a n t l y f o r b o t h age grou p s ) and c o r r e l a t e s o n l y w i t h BG t h r e s h o l d s . These r e s u l t s a r e r e l a t e d and n o t p a r t i c u l a r l y i n t e r e s t i n g i n t h i s c a s e , s i n c e 177 t h e y r e s u l t s i m p l y f r o m the r i s e i n BG t h r e s h o l d s w h i c h r e t a r d s a c r o s s -o v e r p o i n t . R e g a r d i n g age e f f e c t s , G i l l f o u n d , as h e r e , t h a t age r a i s e s BG t h r e s h o l d s t h r o u g h o u t d a r k a d a p t a t i o n , a l t h o u g h h i s age g r o u p s were younger and the r i s e showed l e s s c o n s i s t e n c y . U n l i k e t h e p r e s e n t r e s u l t s , o l d y e l l o w c u r v e s showed l o s s e s i n s e n s i t i v i t y t h r o u g h o u t d a r k a d a p t a t i o n , and n o t j u s t i n the f i r s t few minutes;. U n l i k e what he f o u n d under d i s e a s e e f f e c t s , age r e t a r d e d c r o s s - o v e r t i m e , w h i c h c o r r e s p o n d s w i t h t h e p r e s e n t f i n d i n g s . P o s s i b l y ; , the d i f f e r e n c e s between t h e two s t u d i e s can be a t t r i b u t e d t o t h e s m a l l e r age r a n g e s G i l l used i n each group ( i . e . , 10 y e a r s ) o r t o L the d i f f e r e n c e s i n r e a l ages s a m p l e d - - t h a t i s , he i n v e s t i g a t e d c u r v e s f r o m s u b j e c t s aged 15-50, and t h i s work used s u b j e c t s f r o m 41-83. The l i t e r a t u r e on age and d a r k a d a p t a t i o n i s i n agreement t h a t r o d t h r e s h o l d s i n c r e a s e w i t h age f r o m the. m i d d l e t e e n s on.' The r e s u l t s o f t h i s work c o n f i r m t h i s f o r o l d e r age groups and b l u e - g r e e n l i g h t , b u t n o t f o r y e l l o w , and a l l o w s t h e t e n t a t i v e c o n c l u s i o n t o be drawn t h a t t h e e f -f e c t i s due t o media y e l l o w i n g . Cone t h r e s h o l d s a l s o show l o s s e s i n s e n -s i t i v i t y w i t h age a c c o r d i n g t o t h e l i t e r a t u r e , and t h i s has been c o n f i r m e d h e r e f o r b o t h Y and BG c o n d i t i o n s ; a t l e a s t some l o s s e s a r e o f r e t i n a l o r i g i n i n t h i s c a s e . On the o t h e r hand, the p r e s e n t r e s u l t s a r e u n a b l e t o c o n f i r m o c c a s i o n a l r e p o r t s o f a d e c r e a s e i n r o d o r cone r a t e s o f change, o r o f a 178 r i s e i s t h r e s h o l d v a r i a b i l i t y w i t h age. T u r n i n g now t o the glaucoma/dark a d a p t a t i o n l i t e r a t u r e , i t i s a p p a r e n t t h a t much d i s a g r e e m e n t e x i s t s o v e r whether e a r l y open a n g l e glaucoma c h a r a c t e r i s t i c a l l y shows e l e v a t e d dark'-~adaptation t h r e s h o l d s , a l t h o u g h most r e s e a r c h e r s r e p o r t t h a t " e s t a b l i s h e d " glaucoma does. A p a r t f r o m the p roblems caused by i n c o m p a t i b l e d e f i n i t i o n s o f i n i t i a l glaucoma, t h e p o i n t may be made t h a t age d i f f e r e n c e s a c r o s s e x p e r i m e n t s c o u l d v e r y l i k e l y a c c o u n t f o r some o f t h e d i s a g r e e m e n t , s i n c e o l d h y p e r -t e n s i v e s , f o r i n s t a n c e , show more changes compared t o o l d n o r m a l s . N o t i c e a l s o i n T a b l e I V t h a t sometimes ^ s u s p e c t s " o r " i n i t i a l glaucoma" c u r v e s a r e r e p o r t e d t o l i e between n o r m a l and " e s t a b l i s h e d g l a u -coma" c u r v e s . A s m a l l p r e l i m i n a r y s t u d y u s i n g t h e t w o - f i l t e r method has p r o d u c e d s i m i l a r r e s u l t s . Dark A d a p t a t i o n C u r v e s i n ; a S m a l l Group o f Glaucomatous Eyes . I t i s i m p o r t a n t t o d e m o n s t r a t e d a r k - a d a p t a t i o n l o s s e s i n f u l l glaucoma s i m i l a r t o t h o s e found i n h y p e r t e n s i v e s i n o r d e r t o e l i m i n a t e the p o s s i b i l i t y t h a t the d y s f u n c t i o n f o u n d i n h y p e r t e n s i v e s i s n o t a s s o -c i a t e d w i t h t h e d i s e a s e p r o c e s s e s t h a t r e s u l t i n f i e l d changes, d i s c changes, e t c . A l o n g i t u d i n a l s t u d y would be t h e method o f c h o i c e , b u t t i m e d i d n ' t p e r m i t one. However, a c r o s s - s e c t i o n a l s t u d y was f e a s i b l e u s i n g a group o f f i v e s u b j e c t s aged 70-76 y e a r s . The most s e r i o u s o b s t a c l e t o a s t u d y of t h i s s o r t i a p u p i l . d i a m e t e r , b ecause a l l f i v e p a t i e n t s were u n d e r g o i n g t r e a t m e n t w i t h a m i o t i c , whereas 179 h y p e r t e n s i v e s and n o r m a l s were t e s t e d w i t h a n a t u r a l p u p i l . Glaucomatous eyes were d i a l a t e d , t h e r e f o r e , w i t h N e o s y n e p h e r i n e and a r e c o r d was k e p t o f t h e i r p u p i l d i a m e t e r s j u s t b e f o r e t h e BG r u n , j u s t b e f o r e t h e Y r u n , and i m m e d i a t e l y a f t e r t h e Y r u n . S i n c e t h e room i l l u m i n a t i o n and d a r k -a d a p t a t i o n - l i g h t a d a p t a t i o n s c h e d u l e s were s t a n d a r d i z e d , glaucomas c o u l d be s e l e c t e d by c o m p a r i s o n w i t h e q u i v a l e n t l y aged h y p e r t e n s i v e s whose p u p i l s were measured i n t h e same way. The s e l e c t i o n method i s c r u d e i n t h a t p u p i l changes d u r i n g d a r k and l i g h t a d a p t a t i o n f i g u r e as unknowns, but i t p r o v i d e d a t l e a s t a r o u g h s e l e c t i o n p r o c e d u r e so t h a t t h e s o u g h t -a f t e r l o s s e s i n s e n s i t i v i t y could be i n v e s t i g a t e d i n a p r e l i m i n a r y way. P u p i l s were measured s i m p l y by h o l d i n g a s c a l e o f b l a c k c i r c l e s up t o t h e eyes o f t h e s u b j e c t i n a p l a n e a p p r o x i m a t e l y e q u a l t o t h e p l a n e o f t h e p u p i l . T h i s way, f i v e s u b j e c t s , a l l o f whom f e l l i n t h e second age group were s e l e c t e d on t h e b a s i s o f com p a r i s o n s w i t h n o n - m e d i c a t e d , a g e - c o u n t e r p a r t s . T h e i r i n i t i a l p u p i l measurements r a n g e d , from 2 mm,to 3.5mm., the measurements made b e f o r e t h e Y r u n ranged from 2 mm. t o 4 mm., and t h e f i n a l r a n g e d from 2.5 mm. to. 3.5 mm; a l l r a n g e s a r e w i t h i n 0.5 mm. of h y p e r t e n s i v e r a n g e s . R e f e r t o F i g u r e 22 , b u t keep i n mind t h a t t h e s e n s i t i v i t y l o s s e s glaucomas show w i t h i n a c e n t r a l 11° may be s l i g h t l y i n f l a t e d b e -cause t h e i r ages f e l l i n t h e upper end of n o r m a l and h y p e r t e n s i v e r a n g e s . No glaucomatous - eye had e v i d e n c e o f a scotoma w i t h i n t he 11° t e s t a r e a a t the time d a r k - a d a p t a t i o n c u r v e s were o b t a i n e d , y e t t h e y h a v e ) t h r e s h o l d r - 4 ;:-:r! 80 i i ; : Wl WW'; WWW: — 1 •fact,* Hit y* r-m mtww'- Cfe i • • - —'• P ^ .. tft *i i m ""• rr t U h le'sW • L fair . :i . .,. j •••fit tet. 7°. . s • i — V ,. yj 1 i —i - — • < — .. j" S — 3 - r x r WWiVW : :,:a ::;4 I'WWW WW'. •ww. it- ii /W/-7-: : i. \ i ' i -1 j 1 • 1 \ s : ': I ••• • , [ j ^ ! :. • « * • >_.: • ; : ' , • • • • | . :• .f : WW•%WWW,X www. ww i ' . : : —1___4—.-WW . . T . . , . , : ; !:'-. :::: — , _j :W'rVW T . P : i : .: ::rj t; ; ....... -p 'WW W\\ WJW[rJ • 'I- ;. ! Wli,i\W •I-: www •. 181 v a l u e s t h a t f a l l m o s t l y above the mean h y p e r t e n s i v e v a l u e s . Dark-*-Adaptation and C o l o r V i s i o n The s u g g e s t i o n was made e a r l i e r on t h e b a s i s o f s i g n i f i c a n t c o r r e -l a t i o n s between 100-Hue, s c o r e s , anomaloscope measures and l a t e d a r k adap-t a t i o n t h r e s h o l d s , - t h a t cones may p a r t i c i p a t e i n what a r e u s u a l l y t a k e n t o be r o d t h r e s h o l d s . The a s s e r t i o n r e q u i r e s q u a l i f i c a t i o n : W i t h the s t a t i s t i c a l a n a l y s e s p e r f o r m e d i t i s p o s s i b l e t h a t t h e a s s o c i a t i o n between c o l o r d i s c r i m i n a t i o n and cone t h r e s h o l d s on t h e one hand, and cone t h r e s h o l d s and r o d t h r e s h o l d s on the o t h e r hand c o u l d a c -count f o r t h e a s s o c i a t i o n between r o d t h r e s h o l d s and c o l o r d i s c r i m i n a t i o n . E a r l y and l a t e t h r e s h o l d s t e n d t o be h i g h l y c o r r e l a t e d , and pe r h a p s we s h o u l d t a l k more c o n s e r v a t i v e l y about p r o c e s s e s s h a r e d i n common between r o d s and cones w i t h o u t t h e o r i z i n g about t h e a n a t o m i c a l groundwork i n v o l v e d . A n o t h e r p r o b l e m t h a t has been p o s t p o n e d u n t i l now i s a c u i t y as a confounded v a r i a b l e . There were c o r r e l a t i o n s between a c u i t y and d a r k a d a p t a t i o n f o r o l d n o r m a l s and young h y p e r t e n s i v e s . 100-Hue s c o r e s show the same r e l a t i o n s ; among o l d n o r m a l s and young h y p e r t e n s i v e s , d a r k - a d a p t a - . t i o n t h r e s h o l d s c o r r e l a t e d w i t h 100-Hue e r r o r s c o r e s ; t h e p r o b l e m i s t o d e c i d e i f a c u i t y a c c o u n t s f o r t h e a s s o c i a t i o n between c o l o r d i s c r i m i n a t i o n and d a r k - a d a p t a t i o n . The f a c t t h a t many c o r r e l a t i o n s a r o s e between f a r a c u i t y and d a r k a d a p t a t i o n makes t h e p r o b l e m somewhat l e s s a n n o y i n g , s i n c e n e a r a c u i t y ought t o be more i m p o r t a n t i n c o l o r v i s i o n t e s t i n g . P a r t i a l 182 c o r r e l a t i o n t e c h n i q u e s would p r o v i d e a more p r e c i s e answer. W i t h r e f e r e n c e , f i n a l l y , t o t h e l i t e r a t u r e on d a r k a d a p t a t i o n i n t h e c o l o r anomalous, t h i s s t u d y has added t o Fox's (1960) work by showing t h a t i n a group of s u b j e c t s b r o a d l y c l a s s i f i e d as anomalous t r i c h r o m a t s d a r k - a d a p t a t i o n s e n s i t i v i t y i s l o w e r e d . Dark A d a p t a t i o n and C l i n i c a l V a r i a b l e s The r e s u l t s have c o n f i r m e d p r e v i o u s r s e a r c h e s t h a t found an a s s o -c i a t i o n between d a r k — a d a p t a t i o n l o s s e s and r a i s e d IOP among eyes t h o u g h t t o be u n d e r g o i n g e a r l y open a n g l e glaucoma changes. A r o u g h s u b j e c t i v e i d e a o f t h e e x t e n t t o w h i c h t h e two v a r i a b l e s a r e a s s o c i a t e d can be g o t t e n i f we c o n s i d e r c r i t e r i a f o r s e l e c t i n g t h e f i v e w o r s e h y p e r t e n s i v e d a r k -a d a p t a t i o n c u r v e s . That i s , t h e r e a r e e x a c t l y f i v e p a t i e n t s whose c u r v e s a l m o s t w i t h o u t e x c e p t i o n f a l l above t h e n o r m a l c u r v e p l u s two s t a n d a r d d e v i a t i o n s , w h i c h i s t o say t h a t t h e y f a l l o u t s i d e t h e 95% c o n f i d e n c e i n -t e r v a l . (See F i g u r e <2.3r"' ) . I f we were t o s e l e c t o n l y h y p e r t e n s i v e s whose mean maximum IOP was 26 mm, o r h i g h e r , t h e s e f i v e p a t i e n t s p l u s two o t h e r s w o u l d be i n c l u d e d i n the group. No o t h e r c o l o r v i s i o n v a r i a b l e o r c l i n i c a l v a r i a b l e d i s c r i m i n a t e s as e f f i c i e n t l y as i n t r a o c u l a r p r e s s u r e so t h a t t h e f i v e worse c u r v e s and as few as p o s s i b l e of t h e r e m a i n i n g c u r v e s a r e s e l e c t e d . L e s t t h i s a s s o c i a t i o n appear;,>overly i m p r e s s i v e , keep i n , m i n d t h a t i t i n no v e r y s t r o n g way i m p l i c a t e s p r e s s u r e as a mechanisms, s i n c e i t i s , - - u r n j - i - i 4 — i ; : J~cjUre <£3. j .Atotr.WX&u-es/iotat curves + A S D. -"^rzJm^tCrJt'ati!! \.u.ti/e L _ . L _ . 1 |. ...j.- — — X.. n^rnnC /nc&n£urt/t\ *• AS.p. ! j j j i - a - r - J i i k ^ M 1 — i ^ ' M . f r ' a.tz. jhq ofiAf type*6dns<[t/es J&> *u£sfd.€J>...... L I . . j. I. #e <ts% confcolence. mczjrttaC for the Cut-i/es <L$ sAaum J_ :. °. the - J & ° z ^ iki T°? enters (see. te*t) 4, ;  i 1 5 ^5.1,^,3 «-.-ir-i-s-?~r-4 j ' " ' . n i l O - H — - I I I >l I I I I -J— I 5- 4 ~l f f ID II It- /J 7*/me (/Hirt) 184 possible that raised pressure accompanies the real cause of dark adapta-tion disturbances.also. Some support for vascular theories i s evident in the negative association between early yellow thresholds and diastolic blood pressure. The contrast with IOP correlations that occur for late BG thresholds almost exclusively, i s of some interest. Possibly the two-filter method is powerful enough to separate destruction of a visual process into com-ponents (rod and cone specific as to wavelength, here) that are referable to certain aspects of the disease process (IOP, i t s cause or effect, or 2 lowered blood pressure, i t s cause or effect). Finally, can the effects of hypertension be related to the tradi-tional distinctions made between neural and photochemical mechanisms of dark-adaptation, once we have admitted that pre-retinal changes contribute some part of the effect? One obvious, yet important, point here i s that losses i n neural functioning, i f they exist, are not necessarily of the same kind as the losses which result i n scotomas that trace fiber bundles distributions. If i t i s true that the rise in old yellow rod thresholds represents a break-down of rod processes in hypertensives within a "normal" concentric cir c l e around the 2° rod-free fovea, then the expectation i s that i n areas with higher rod densities even greater losses w i l l be found. The whole retina becomes suspect then, and we are tempted to look for the causes of degeneration across the whole retina, not just around the disc where large fibers exist. Just as faltering nutrition to the nerve head 185 h a s b e e n s u g g e s t e d a s t h e c a u s e o f t h e t r a d i t i o n a l g l a u c o m a t o u s s c o t o m a s , s o i t m i g h t b e r e s p o n s i b l e f o r t h e m o r e i n s i d i o u s e a r l y d e t e r i o r a t i o n o f o t h e r a r e a s , a l t h o u g h n o t n e c e s s a r i l y a t t h e l e v e l o f t h e m a i n t r a n s m i s s i o n l i n e s . T h i s s p e c u l a t i o n r e v o l v e s a r o u n d d i s r u p t i o n o f n e u r a l p r o c e s s e s b e c a u s e i t i s a f a m i l i a r i d e a i n g l a u c o m a r e s e a r c h , b u t a t t h i s p o i n t p h o t o c h e m i c a l p r o c e s s e s a r e e q u a l l y g o o d c a n d i d a t e s s i n c e t h e t w o f i l t e r m e t h o d a s u s e d h e r e i s u n a b l e t o d i s t i n g u i s h b e t w e e n t h e m . 186 FOOTNOTES "Sfedia changes seem more l i k e l y s i n c e the subjects were screened for macular pigmentation changes i n the c o l o r v i s i o n study. 2 The BG rod curve monopoly on c o r r e l a t i o n s (with c l i n i c a l v a r i a b l e s and anomaloscope v a r i a b l e s , f o r instance) may a l s o be due to a combination of f a c t o r s : (1) BG rod t h r e s h o l d c o r r e l a t i o n s w i t h BG cone t h r e s h o l d s , (2) BG rod t h r e s h o l d c o r r e l a t i o n s w i t h Y cone t h r e s h o l d s , (3) The fact that the BG rod curve i s the lowest of any p o r t i o n of any curve, and may therefore f o l l o w the v a r i a b i l i t y of another measure more c l o s e l y . 187 B I B L I O G R A P H Y A d a i r , E . R . , D u r a t i o n a n d l i g h t - d a r k r a t i o o f i n t e r m i t t e n t p r e - a d a p t a t i o n a s f a c t o r s i n f l u e n c i n g h u m a n d a r k a d a p t a t i o n , J.O.S.A.3 1 9 5 3 , 4 3 _ , p p . 2 2 - 2 7 . A k c h u r i n a , D y n a m i c s o f v i s u a l d a r k a d a p t a t i o n i n G l a u c o m a . Vestrik Oftalmologii, 1 9 6 1 , 7 4 _ , p p . 2 5 - 2 8 . A n i n a , F . T . , D a r k a d a p t a t i o n i n G l a u c o m a . Optamolgvschiski furnal3 1 9 5 8 , 2 , p p . 8 5 - 9 0 . A r d e n , G . B . , W e a l e , R . A . , N e r v o u s m e c h a n i s m s a n d d a r k a d a p t a t i o n . J. Physiol.,, 1 9 5 4 , 1 2 5 , p p . 4 1 7 - 4 2 6 . A u e r b a c h , E . , a n d W a l d , G . I d e n t i f i c a t i o n o f a v i o l e t r e c e p t o r i n h u m a n c o l o r v i s i o n , Science, 1 9 5 4 , 1 2 0 , 4 0 1 - 4 0 5 . B a k e r , G . , A . D e b o n s , a n d D . F . 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Yudkin, Effect of age on dark adaptation; J. Physiol.3 1944, 103, pp. 1-8. Rowland, W.M., and L.L. Sloan, The relative merits of red and white light of low intensity for adapting the eyes to darkness , J.O.S.A.3 1944, 34, pp. 601-604. Rushton, W.A.H., Visual adaptation. Proc. Roy. Soc. 3 (Biol.), 1965a, 20, 162. , The nervous and chemical organization of dark-adaptation. Trans, 'ophthal. Soc. V.K.3 1965b, 85, pp. 679-681. , Bleached rhodopsin and visual adaptation. J. physiol.3 1965c, 181, pp. 645-655. , and R.D. Cohen. Visual purple level and the course of dark-adap-tation. Nature3 1954, 173, pp. 301-302. , Fulton, A.B., and Baker, H.D., Dark-adaptation and the rate of pigment regeneration, l£s. Res.3 1969, 9_, pp. 1473-1479. 196 Semenoff, B., Dark adaptation during stimulation with coloured light, Br. J. Psychol., 1941, XXXII, Part 2, pp. 9-154. Sharpley, T.W. , The dark-adaptation of miners suffering from nystagmus, ft?. J. Ophthal., 1948, 32, pp. 199-204. Shlaifer, A., A review of recent literature on Glaucoma, Am, J. Optome^ try, 1967, pp. 471-489. Sloan, L.L., Instruments and techniques for the c l i n i c a l testing of light sense. Arch, ophthal., 1939, 21^ , pp. 913-934. , Instruments and techniques for the c l i n i c a l testing of the light sense. IV. Size of pupil as a variable factor i n the determina-tion of the light minimum, Arch, ophthal., 1940, 24, pp. 258-275. , The threshold gradients of the rods and cones: in thedark«^adapted and the partially light adapted eye, Am, J, ophth,, 150, pp. 1077-1089. Smith, S.W. , A. Morris and F.L. Dimmick, "Effect of exposure to -various red lights upon subsequent dark-adaptation measured by the method of constant stimuli, J.O.S.A., 1955, 45, pp. 502-506. Spaeth, E.B., Cl i n i c a l determination of the light threshold, Arch, ophthal., 1934, IL, pp. 462-485. Steven, D.M., Relation between dark-adaptation and age, Nature, London, 1946, 157, pp. 376-377. Stewart, W.C., H.D. Madell, and A.M. Dyer, Night vision in the myotic eye. Canadian ¥ ed. Assoc. J., 1968, 99^ , pp. 1145-1148. Thompson, L.C. The nervous system in visual adaptation. Br. J. ophthal., 1950, 34, pp. 129-146. Trusov, M.C. Investigation of dark-adaptation in a cubicle with l i g h t -f i l t e r s i n cases of glaucoma. Yetnik Oftalmologii, 1962, 5_, pp. 34-38. Tsintsadze, V.I., Adaptometric water test in glaucoma. Vescoivuznaia. Konferentsiia of'talmologov, 2nd T i f l i s , 1961, Respublikanskoe nauch ob-vo of'taldmologov Gruzinksoi, USSR, Abstract Sec. 12, p. 110, ExcerptaM edica. 197 Tsintsadze, V.I., Adaptometric water test in glaucoma. Materialy Pervoi Republikonskoi Konferentsii Of 1talmologov Gruzii, 1961, abstrac-ted i n ExoerptaMedioa, 1962, p. 510 (ophthalmology series). Verriest, G., Les deficiences acquises de l a discrimination chromatique. Mem. Aaad. Roy. Med. Belg..,1964, Series 2,4, Fasc. 4, 35. , and G. 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Physiol., 1937, _ n , pp. 93-105. , and Auerbach, "The participation of different types of cones in human light and dark adaptation," Am. J. Ophthal., 1955, 39_, 24, pp. 24-40. Walters, H.V. and W.D. Wright, The spectral sensitivity of the fovea and extrafovea i n the Purkinje range. Proa. Roy. Soo., B. 1943, 131, pp. 340-361. Winsor, CP. and A.B. Clark, Dark adaptation after varying degrees of light adaptation. Proa. Natl. Aaad. Soi., 1936, £ 2 , pp. 400-404. 198 Woiska, P.H., An evaluation of the dark test, Am. Int. Med., 1944, 21, pp. 101-118. Wolf, E., and M.J. Zigler, Dark-adaptation and size of te s t f i e l d , J.O.S.A., 1950, 40, 4, pp. 211-218. Wolf, E., and M.J. Zigler, Dark-adaptation and duration of testflash, J.O.S.A., 1951, 41, 2, pp. 130-133. , Location of the break i n the dark-adaptation curve in relation to pre-exposure brightness and pre-exposure time, J.O.S.A., 1954, 44^  pp. 875-879. , Course of dark-adaptation under various conditions of pre-exposure and testing," J.O.S.A., 1955, 45, 9, pp. 696-702. Wulfeck, J.W. , D.C. Johannsen, and P.I. McBrider-, Studies on dark-adapta-tion III. Pre-exposure tolerance of the human fovea as measured by contrast sensitivity, J.O.S.A., 1960, 50, pp. 556-558. Zbarskii, S., The importance of the width of the pupil i n investigations of adaptation to dark i n Glaucoma patients, Oftdlm. Zh., 2_, pp. 81-85, as abstracted in ExoevptaM edioa, 1960, Section 12, p. 510. Zigler, M.J., Wolfe, and E.S. King, The influence of surrounding bright-ness and short wave components of radiation on dark-adaptation J.O.S.A., 1951, 41, pp. 354-359. Zuege, P. and S.M. Drance, Studies of dark adaptation of discrete para-central retinal areas. Part I. Paper read at Canad. ophthal. Soc, June, 1966. , Studies of dark-adaptation of discrete paracentral retinal areas in glaucomatous subjects, Am. J. Ophthal., 1967, 64, 1, pp. 56-63. , Studies of dark-adaptation of discrete paracentral retinal areas Part II. Canad. J. ophthal., 1967, 2, pp. 35-40. 199 APPENDIX A TABLE I NINE STUDIES DESIGNED TO EXPLORE THE EFFECT OF PRE-ADAPTATION INTENSITY "VARIATION AT CONSTANT DURATIONS: RANGES OF INTENSITIES AND DURATIONS 1. CP. Winsor and A.B. Clark, 1936 2. S. Hecht, C. Haig, A. Chuse, 1937 Intensities 12 mL, 120 mL, 1430 mL 263, 3,800, 19,500 38;900, 400,000 Photons Durations 5 min. 2 min. 3. J.W. Craik and M.D. Vernon, 1941 4. B.H. Crawford, 1937 5. B.H. Crawford, 1940 6. B.H. Crawford, 1947 7. C. Haig, 1941 8. G. Wald and A.B. Clark, 1937 9. F.A. Mote and A.J. Riopelle, 1951 1.2, 12, 120, 300, 1.200, 3,000, 12.000, 30.000 efc. 132, 78, 1.55, 79, 1.48, 0.041, 0.000174, 1.59, 0.043, 0.000178 C/ft2 440, 710, 69 C/ft2 0.005, 0.0017, 0.006, 0.017, 0.06, 0.15, 0.4, 1.7, 6, 15, 48, 140 C/sq. f t . 4, 20, 44, 447, 1150, 2090, 4700 mL 30.3, 105, 643, 3.6, 245, 750, 1890 ml. 3 min. 5 min. 1 min. 0.5 sec. 4 min. 7 min. 5 sec. 565, 1130, 5,650, 11.300 mL. 30 sec. 565, 1130, 5.650, 11.300 mL. 150 sec. 565, 1130, 5.650, 11.300 mL. 300 sec. Unit Conversions: 3.184 cd/mz = 1 mL. 1 efc = 3.426 cd/m2 1 cd/ft. 2 = 10.764 cd/m2 1 photon = 1 cd/m2 at 1 mm? pupil TABLE I I THE EFFECTS OF PRE-ADAPTATION SIZE AND RETINAL LOCATION ON DARK ADAPTATION: VALUES OF THE VARIABLES IN THREE EXPERIMENTS See t e x t f o r e x p l a n a t i o n Honda,1953* Hanson e t a l . , 1960 C r a w f o r d , 1940 P r e - a d a p t a t i o n L o c a t i o n 0° + 8° h o r i z o n t a l l y °o + 8 ° h o r i z o n t a l l y P r e - A d a p t a t i o n S i z e 3° 70° 1°,2.5° " s m a l l " " i n t e r - " l a r g e " 5°, 10°, X*** m e d i a t e " 37.5° ^ ' / ^ _ ©o 0 0 10.3°, 3.06° 1.09°, 0.33° 0.14° 9° + 60° P r e - A d a p t a t i o n I n t e n s i t y 60 l u x & 150 l u x 1 f t . L , 10 s e c . 10 f t . L , 10 s e c . An i n t e n s i t y s u c h t h a t f o r a s p e c i -7 1 0 C / f t . 2 and „ 6 9 C / f t . f o v i a l -4 4 0 C / f t . ' D u r a t i o n b o t h f o r 5 min. 100 f t . L , 10 s e c . + f i c s i z e p r e - a d a p -t a t i o n f i e l d t h e p e r i p h e r -a l l y 1000 f t . L . , 100 s e c . 0.1 f t . L , 10 s e c . d i f f e r e n c e t h r e s h o l d l y f o r b r i g h t n e s s = 1 c / f t z . d u r a t i o n n o t s p e c i -f i e d one m i n u t e T e s t P a t c h S i z e and D u r a t i o n 3° d u r a t . n o t sp e c . 1° 0.033 s e c . 1° 0.033 s e c . 0.49° 1 s e c . 0.50° 1 s e c . T e s t P a t c h L o c a t i o n 1.5° 0° 2°, 6°, 15° h o r i z o n t a l l y c o n c e n t r i c w i t h pre-a d a p t a t i o n f i e l d c o n c e n t r i c w i t h p r e - a d a p t a t i o n f i e l d * As c i t e d b y Hanson, A n d e r s o n and W i n t e r b e r g , 1960, p. 895. o o TABLE III The Effects of Pre-Adaptation and Test Color on Dark Adaptation Paper Pre-Adaptation Color(s) Test Patch Color(s) Test Patch Location Zigler, Wolf & King, 1951 UV white (?) fovea + 6° peripherally Wolf & Zigler, 1955 UV white, blue, green,red 7° peripherally Hecht & Hsia, 1945 Red, white blue 7° peripherally Lowry, 1943 Red, white white fovea Rouland & Sloan, 1944 Red, white white 15° peripherally Miles, 1943 White, then red violet 7° peripherally Miles, 1953 White, then red or blue violet 7° peripherally Semenoff, 1941 White or red Red during late adaptation r,o,b, throughout dark adapta-tion time white(?) white (?) white (?) 40° peripherally it ti it II Smith, 1955 Morris & Diftaiick White, reds (626 mj, 640 mu) 675 mu, 690 mu) white 10° peripherally Hecht, Haig & Chase, 1937 white violet, red 30° peripherally MacLeod & Bartlett, 1954 White white, blue fovea & ll°20f peripherally Crawford, 1947 Green, red white fovea Dodt & Jessen, 1961 Blue, orange white (erg) Wald, 1960 White White violet, yellow red,yellow 6°, 1°,2°,6°,10° peripher-a l l y and Foveally 0°-10° Lie, 1959 White(?) blue,yellow,orange,red 7.5° peripherally Dodt & Jessen, 1960 White blue, red (erg) Des, 1964 Orange (600 mu) 444 mu, 480 mu, 450 mu, 460 mu, 540 mu, 500 mu, 520 mu fovea Auerbach & Wald, 1954 White, yellow, orange, orange-Orange , orange-red -red violet, orange yellow-g, blue-e. 6° peripherally Mandelbaum & Mintz, 1941, V, BG, 0, 0-R, G, Y 0, 0-R R, V, G BG, BV, V, YG fovea Note: (?) means that the variable was not specified in the paper. continued ro o P a p e r P r e - A d a p t a t i o n C o l o r ( s ) T e s t P a t c h C o l o r ( s ) T e s t P a t c h L o c a t i o n Hanson & A n d e r s o n , 1960 W h i t e , r e d , g r e e n , b l u e w h i t e , r e d , g r e e n b l u e i n a l l c o m b i n a t i o n s f o v e a Wald & Aurbach, 1965 Green White Orange B l u e Y e l l o w Orange, r e d Orange, r e d W h i t e b l u e - g r e e n , r e d y e l l o w , v i o l e t , orange v i o l e t , o r a n g e , y e l l o w - g r e e n v i o l e t , orange v i o l e t , orange v i o l e t , o r a n g e , b l u e - g r e e n v i o l e t , o range v i o l e t , o range 6 p e r i p h e r a l l y f o v e a 90° p e r i p h e r a l l y Dodt & E l e n i u s , 1960 White w h i t e , o r a n g e , e r g . TABLE IV Age and Dark Adaptation Paper Ages Investigated Rod Thresholds Rod Rate Cone Threshold Cone Rate Threshold Variability Between Ss Age at Which Deterio-ation Begins to In-crease Sharply Verriest 1969 3-29 decrease from 3 to 13 decrease with age decrease from 3-13 increases with age Robertson & Yudkin, 1944 14-71 increases with age increases with age Birren, Bick & Fox ,1948 12-83 increases with age increases with age post-60 shows largest effect on rod thresho] McFarland & Fisher, 1955 20-60 increases with age slowly for young-est & old-est McFarland, Domey, Warren & Wand, 1960 16-89 increases with age increases with age no increase with age. (constant with age) Domey, McFarland & Ghadwick 16-89 increases with age decreases with age increases with age decreases with age 1960 Domey, McFarland, 1961 16-89 increases with age at each min. increases with age at each min. Steven, 1946 10- 60 increases with age increases with age post-40 White, Derby & Kirk, 1925 18-65 find no difference increases with age Sharpley, 1948 10-70 increases with age post-40 ro o Paper Ages Investigated Rod Thresholds Rod Rate Cone Thresholds Cone Rate Threshold Variability Between Ss Age at Which Deterior' ation Begins to In-crease Sharply L uria, 1960 20-73 increases with age (though rods or cones not specified) 40-50 Birren & Shock, 1950 40-83 increases with age no age effect increases with age no age effect Hecht & Mandelbaum, 1939 15-65 no increase with age increases with age Woisker, 1943 15-78 increases with age (rods or cones not specified) post-40 Booher & Williams, 1938 15-50 increases with age Korb, 1939* no change with age S tewart, 1941* increases with age Juans, Blanchard * Sutterthwaite no change with age * Cited by Robertson and Yudkin, 1944. ro o TABLE V Glaucoma and Dark Adaptation Paper Clin i c a l Categories Pre-adaptation intensity, duration test location Values of normal + glaucoma depen-dent dark adapta-tion variables compared  Dependent dark adapta-tion variables: corre-lations with c l i n i c a l variables Mackie, Chadwick & Jordan, 1961 Moller, 1925 Not specified Not specified 35 min. threshold taken after unspecified pre-adaptation and with un-specified testfield. 35-45 min. dark adapta-tion threshold taken after unspecified pre-adaptation—with unspe-cifi e d testfield no normals investigated no comparisons are made reduced sensitivity compared to normals high correlation between quantitative f i e l d loss and dark adaptation in glaucoma, negligible relation be-tween f i e l d loss and dark adaptation Delaney, 1930 (he em-ploys the same appa-ratus as Moller, 1925} Zuege & Drance, 1967a,b, 1966 Full glaucoma Early glaucoma (i.e. glaucomatous IBate & some disc changes normal=full f i e l d , normal IOP, history, outflow, + disc advanced glaucoma = high IOP, f i e l d losses 10 min. at 7 ft.C.j ob-tains the 30 min. threshold same 3000-3250 aps. for 5 min. tested at 15°, 30°, 5°, 45° from blind spot. 1/2° test patch reduction in sensitivity dark adaptation related compared to normals more to acuity than to depends on "the stage f i e l d losses, of the disease no changes advanced glaucoma shows elevated thresholds within the area of a f i e l d defect', 30 min. threshold i n the same area for a hypertensive i s normal ratio of 15 threshold to 30° threshold at 30 min. dark adaptation <(5 (ft*} raised among hypertensives within enlarged blind spot (b) is raised among glau-comas with poor cup and no f i e l d defects within the area tested ro o Ul C l i n i c a l C a t e g o r i e s P r e - a d a p t a t i o n i n t e n s i t y , d u r a t i o n t e s t l o c a t i o n u n i l a t e r a l glaucoma p e r i p a p i l l a r y r e g i o n & & " s u s p e c t s " 15° v e r t i c a l t e s t e d under a w a t e r l o a d n ormals glaucomas c l a s s e d a c c o r d i n g t o f i e l d l o s s s e v e r i t y and IOP e l e v a t i o n n ormals glaucomas $ s u s p e c t s ( i . e . , g l a u c o m a t o u s mate) a r r e s t e d e a r l y com-p e n s a t e d glaucoma, a r r e s t e d advanced compensated glaucoma, a r r e s t e d advanced subcompensated glaucoma , a r r e s t e d advanced uncompensatable glaucoma s i m p l e d e v e l o p e d un-compensated glaucoma 10 min. p r e - a d a p t a t i o n n o t s p e c i f i e d n o t s p e c i f i e d V a l u e s o f no r m a l & glaucoma depen de n t d a r k a d a p t a t i o n v a r i a b l e s compared  l o w e r e d s e n s i t i v i t y w i t h a w a t e r l o a d compared t o n o r m a l s i n p e r i p a -p i l l a r y a r e a , b u t n o t 15° v e r t i c a l l y r a i s e d p r e s s u r e c o r r e l a t e s w i t h p o o r d a r k - a d a p t a t i o n ; c o n c e n t r i c n a r r o w i n g o f the f i e l d does a l s o Dependent d a r k a d a p t a -t i o n v a r i a b l e s : c o r r e -l a t i o n s w i t h c l i n i c a l v a r i a b l e s d a r k a d a p t a t i o n i n IOP & " p r o g r e s s o f t h e glaucoma- & suHpents d i s e a s e " a r e a s s o c i a t e d i s i m p a i r e d w i t h d a r k a d a p t a t i o n l o s s e s L o s s o f d a r k a d a p t a t i o n s e n s i t i v i t y w i t h l o w e r i n g o f IOP by m i o t i c s j i n c r e a s e i n IOP l e a d s t o l o s s o f d a r k a d a p t a t i o n • s e n s i t i v i t y o r no c h a n g e 9 a c u i t y and f i e l d d e f e c t s a r e a s s o c i a t e d w i t h d a r k a d a p t a t i o n l o s s e s ro o C l i n i c a l C a t e g o r i e s P r e - a d a p t a t i o n i n t e n s i t y , d u r a t i o n t e s t l o c a t i o n " w e l l e s t a b l i s h e d glaucoma" ( i . e . , f i e l d changes, p r e s s u r e changes, o r d i s c changes p r e -s e n t ) 1500 mL, 3 min. 7° t e m p o r a l . V i o l e t t e s t mate o f a g l a u c o -matous eye n o t s p e c i f i e d " e s t a b l i s h e d glaucoma" ( i . e . IOP, f i e l d & d i s c c han-g e s — a l l o r some ) , normals 100 w a t t s , 3 min. 1250 a p s . , 10 min. V a l u e s o f n o r m a l & glaucoma depen-d e n t d a r k a d a p t a -t i o n v a r i a b l e s compared  p h o t o c h r o m a t i c i n -t e r v a l and p o i n t show no d i f -f e r e n c e s from n o r -m a l s ; e l e v a t e d f i n a l r o d o r cone t h r e s h o l d i n t h e c l i n i c a l g r o u p , o f t e n i n s p e -c i f i c p e r i p h e r a l a r e a s o n l y c l i n i c a l c u r v e s f a l l between n o r m a l & glaucomatous c u r v e s i n r e g a r d t o r a t e & f i n a l t h r e s h o l d r a t e changes, f i n a l t h r e s h o l d changes & " r o d s u p p r e s s i o n " Dependent d a r k a d a p t a -t i o n v a r i a b l e s : c o r r e -l a t i o n s w i t h c l i n i c a l v a r i a b l e s 20/34 glaucomatous eyes show e l e v a t e d d a r k a d a p t a -t i o n t h r e s h o l d s a s s o c i a -t e d w i t h f i e l d c hanges, o f t e n s p e c i f i c t o a r e t i -n a l a r e a . d i s c changes & h i g h IOP u s u a l l y p r e c e d e o r f o l l o w c l o s e l y t h e d a r k a d a p t a t i o n l o s s e s ; o r d a r k a d a p t a t i o n may r e m a i n n o r m a l a f t e r glaucoma i s e s t a b l i s h e d d a r k - a d a p t a t i o n l o s s e s a r e a s s o c i a t e d w i t h f i e l d c hanges, n o t w i t h a c u i t y , n o r w i t h t h e IOP improvement i n a c u i t y , f i e l d , IOP a r e accompanied by d a r k - a d a p t a t i o n i m -provement ro o —J Paper J a y l e , Ourgaud, B e r a r d , 1948 C l i n i c a l C a t e g o r i e s P r e - a d a p t a t i o n i n t e n s i t y , d u r a t i o n t e s t l o c a t i o n w hole eye t e s t e d 3 min. p r e - a d a p t a t i o n V a l u e s o f normal & glaucoma depen-dent d a r k - a d a p t a -t i o n v a r i a b l e s compared f o r glaucomas i n i t i a l i n t e n s i t y i s r a i s e d , f i n a l t h r e s h o l d i s n o t , and t h e p o i n t Dependent d a r k adapta-t i o n v a r i a b l e s : c o r r e -l a t i o n s w i t h c l i n i c a l v a r i a b l e s mav be o b l i t e r a t e d Ourgaud & N o r m a l s : i . e . o u t -A u b e r t , f l o w , IOP, p r o v o c a -1958 t i v e t e s t s n o r m a l , Glaucomas: good a c u i t y , f i e l d chan-ges, d i s c c h a n g e s , " S u s p e c t s " : mate o f a glaucomatous eye, p o s i t i v e f a -m i l y h i s t o r y , d i s c changes, s m a l l f i e l d changes, o r r a i s e d IOP 3 min., 11 UL psb n o r m a l s & s u s p e c t s have e q u i v a l e n t c u r v e s up t o 20 m i n . glaucomas have a r a i s e d c u r v e throughout> n o r m a l s & s u s p e c t s a l s o have a l m o s t i d e n t i c a l r a n g e s o f t h r e s h o l d s each m i n u t e , glaucomas have an expanded r a n g e > s t a t i s t i c a l s i g n i f i c a n c e o f t h e d i f f e r e n c e between n o r m a l s & s u s p e c t s a f t e r 20 m in. i s d o u b t f u l . i m p a i r e d o u t f l o w f a c i l i t y s e p a r a t e s s u s p e c t s so t h a t t h e i r c u r v e s a r e s t a t i s t i -c a l l y d i f f e r e n t f r o m n o r -mal c u r v e s H o u s s i n , 1949 Good a c u i t y , poor d i s c , p o o r f i e l d one min. p r e - a d a p t a t i o n r a i s e d 3 m i n . t h r e s h o l d P o o r a c u i t y , good f i e l d same n e g l i g i b l e d i f f e r e n c e s H y p e r t e n s i v e s w i t h t r e a t e d IOP's same s m a l l e r d i f f e r e n c e s t h a n under r a i s e d TOP " S u s p e c t s " ( i . e . p a i n , h a l v e s , haze) same s l i g h t l y r a i s e d t h r e s h o l d s C o n t ' d . . ro o CD Paper Clinical Categories Pre-Adaptation intensity, duration test location Akchurina. 1961 "normals" "i n i t i a l glaucoma" not specified same "established glaucoma" same "advanced glaucoma" same various stages of same glaucoma treated with novocain, diabazol, or oxygen glaucoma treated sur- same gically (established and advanced glaucoma) Dubois- "established glaucoma" Poulson & "suspects" (i.e. IOP Magis, raises or field chan-1960 ges, or family history) 11 UL.psb., 3 or 5 min Values of normal & glaucoma depen-dent dark-adapta-tion variables compared  Dependent dark adapta-tion variables: corre-lations with clinical variables sensitivity within low, normal values dark adaptation worse than for i n i t i a l glaucoma dark adaptation sharply curtailed dark adaptation im-proved over non-drug condition no dependence of dark-adaptation on IOP or condition of disc dark adaptation asso-ciation with IOP dark adaptation correla-ted with field losses & IOP dark adaptation im-proved or not im-proved over pre-sur-gical curves  no relation between sur-gically lowered IOP and dark adaptation at 25-30 min. "suspects" show higher-than-normal thresholdsJ glaucoma thresholds are high throughout dark adaptation. Although these effects are sta- tistically significant, the authors conclude that individual varia-tions are too great for dark adaptation to be used as a diagnostic tool. dark adaptation losses aren't correlated with IOP changes induced by drugs', however, the effect of the drug on the metabolism of photo-pigments is confounded with the effect of IOP here, quotes statistical studies: high IOP is associated with raised dark adaptation thresholds in "suspects". Those eyes having positive provocative tests show like-r- *- I J Paper C l i n i c a l C a t e g o r i e s P r e - a d a p t a t i o n i n t e n s i t y , d u r a t i o n t e s t l o c a t i o n V a l u e s o f n o r m a l & glaucoma depen-dent d a r k adapta-t i o n v a r i a b l e s compared Dependent d a r k a d a p t a -t i o n v a r i a b l e s : c o r r e -l a t i o n s w i t h c l i n i c a l v a r i a b l e s D u b o i s -P o u l s o n & M a g i s , 1960 ( c o n t ' d ) w i s e , r a i s e d d a r k a d a p t a -t i o n t h r e s h o l d s . M e s o p i c & s c o t o p i c f i e l d changes a t 20° & 30° c o r r e -l a t e d w i t h d a r k a d a p t a t i o n changes ( a l t h o u g h t h i s h a s n ' t been j u s t i f i e d s t a -F r a n c o i s , V e r r i e s t & DeRouk, 1957 C o n g e n i t a l n o t s p e c i f i e d glaucoma p o i n t o f t h e g l a u -coma i s r e t a r d e d , t h r e s h o l d s i n r o d & cone p o r t i o n a r e r a i s e d , b u t the f i n a l t h r e s h o l d may be n o r m a l J a y l e & I n i t i a l : A c u i t y n o r - n o t s p e c i f i e d most s e v e r e glaucoma c u p p i n g i s r e l a t e d t o d a r k Ourgaud, m a l , no f i e l d chan- has most abnormal a d a p t a t i o n w h i c h i s i t s e l f 1950 c i t i n g ges, no d i s c changes, c u r v e s . r e l a t e d t o t h e " p r o g r e s s J a y l e , IOP v a r i a b l e . f i n a l t h r e s h o l d s o n l y o f the d i s e a s e " , a l t h o u g h Ourgaud, I . f i e l d c o n t r a c - c o n sidered J e v e n w i t h - t h e r e i s g r e a t i n d i v i d u a l B e r a r d & t i o n , d i s c e x c a v a - ou t p u p i l c o r r e c t i o n s v a r i a t i o n . C r o i s y , t i o n , 8/10 a c u i t y , d i f f e r e n c e s a r e appa-1950 b u t h i g h IOP v a r i a b l e . r e n t . Groups I I & I I I u n l i s t e d I I . n a s a l d e f e c t , h a r d l y change i n r e l a -i n t h e i r B j e r r u m ' s scotoma, t i o n t o n o r m a l s w i t h r e f e r e n - 5/10-8/10 a c u i t y , a p u p i l c o r r e c t i o n . c e s d i s c e x c a v a t i o n & I n i t i a l & I f a l l more p a l l o w , IOP h i g h & o f t e n w i t h i n a n o r m a l n o t v a r i a b l e . r a nge & i n i t i a l s more ( c o n t i n u e d ) .... so t h a n I . c o n t ' d . ro o P a p e r C l i n i c a l C a t e g o r i e s P r e - A d a p t a t i o n i n t e n s i t y , d u r a t i o n t e s t l o c a t i o n V a l u e s o f n o r m a l & Glaucoma depen-dent d a r k - a d a p t a -t i o n v a r i a b l e s compared  Dependent d a r k adapta-t i o n v a r i a b l e s : c o r r e -l a t i o n s w i t h c l i n i c a l v a r i a b l e s I I I . D i s c p a l l o r , IOP n o t c o n t r o l a b l e w i t h d r u g s , 2/10-5/10 a c u i t y . T e r m i n a l - l o o s o f c e n t r a l v i s i o n , t e m p o r a l i s l a n d , c u p p i n g , " n o r m a l s " W a i t e , Derby & K i r k , 1925 " e s t a b l i s h e d " g l a u -coma ( i . e . , IOP, d i s c & f i e l d chan-ges) "glaucoma s u s p e c t s " ( i . e . n o rmal mate o f a glaucomatous eye) 3 mL, 10 min. 2°5' x 4°10' f o v e a l same r a t e & f i n a l t h r e s h o l d among n o r m a l s , t h e r e i s no show l o s s e s compared t o r e l a t i o n between age and n o r m a l s ( a g e - c o r r e c t e d ) d a r k - a d a p t a t i o n up t o 10 min. o f d a r k a d a p t a t i o n , same o r between d a r k - a d a p t a t i o n and c o r r e c t i v e l e n s e s , o r between d a r k a d a p t a t i o n & pigment d e p o s i t s , o r between d a r k a d a p t a t i o n & p i l o c a r -p i n e , o r between d a r k - a d a p -t a t i o n & o r d e r o f eye t e s -Derby, W a i t e & K i r k , 1926 s u s p e c t s f r o m t h e 1925 s t u d y who have d e v e l o p e d glaucoma p l u s some a d d i -t i o n a l glaucomas same as above same as above r i s e s i n t h r e s h o l d p r e c e d e development of glaucoma i n t h e s u s p e c t eve Sp a e t h , 1934 glaucoma " a l l types"t c h r o n i c , s i m p l e , 5 f o o t c a n d l e s , 20 min. f o v e a l 72° x 72° t e s t glaucomas & s u s p e c t s show i n c r e a s e d a c u t e . Secondary j s u s p e c t s ( i . e . i n -c r e a s e d IOP) norm a l s p a t c h t h r e s h o l d s ro c o n t ' d . P a p e r C l i n i c a l C a t e g o r i e s P r e - a d a p t a t i o n i n t e n s i t y , d u r a t i o n t e s t l o c a t i o n V a l u e s o f n o r m a l & glaucoma depen-d e n t d a r k a d a p t a -t i o n v a r i a b l e s compared  Dependent d a r k adapta-t i o n v a r i a b l e s : c o r r e -l a t i o n s w i t h c l i n i c a l v a r i a b l e s Derby, C h a n d l e r & O ' B r i e n , 1928 N o r m a l s : (1) no r m a l eye o f a glaucomatous mate (2) s l i g h t d i s c changes o r s l i g h t IOP r i s e s ; Glaucomas: (1) d i s c & IOP changes, no f i e l d changes, (2) s l i g h t f i e l d changes, d i s c changes, IOP r i s e s , (3) e s t a b l i s h e d g l a u -coma w i t h d i s c , IOP & f i e l d changes  2.6 mL, 12 min. and 18 mL, 10 min. Glaucomas' r a t e t o a No c l i n i c a l s i g n s o f g l a u -n o r m a l f i n a l t h r e s h o l d coma need be p r e s e n t f o r i s d e l a y e d o r a n o r m a l ; d a r k a d a p t a t i o n l o s s e s t o f i n a l t h r e s h o l d i s a p p e a r , n e v e r a t t a i n e d Ourgaud & E t i e n n e , 1961, c i t i n g J a y l e , Our-gaud & A u b e r t , 1959 L o n g i t u d i n a l s t u d i e s show t h a t d a r k a d a p t a t i o n v a r i e s w i t h IOP f o r l o n g t e r m i n d i -v i d u a l c u r v e s , b u t s h o r t term c u r v e s v a r y w i t h f i e l d changes & IOP  Ourgaud, E t i e n n e , 1961 c i t i n g B e r a r d & C r o i s y , undated & u n l i s e d i n t h e i r r e -f e r e n c e s a c u t e and s e c o n d a r y g l a u -coma c u r v e s v a r y w i t h IOP c o n t ' d ro ro P a p e r C l i n i c a l C a t e g o r i e s Pre-Adap t a t i o n i n t e n s i t y , d u r a t i o n t e s t l o c a t i o n V a l u e s o f n o r m a l & Glaucoma depen-dent d a r k - a d a p t a -t i o n v a r i a b l e s compared  Dependent d a r k a d a p t a -t i o n v a r i a b l e s : c o r r e -l a t i o n s w i t h c l i n i c a l v a r i a b l e s M e d u r i , Puddu & A n s e l m i , 1968 Glaucomas: I : 2-3 mo. o f d i s e a s e , IOP =26, e x t e n s i v e f i e l d & d i s c changes not s p e c i f i e d Ourgaud, E t i e n n e , 1961 I I . 4-12 mo. o f d i s -e a s e , H i g h IOP, s m a l l f i e l d & d i s c changes, IOP = 31 same I I I . S m a l l d i s c & f i e l d changes, IOP = 21 same Ourgaud & E t i e n n e , 1961 c i t i n g J a y l e , Ourgaud, B e r a r d & C r o i s y , 1950 b u t u n l i s t e d i n t h e i r r e f s . t o t a l eye p h o t o p i c & s c o t o p i c t h r e s h o l d e l e v a t i o n f i e l d , d i s c , & a c u i t y chan^-ges c o r r e l a t e w i t h d a r k a d a p t a t i o n changes' e x p e r i -m e n t a l IOP i n c r e a s e s p r o -duce d a r k a d a p t a t i o n changes  l i t t l e d i f f e r e n t f r o m n o r m a l e x p e r i m e n t a l h y p e r t e n s i o n p r o d u c e s r a i s e d d a r k adap-t a t i o n t h r e s h o l d s no d i f f e r e n c e s f r o m n o r m a l s m a l l e f f e c t o f an e x p e r i -m e n t a l IOP r i s e ; f a m i l y h i s t o r y , f i e l d chan-g e s , d i s e a s e d u r a t i o n , age a r t e r i a l b l o o d p r e s s u r e don't c o r r e l a t e w i t h d a r k a d a p t a t i o n  s t r e s s t h e need t o know the d a r k a d a p t a t i o n c u r v e t o know t h e i n t e n s i t y de-t e r m i n i n g s c o t o p i c ^ m e s o p i c & p h o t o p i c . These f u n c t i o n s a r e i m p o r t a n t f o r p e r i m e t r y & a c u i t y t e s t s  glaucomas can have h i g h p o i n t , o r h i g h and l a t e p o i n t , o r n o r m a l p o i n t c o n t ' d ro H P a p e r C l i n i c a l C a t e g o r i e s Pre-adap t a t i o n i n t e n s i t y , d u r a t i o n t e s t l o c a t i o n Ourgaud & n o r m a l s , glaucoma E t i e n n e , ( i . e . , a c u i t y n o r m a l ; c i t i n g s m a l l d i s c c h a n g e s ) , Ourgaud & " s u s p e c t s " ( i . e . , A u b e r t , mate o f a glaucoma-1958 t o u s eye, p o s i t i v e h e r e d i t y , pseudo-e x f o l i a t i o n , no h i g h IOP, f i e l d changes OR h i g h IOP ^ p o s i t i v e w a t e r t e s t OR l i m i t e d o u t f l o w ) no t s p e c i f i e d V a l u e s o f n o r m a l Dependent d a r k a d a p t a -& glaucoma depen- t i o n v a r i a b l e s : c o r r e -dent d a r k a d a p t a - l a t i o n s w i t h c l i n i c a l t i o n v a r i a b l e s v a r i a b l e s compared  A l l o f t h e glaucoma c u r v e i s r a i s e d \ S u s p e c t s d e p a r t f r o m n o r m a l s o n l y a f t e r 20 m i n . , but t h e e f -f e c t i s i n s i g n i f i c a n t d a r k a d a p t a t i o n c o m p a r i s o n s between a poor o u t f l o w , s u s p e c t g r o u p , & n o r m a l s i s s i g n i f i c a n t , b u t t h e h i g h IOP s u s p e c t s & t h e p e r i m e t r i c s u s p e c t s don't d e p a r t f r o m n o r m a l s s i g -n i f i c a n t l y . ro 215 APPENDIX B A Technique for Re-Palntlng Photometric Spheres This is a brief account of a method found to be reasonably ade-quate. The technique described was worked out as other ones failed. I. The Paint An inexpensive mixture of barium sulfate (reagent grade) was used, combined with carboxymethyl-cellulose (CMC) as suggested by Middleton and Sanders^ F i r s t , a solution of the CMC ester in water must be prepared. A 2.5% solution (by weight) i s the most manageable for the quantities we were working with. Again, according to Middleton and Saunders' instruc-tions for a photometric white paint with low gloss, high reflectance, and good durability, barium sulfate and a quantity of CMC solution were mea-sured out so that the proportion (by weight) was 1000 Barium Sulfate: 1 CMC ester (Not solution), taking into account, of course, that there are 2.5 g of CMC ester i n 100 ml. of water (not solution). Using a mortar and pestle, the measured solution was worked into the whole quantity of barium sulfate, drop by drop. Then the mixture was thinned gradually by working in additional water. It's important to work every addition in as thorough-ly as possible. Water was added unt i l the paint was about as thick as medium cream, and i t was stored i n a covered jar this way. This paint w i l l adhere to, among other things, metal, painted surfaces, and opal glass. II. Painting the Sphere The paint should be thinned with, water to the consistency of light 216 cream. The only way to apply It successfully i s by spraying i t on. A Bink's 59-10002 "B" a i r brush with a Bink's 34-2020 a i r compressor (30 psi) accomplished this. Occasionally the opening the paint is delivered through w i l l clog and i t i s necessary to adjust the size of the opening as painting progresses. It i s best to apply several coats; drying time between coats can be shortened by directing the heat of a desk lamp on the surface. If wet spots appear or puddles form, painting should be stopped and the coat should be allowed to dry. Don't touch a wet surface as i t w i l l smear and make subsequent coats uneven. Surfaces painted with the barium sulfate mixture cannot, of course, be washed. Rather, a new coat should be applied, or the old paint should be removed with water, and the surface painted again from the beginning. It helps to prime surfaces that are very different from white to begin with; use any white paint that w i l l adhere. The dry barium sulfate paint i s moderately resistant to abrasion, but not very resistant to scratching. Middleton, W.E. Knowles and Sanders, C.L., An improved sphere paint, I I I . Eng., 48: 5, 1953, pp. 254-256. 

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