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Simulated lens , macular and illumination changes and their effects on colour vision Tansley , Brian Warren 1972

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CI SIMULATED LENS- MACULAR AND ILLUMINATION CHANGES AND THEIR EFFECTS ON COLOUR VISION by BRIAN WARREN TANSLEY B.A., U n i v e r s i t y o f B r i t i s h Columbia, 1971 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n the Department of Psychology We accept t h i s t h e s i s as conforming to the re q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA September, 1972 In presenting t h i s thesis in p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that, the Library shall make it f r e e l y a v a i l a b l e for reference and study. I further agree that permission for extensive copying of t h i s thesis; for scholarly purposes may be granted by the Head of my Department or r by his representatives. It is understood that copying or p u b l i c a t i o n of t h i s thesis for f i n a n c i a l gain shall not be allowed without my written permission. Department of The University of B r i t i s h Columbia Vancouver 8, Canada i ABSTRACT Two experiments i n v e s t i g a t e d the e f f e c t s of p r e - r e c e p t -o r a l • a b s o r p t i o n and l e v e l s o f i l l u m i n a t i o n on c o l o u r v i s i o n . S imulation f i l t e r s approximating l e n s and macular pigment changes were constructed on the b a s i s of o r e v i o u s i n v e s t i -g a t i o n s . Experiment I i n v e s t i g a t e d the e f f e c t s o f these f i l t e r s on young, normal subject performance. S h i f t s were found i n the d i r e c t i o n of ageing p o p u l a t i o n s but not as great as i s r e q u i r e d . Experiment I I i n v e s t i g a t e d the a d d i t i o n a l e f f e c t o f r e d u c t i o n s i n i l l u m i n a t i o n . The two experimental manipulations together account f o r s e n i l e decreases i n d i s c r i m i n a t i o n at s l i g h t l y h i gher l e v e l s than p r e v i o u s l y r e p o r t e d . i i TABLE OF CONTENTS Page A b s t r a c t . . . . . . . . • » . . . . • . . « . . . . . , . . . . . . . » ! L i s t o f Tables i i i L i s t o f F i g u r e s i v Acknowledgments v i I n t r o d u c t i o n . . . . 1 Experiment I 40 Apparatus 40 Method 52 Re s u i t s . . . . . 5 4 Experiment I I 67 M o d i f i c a t i o n s o f the P i c k f o r d - N i c h o l s o n Anomaloscope 6$ Method 73 R e s u l t s 7o D i s c u s s i o n . .o# B i b l i o g r a p h y 95 Appendix ...<> 104 i i i LIST OF TABLES Table * Page 1. V a r i a t i o n s i n Pigment Density f o r D i f f e r e n t Groups • 14 2. V a r i a t i o n s i n Pigment Density f o r D i f f e r e n t Groups ... . ..15 3<> B r i g h t n e s s Values of the Least and Most Dense Experimental Simulation F i l t e r s 51 4 . S i m u l a t i o n C o n d i t i o n s f o r Experiment 1 . , . . 5 1 5. Anomaloscope Mid - P o i n t s and Standard Devia-t i o n s f o r the C o n t r o l C o n d i t i o n s . * 57 6. Anomaloscope Mid - P o i n t s and Standard D e v i a t i o n s f o r S i n g l e F i l t e r C o n d i t i o n s . . .58" 7 . Anomaloscope Mid-Points and Standard D e v i -a t i o n s f o r T w o - f i l t e r C o n d i t i o n s 59 6*. Means and Standard D e v i a t i o n s f o r 100 hue t e s t (By Box) 64 9 . Anomaloscope Mid-Points and Standard D e v i a t i o n s f o r 10X Luminance of Exp. 1 . . . . . 8 2 10. Means and Standard D e v i a t i o n s f o r 100-hue Test 83 i v LIST OF FIGURES FIGURE Page 1, Spectral Absorption of Human Lenses as a Function of age........ . . • 4 2. Estimates of Scatter i n the Human Eye as a Function of age . •. . . . 6 3a Wald's (1945) Estimate of the "macular pigment" . 10 3b Ishak's (1953) Estimate of the "macular pigment .11 3c Ruddock's (I960 Estimate of the "macular pigment" 12 3d Bone and Sparrock's (1971) 3 d e n s i t i e s of estimated "macular pigment" . . . . . . . 1 6 3e Bone and Sparrock's (1971) Average estimate of the "macular pigment" ...............17 3f Estimate of the macular pigment by Naylor and Stanworth • 21 U Experimental simulation f i l t e r s used by Lakowski (1962) 30 5. V e r r i e s t (1963) Experimental f i l t e r s . . .33 6. Mean P a r t i a l Error Score Plots . . . . 34 7. A s p i n a l l ' s (1968) Experimental simulated Macular Pigment f i l t e r s (Xanthophyll i n Chloroform) 37 8. Wald's macularpigment and I l f o r d f i l t e r s Lakowski (1962) and Wald's 'macular pigment' estimates of Said and V/eale's lens estimates f o r 4 ages .39 9 . Absorption Ch a r a c t e r i s t i c s of the Simulated Lens F i l t e r s . . . . . . . . . 4 3 V F I G U R E P a g e 10. A b s o r p t i o n C h a r a c t e r i s t i c s o f t h e S i m u l a t e d m a c u l a r p i g m e n t f i l t e r s 46 11a A b s o r p t i o n C h a r a c t e r i s t i c s o f M a c u l a r S i m u l a t i o n F i l t e r ' A ' and E x p e r i m e n t a l l e n s v a l u e s . . . . . . . 4 7 l i b A b s o r p t i o n C h a r a c t e r i s t i c s o f m a c u l a r S i m u l a t i o n f i l t e r ' B » a n d e x p e r i m e n t a l l e n s v a l u e s . . . . . . . . 4 3 11c A b s o r p t i o n C h a r a c t e r i s t i c s o f M a c u l a r S i m u l a t i o n f i l t e r • C * a n d e x p e r i m e n t a l l e n s v a l u e s • • . . . . . . . 4 9 l i d A b s o r p t i o n C h a r a c t e r i s t i c s o f M a c u l a r S i m u l a t i o n f i l t e r "d " a n d e x p e r i m e n t a l l e n s v a l u e s . . . . . . . . 5 0 12a A p e r t u r e l u m i n a n c e a s a f u n c t i o n o f s h u t t e r s e t t i n g 71 12b A p e r t u r e l u m i n a n c e i s a f u n c t i o n o f s h u t t e r s e t t i n g 72 I 13. S p e c t r a l c h a r a c t e r i s t i c s o f A n o m a l o s c o p e f i l t e r s ( M o d e l I ) at a p e r t u r e o o . . » 7 4 14a P a n e l D-15 Mean S c o r e s 76 14b P a n e l D-15 Mean S c o r e s 77 15a 100-hue P r o f i l e s 79 15b n n n £0 15c n n n g l 16a F r e q u e n c y H i s t o g r a m s f o r C o n f u s i o n E r r o r s o n t h e AO H - R - R t e s t 86 16b F r e q u e n c y H i s t o g r a m s f o r C o n f u s i o n E r r o r s o n t h e D v o r i n e T e s t 37 17. 100 hue p r o f i l e f o r 4 m u t u a l l y i n c r e a s i n g p a i r s o f s i m u l a t i o n f i l t e r s 100 l u x . . . . . . 9 3 vi ACKNOWLEDGMENTS The author would l i k e to express h i s g r a t i t u d e to many people who co n t r i b u t e d t o the development o f t h i s t h e s i s : K e i t h O l i v e r S h e i l a Campbell Susan Bridge The observers who p a t i e n t l y sat through hours of t e s t i n g . F i n a l l y , the author would l i k e to thank Dr. R. Lakowski f o r h i s c o n s t r u c t i v e encouragement and c r e a t i v i t y . - 1 -INTRODUCTION The aim o f the present i n v e s t i g a t i o n i s to p h y s i c a l l y and extraneously simulate changes i n the absorption -c h a r a c t e r i s t i c s o f the human c r y s t a l l i n e l ens and macula l u t e a and to look at the e f f e c t s o f p r e r e c e p t o r a l absorption on h u e - d i s c r i m i n a t i o n , c o l o r matching and p o s s i b l y , c o l o r confusion. In a d d i t i o n , the e f f e c t of red u c t i o n s and incr e a s e s i n i l l u m i n a t i o n on v a r i o u s t a s k s purported to measure the aforementioned c o l o r v i s i o n parameters w i l l be examined i n an attempt to estimate the reasons f o r decreased c o l o r d i s c r i m i n a t i o n i n the ageing p o p u l a t i o n . In order f o r the r a d i a t i o n man c a l l s l i g h t t o be recognized as such i t must f i r s t t r a n s v e r s e the o c u l a r media and r e t i n a l l a t t i c e to e x c i t e the end-organs o r photo-r e c e p t o r s . From the a i r - c o r n e a l i n t e r f a c e to i t s u l t i m a t e absorption and t r a n s d u c t i o n i n t o nerve impulses, l i g h t i s r e f r a c t e d and attenuated. The l a t t e r , a t t e n u a t i o n , can be achieved through the absorption o f l i g h t by matter o r the s c a t t e r i n g o f l i g h t i n d i r e c t i o n s o t h e r than t h a t o f the o r i g i n a l i n c i d e n t ray. T h i s a t t e n u a t i o n can be, i n terms of wave-length, s e l e c t i v e or n o n - s e l e c t i v e depending upon the c h a r a c t e r i s t i c s of the media which the ray passes through. In the human eye, the two most wid e l y studied o f these media are the c r y s t a l l i n e l e n s and the macula l u t e a region of the 1 c e n t r a l r e t i n a . CRYSTALLINE LENS The t h i r d o p t i c media which l i g h t must pass through on i t s way to the r e t i n a l photoreceptors i s the c r y s t a l l i n e l e n s . In the normal eye the lens i s a biconvex, transparent n e r v e l e s s and v e s s e l - f r e e s t r u c t u r e which i s composed of 60-70$ water, 6fo f a t and r e l a t i v e l y more p r o t e i n than any other t i s s u e (Brown, 1965). The l e n s c o n t a i n s a s l i g h t l y y e l l o w pigment which has t e n t a t i v e l y been i d e n t i f i e d by McEwan (1959) t o be a urochrome l i k e t h a t i s o l a t e d from u r i n e and not melanin as p r e v i o u s l y thought. S p e c t r a l t r a n s m i s s i o n c h a r a c t e r i s t i c s f o r the human o c u l a r media were f i r s t attempted by Aschkinass i n 1895.^ H i s methods were r e p o r t e d l y i n a c c u r a t e and as w e l l the v i s i b l e spectrum was entered only to the extent o f 670 nanometers (nm), i n the f a r r e d . H i s co n c l u s i o n was t h a t the o c u l a r media resembled water i n terms of i t s a b s o r p t i o n c h a r a c t e r i s t i c s . Up u n t i l about 1938, t h i s was the general consensus when Ludvigh and 1. Boynton and Clarke (1964) p o i n t out t h a t the co r n e a l s t r u c t u r e accounts f o r a reasonably l a r g e p r o p o r t i o n o f s c a t t e r . 2. McEwan (1959, pp 146) s t a t e s t h a t the urochrome substan found i n the l e n s i s probably a n o n - s n e c i f i c degradation product o f p r o t e i n . This f i n d i n g i s c o n s i s t e n t w i t h the f i n d i n g t h a t the l e n s s t r u c t u r e i s p r o t e i n r i c h . 3. As c i t e d by Ludvigh and McCarthy (1938") -3-McCarthy (1938) p u b l i s h e d estimates of the o c u l a r media and reported t h a t " i t i s the l e n s which accounts f o r the major p a r t of the s e l e c t i v e absorption of the eye i n the v i s i b l e spectrum".'4' U n f o r t u n a t e l y , Ludvigh and McCarthy d i d not p u b l i s h r e s u l t s on the i n d i v i d u a l components of the oc u l a r media and i t was not u n t i l 1945 t h a t Wald pub l i s h e d absorption c h a r a c t e r i s t i c s f o r human l e n s e s . Weale (1954) o b j e c t s t o V/ald's (1945) f i n d i n g s on the b a s i s t h a t the lenses may have reached an " u n p h y s i o l o g i c a l degree o f clo u d i n e s s " ^ by the time the measurements were made. Weale (1954) r e p o r t s l e n t i c u l a r s p e c t r a l absorption curves which were based on two melanotomous eyes and t h e r e f o r e h i s data may have been u n r e l i a b l e . ^ * The f i r s t s u c c e s s f u l and compre-hensive measurements made i n s i t u on a cross s e c t i o n o f age-groups was made by Said and Weale (1959). Using a technique by which comparisons o f the s m a l l but measurable amounts of l i g h t r e f l e c t e d at the v a r i o u s media i n t e r f a c e s , otherwise known as P u r k i n j e images, the authors d e r i v e d l e n t i c u l a r s p e c t r a l absorption curves at s i x ages. T h e i r r e s u l t s are shown i n Figu r e 1. McEwan (1959) suggests t h a t the pigment may i n c r e a s e i n concentration w i t h age. M e l l e r i o (1971) 4 . i b i d , pp 48 5. Said and Weale (1959) 6. Up u n t i l about 1950, a l l measurements were made i n s i t u on e x t i r p a t e d lenses. Said and Weale (1959) report t h a t F. Salomon (1950) made some of the f i r s t i n v i v o measure-ments. - 4 -WAVELENGTH (nm) F I G U T G 1 S p e c t r a l Absorption of Human Lenses as a f u n c t i o n of age. from Said and Weale (1959) . - 5 -suggests the a t t e n u a t i o n o f v i s i b l e l i g h t through the l e n s 7 by a b s o r p t i o n and s c a t t e r i s due to a " h y p o t h e t i c a l ab sorb ing p igment" , but because the l i g h t l o s s i n the c e n t r a l 7-8 mm r e g i o n remains constant between ages 20 and 60, the s e n i l e y e l l o w i n g e f f e c t i s seen as due to i n c r e a s e s i n l e n s t h i c k n e s s . A l though i n genera l agreement w i t h t h i s c o n c l u s i o n Weale (1961b) p o i n t s out t h a t t h i s f i n d i n g may be a p p l i c a b l e t o young and middle aged l e n s e s o n l y and n o t o l d l ense s -which might have accumulated more dense pigment i n the n u c l e u s . Ruddock (1964) s t a t e s t h a t " i t appears t h a t the l e n s a g e i n g , o c c u r r i n g w i t h o u t any accompanying changes i n the r e c e p t o r a l re sponse , can s u c c e s s f u l l y p r e d i c t the e f f e c t o f age upon g c o l o r v i s i o n " . He i n d i c a t e s t h a t the s c a t t e r i n g e f f e c t i n -creases as a f u n c t i o n o f age and t h a t t h i s e f f e c t i s a n a l -ogous to the da ta o b t a i n e d f o r c o l o r matching d a t a . Ruddock (1964) f u r t h e r argues the s c a t t e r i n g i n c r e a s e w i t h age would he lp t o account f o r the l o s s o f v i s u a l a c u i t y w i t h age as w e l l . Increa se s i n s c a t t e r due t o age e f f e c t s are presented 9 i n F i g u r e 2 . From the two p r e c e d i n g f i g u r e s i t can c l e a r l y be seen t h a t the Lens pigment a c t s l i k e a c o l o r f i l t e r , ( i . e . 7. When minute p a r t i c l e s i n a medium r e f l e c t l i g h t i n a p a r t i c u l a r manner the l i g h t i s s a i d to be s c a t t e r e d . The Short wavelengths tend to produce more s c a t t e r than do l o n g e r ones , (see R i g g s , 1965» pp 24) M e l l e r i o does not s t a t e the r e l a t i v e c o n t r i b u t i o n s o f a b s o r p t i o n and s c a t t e r t o the a t t e n u a t i o n o f l i g h t . 8 . Ruddock (1964) pp . 191 9o i b i d . pp . 137 ( i s an adaoted f i g u r e ) -6-WAVELEN6TH (nm) Figure 2 E s t i m a t e s of S c a t t e r i n the Human Eye as a Function o f Age. adapted from Ruddock (1964) - 7 -the c o l o r changes and the transparency changes at d i f f e r e n t wavelengths) and l i k e a s c a t t e r i n g f i l t e r of the R a y l e i g h - -type, a t t e n u a t i n g the short-wave end of the s p e c t r u m . ^ Ruddock (1972) r e p o r t s that according t o Vos and Boogaard (1963) l i g h t s c a t t e r i n g 'centers' are not un i f o r m l y d i s t r i -buted throughout the le n s volume and t h e r e f o r e s c a t t e r l o s s e s cannot be i n t e r p r e t e d i n terms of a u n i f o r m l y d i s t r i b u t e d p i g -ment. (Weale, 1961 (b)) THE MACULAR PIGMENT The macula l u t e a i s an area around and i n c l u d i n g the fovea c e n t r a l i s o f about 3-5 mm i n diameter. According t o Ishak (1952) the macula l u t e a was f i r s t observed by B u z z i i n 1682 and independently again by Soemmering i n 1795. Soemmer-r i n g i s reported to have observed the "macula pigment""^ (acco r d i n g to Ruddock (1964)) and G u l l strand (1906) i s reported (by the same author) t o have i d e n t i f i e d the pigment as a caroteno l d and, f u r t h e r , stated t h a t i t was a p o s t -mortem e f f e c t . H a r t r i d g e , (1950) held the "post-mortem e f f e c t " viewpoint as w e l l . Although some w r i t e r s do not f u l l y accept i t s e x i s t e n c e i n v i v o (Trezona, 1970) there i s a m a j o r i t y o f 10. Cooper and Robson (1969) p o i n t to the p o s s i b i l i t y o f a second u l t r a - v i o l e t - a b s o r b i n g pigment o c c u r r i n g i n o l d e r l e n s e s which would add t o the general 'yellowness' o f the l e n s c o l o r . 1 1 . This may be a m i s i n t e r p r e t a t i o n as a r e s u l t o f ambig-u i t i e s i n the t h e s i s t e x t . Soemmerring may have, i n f a c t , only observed the macula l u t e a i n v i t r o as the ophthalmoscope was invented by Helmholtz at a l a t e r date. - 8 -r e p o r t s which do c o n f i r m i t s e x i s t e n c e i n the l i v i n g human eye . X a n t h o p h y l l ' s a s s o c i a t i o n w i t h the o x i d a t i o n process i n p l a n t s p l u s the b e l i e f t h a t the v a s c u l a r r e t i n a l system at the f o v e a l r eg ion appeared inadequate i n and o f i t s e l f , prompted D a r t n a l l and Thompson (1949) t o i m p l i c a t e the macular pigment i n an oxygen- t ranspor t system to the f o v e a l p h o t o r e c e p t o r s . Denton and P i renne (1950) and Wald (1967) suggests t h a t the macular pigment i s an adapt ive mechanism which serves to min imize chromat ic a b e r r a t i o n i n the f o v e a l r e g i o n ( r e g i o n o f the h ighes t a c u i t y ) by ab sorb ing much o f the short wavelength l i g h t . A l though the l e n s absorbs shor t wavelengths as w e l l , the macular pigment ' peaks ' i n the 460 nm range whereas the l e n t i c u l a r pigment absorbs max imal ly 12 c l o s e r to 400 nm. B a s i c a l l y , two major types o f e v i d e n c e , a l b e i t i n d i r e c t , support the e x i s t e n c e o f the macular pigment i n v i v o . (a) The comparison o f f o v e a l and p a r a - f o v e a l s p e c t r a l s e n s i t i v i t i e s , and; (b) e n t o p t i c c o l o r p e r c e p t i o n o f M a x w e l l ' s Spot and the H a i d i n g e r B rushes . 12 . Wyszeck i and S t i l e s (1967) use 403 nm as t h e i r r e f e rence p o i n t f o r the l e n s a b s o r p t i o n and 455 nm f o r the macular pigment a b s o r p t i o n . -9-A. COMPARISON OF FOVEAL AND PARAFOVEAL SPECTRAL SENSITIVITY Wald ( 1 9 4 5 ) e x t r a c t e d the pigment from a small number of human maculas and subsequently i d e n t i f i e d i t as "a hydroxy-carotenoid or x a n t h o p h y l l , i n a l l p r o b a b i l i t y l u t e i n or l e a f x a n t h o p h y l l i t s e l f " . ' V/ald f u r t h e r obtained p s y c h o p h y s i c a l data based on comparisons of f o v e a l and p a r a f o v e a l 8 ° s p e c t r a l s e n s i t i v i t y and adjusted the o p t i c a l d e n s i t y o f the macular x a n t h o p h y l l to f i t t h i s d a t a . ^ The estimate of the macular pigment from both these f i n d i n g s i s presented i n Figure 3(a). Ishak ( 1 9 5 2 ) i n v e s t i g a t e d the macular pigment d e n s i t i e s o f 1 5 Egyptian s u b j e c t s and noted that t h e i r average values were higher than those reported by B r i t i s h , American and German observers. H i s r e s u l t s and the i n v e s t i g a t i o n s o f others reported by him are present i n Figure 3(b). Ruddock ( 1 9 6 3 ) published estimated macular pigment d e n s i t i e s of two obser-v e r s . H i s estimate i s based on h i s own v i s u a l system and i s reproduced i n Figure 3(c), I t i s t o be noted t h a t h i s second observer has almost no macular pigment according to the data presented, yet (Ruddock 1972 (b)) fundus r e f l e c t o -metry data estimates the d e n s i t i e s t o be equal i n both 1 3 . Wald ( 1 9 4 5 ) P P . 657 1 4 . Wald ( 1 9 4 9 ) t r i e d t o i n t e r p r e t the increased p e r i p h e r a l s e n s i t i v i t y to the blue-end of the spectrum as the absence of macular pigmentation. Weale ( 1 9 5 3 ) suggests however, t h a t the noted increase i n b l u e - s e n s i t i v i t y may be due to improvements i n the s e n s i t i v i t y of the p e r i p h e r a l photo-receptors. -10 • ViSuftL E s r i m f i T E p "tvxiaUao XHtiikflnyll 0.9 as o.7 0.6 0 5 0.3 03 0.1 o Coo 350 45c $00 £50 WAVELENGTH (nm) niirP 3 fl V7ald's (1945) Estimat y u i ^ v ^ u n m a c u l a r pigment". e of the - 1 1 -WAVELENGTH (nm) UTG 3 b Ishak's (1953) Estimate of the •macular pigment'* - 1 2 -FJQUre 3C Ruddock's (1964) Estimate of J the 'macular pigment'. observers. Bone and Soarrock (1971) report a r a t h e r compre-hensive study which i n c l u d e macular pigment estimates of 49 observers. T h e i r comparisons are inc l u d e d i n Figu r e 3(d -i e ) . Groups contrasted i n the l a t t e r study i n c l u d e d those o f Table I . From t h e i r i n v e s t i g a t i o n i t appears as i f d a r k l y pigmented peoples tend to have s l i g h t l y more macular pigment 15 than do l i g h t l y pigmented people. B. ENTOPTIC COLOR PERCEPTION OF MAXWELL'S SPOT AND THE HAIDINGER BRUSHES. The second major method of e s t i m a t i n g the macular p i g -ment i s w i t h the use o f e n t o p t i c phenomena. I f f o r example a subject views a uniform f i e l d (which i s i l l u m i n a t e d by a continuous source) a l t e r n a t e l y through a n o n - s e l e c t i v e grey f i l t e r and a purple g e l a t i n f i l t e r ( t r a n s m i t t i n g o n l y near the short-wave ( b l u e - v i o l e t ) and the long-wave (red) ends o f the spectrum) he w i l l most l i k e l y n o t i c e a spot subtending about 3-4° about the f i x a t i o n p o i n t o f resp e c t . T h i s spot was f i r s t d e s c r i b e d by Maxwell who i n t e r p r e t e d i t as due to decreased e f f e c t i v e n e s s of blue l i g h t i n s t i m u l a t i n g the cones o f the f o v e a l region because i f i t s absorption by the macular pigment. 15. One notable exception as seen i n Table I i s o f the red -h a i r e d versus non-red-haired comparison. The named authors are r e p o r t e d l y i n v e s t i g a t i n g t h i s f i n d i n g f u r t h e r because of the small number of s u b j e c t s . -14-Table I V a r i a t i o n s i n Pigment Density-Wavelength Eas t I n d i a n 400 0.49 410 0 .52 420 0.53 430 0.59 440 0.63 450 0.68 460 0 .69 470 0 .64 480 0 .56 490 0 .46 500 0 .36 510 0 .29 520 0 .21 530 0 .16 540 0.12 550 0.08 f o r D i f f e r e n t Groups (from Bone and Sparrock , 1971) Non-East Red h a i r e d Non-red I n d i a n h a i r e d 0.35 0 .54 0 .34 0.38 0.57 0 .36 0 .40 0.62 0.39 0 .44 0 .66 0.43 0 .43 0.71 0 .46 0 .52 0.74 0 .50 0 .52 0.73 0 .51 0.49 0.68 0.48 0 .44 0.63 0.43 0 .36 0 .52 0.35 0.28 0 .41 0 .27 0 .22 0 .32 0.21 0 .16 0 .24 0 .16 0.13 0.19 0.12 0.10 0.14 0.09 0 .07 0.09 0 .07 - 1 5 -Table I V a r i a t i o n s i n Pigment D e n s i t y f o r D i f f e r e n t Groups (from Bone and Soarrocl '1971) ive length Age Over Age Under (nm) 30 22 400 0.34 0 .36 410 0.37 0.38 420 0 .41 0 .41 430 0.43 0 .44 440 0.48 0.48 450 0.52 0.51 460 0.53 0.52 470 0.49 0.48 480 0 .45 0.43 490 0.35 0 .36 500 0.27 0.28 510 0.22 0.22 520 0 .16 0 .17 530 0.12 0 .14 540 0.08 0 .11 550 0 .06 0.08 - 1 6 -Figure 3d Bone and Sparrock'.y( 1971) 3 d e n s i t i e s of estimated 'macular pigment'. -17-loo _ 5&? WAVELENGTH (nm) Figure 3 e Bone and Spar-rock's (1971) Average estimate of the 'macular pigment'. -18-Judd (1953) reported: According to the assumed three-components theory the macular pigment should be v i s i b l e e n t o p t i c a l l y by means of the w a l l s purple f i l t e r and a non-rselective grey f i l t e r of about one percent t ransmittance used a l t e r n a t e l y even though there i s no d i f f e r e n c e between macular and extra-macular r e c e p t o r s e i t h e r as to Dooulation d e n s i t y , as suggested by W a l l s , o r as to s p e c t r a l s e n s i t i v i t y apart from d i f f e r e n c e introduced by the macular pigment i t s e l f . . . and: To e x p l a i n Maxwell's Spot, there i s no need to assume the existence of macular r e c e p t o r s having s p e c t r a l s e n s i t i v i t i e s or p o p u l a t i o n d e n s i t i e s which are d i f f e r e n t from those o f the extra-macular r e c e p t o r s . On the other hand, t h i s a n a l y s i s leaves open the p o s s i b i l i t y t h a t such macular r e c e p t o r s do e x i s t and c o n t r i b u t e to Maxwell's S p o t . 1 " Although Judd d i d h i s a n a l y s i s on the standard observer (which i s based on r e a l observers but not r e a l i t s e l f ) h i s r e s u l t s i n d i c a t e t h a t the Maxwellian spot i s an e n t o p t i c p e r c e p t i o n of the macular p i g m e n t . ^ Judd used Wald's (1945) estimates of the macular pigment f o r h i s a n a l y s i s and d i d not estimate a d e n s i t y w i t h r e a l o r t h e o r e t i c a l observers. Ruddock (1965) p o i n t s out t h a t : the Maxwell-spot e f f e c t i s a s s o c i a t e d w i t h wavelengths at which the macular pigment i s expected to absorb. I t i s not seen by observers who, from c o n s i d e r a t i o n of c o l o r matches i n the fovea and parafovea, would be c l a s s i f i e d as non-pigmented. When a plane p o l a r i z e r i s r o t a t e d before the observer's eye, the maxwell spot breaks up i n t o a form t y p i c a l of Haidinger's brushes. The brushes ... are s i m i l a r i n c o l o r t o the us u a l Maxwell spot, whereas the i n t e r v e n i n g space appears the same as the surrounding f i e l d . T h i s breakdown of c e n t r a l u n i f o r m i t y i n p o l a r i z e d l i g h t supports 16. Judd (1953) PP. 20 17. This i s a confirmation of Maxwell's own report according to Judd (1953). -19-the t h e o r y t h a t the n o n u n i f o r m i t y i t s e l f , and hence the a s s o c i a t e d changes i n c o l o r match ing , i s due to l i g h t l o s s e s which occur p r i o r t o v i s u a l e x c i t a t i o n . The o b s e r v a t i o n a l s o l i n k s the Maxwel l - spot and H a i d i n g e r brush phenomena, 1 8 Trezona (1970) f e e l s t h a t the macular pigment i s not needed to e x p l a i n M a x w e l l ' s spot : L i g h t i s absorbed by the rods most e f f e c t i v e l y i n the b l u e -green , t h i s g i v e s a b l u e sensa t ion i n the p e r i p h e r y and the fovea appears y e l l o w s imultaneous c o n t r a s t . 1 " In f a c t T r e z o n a ' s argument extends to p r a c t i c a l l y a l l o f the evidence i n support o f the macular p igment . The H a i d i n g e r "b rushes " o r H a i d i n g e r e f f e c t was used to e s t imate the macular pigment ex tant i n human s u b j e c t s by D e V r i e s , Spoor and J i e l l d f ( 1 9 5 3 ) . However, they used a l a r g e r t e s t f i e l d 20 than c o n t a i n s the macular pigment and thus t h e i r r e s u l t s are open to c r i t i c i s m a l o n g these l i n e s . N a y l o r and S tan-worth (1954) used 1 ° f i e l d f o r s t i m u l a t i o n t o produce the ?1 e f f e c t . They c a l c u l a t e d t h e i r r e s u l t s ON THE PREMISE t h a t the macular pigment was r e s p o n s i b l e f o r the e f f e c t . They found t h a t , as opposed t o c a l c u l a t i n g i n f o r m a t i o n on the premise t h a t the o r i e n t a t i o n o f b l u e r e c e p t o r s was r e s p o n s i b l e , 22 the data best f i t the former i n t e r p r e t a t i o n . They concluded 18 . Ruddock (1965) p p . 1180 19 . Trezona (1970) p p . 330 20 . o r as an a l t e r n a t i v e hypothes i s would have i t , the o r i e n t a t i o n o f b l u e - r e c e o t o r s 2 1 . D e V r i e s e t . a l . (1953) d i s c u s s the reasoning f o r the H a i d i n g e r e f f e c t . 22 . In an e a r l i e r paper , Stanworth and N a y l o r (1950) s t a t e d t h a t the l a t t e r was the cause o f H a i d i n g e r * s e f f e c t . - 2 0 -t h a t the Haidinger e f f e c t was caused absorption of l i g h t by the o r i e n t e d macular pigment. T h e i r estimate of the o r i e n t e d pigment i s i n Figure 3 ( f ) . Naylor and Stanworth s t a t e tenuously t h a t t h e i r macular pigment curve corresponds w i t h t h a t o f Xanthophyll but th a t i t s p o s i t i v e i d e n t i f i c a t i o n cannot be considered c e r t a i n because of an a d d i t i o n a l maxi-mum absorption at 515 mm and anomalies i n Xanthophyll's peak absorption p o i n t w i t h d i f f e r e n t s o l v e n t s . 2 ^ The macular pigment has a l s o been i m p l i c a t e d i n the Haidinger brush e f f e c t by Sloan and Naquin (1955). Because o f the d i f f i c u l t y i n i n t e r p r e t i n g the r e s u l t s , Wyszecki arid Stiles, (1967 ) and Ruddock (1972) have suggested l e s s weight be placed on estimates o f macular pigment d e n s i t y made by use o f the e n t o p t i c phenomena. INCREASES IN THE MACULAR PIGMENT DUE TO AGEING S t i l e s and Burch (1959) i n d i c a t e t h a t the macular pigment d e n s i t y i n c r e a s e s as a f u n c t i o n o f the age o f the observer. By n o t i n g observer v a r i a t i o n s i n the r e s u l t s o f t h e i r 10° c o l o r matching i n v e s t i g a t i o n a c o r r e l a t i o n w i t h age was found. Because not a l l of the variance could be accounted f o r i n l e n s pigmentation i n c r e a s e s as a f u n c t i o n o f age, they suggested t h a t the macular pigment might increase w i t h age 2 3 . According to my data on solvents f o r x a n t h o p h y l l , chloroform produces a peak at approximately 455 nra wh i l e other s o l v e n t s (such as ethanol 98$ and acetone) s h i f t t h i s peak as much as 10 nm. -21-o o Values of Lo^ &(frO?oA\oH<J- h Optical density <JT orie^W pi<jm»* Sao 9 -5QO WAVELENGTH (nm) F'lQUre 3f Estimate o f the macular pigment ^ by Naylo r and Stanworth (1954) -22 a l s o . Warburton (1953) came to a s i m i l a r c o n c l u s i o n based upon the v a r i a t i o n s i n the matches o f i l l u m i n a n t ' B ' (expressed as a c o l o r temperature) made by two groups o f o b s e r v e r s . The f i r s t grout) aged 16-25 years matched the s t i m u l u s c l o s e r to i l l u m i n a n t * C T whereas the second group aged 56-65 years matched the s t i m u l u s near i l l u m i n a n t ' A * . Warburton i n t e r p r e t e d t h i s d i f f e r e n c e i n terms o f i n c r e a s e s i n macular pigment d e n s i t y . Bone and S p a r r o c k ' s (1971) da ta i n d i c a t e a very s l i g h t upward t r e n d i n the over 30-under 22 age c o n t r a s t but do not i n c l u d e i n f o r m a t i o n w i t h re spec t to these two groups as to the t o t a l age d i f f e r e n t i a l s examined. Wright (1946) , Weale (1963) and Ruddock (1965) have found no s i g n i f i c a n t i n c r e a s e i n macular pigment d e n s i t y w i t h observer age. The l a t t e r i n v e s t i g a t o r found t h a t age changes i n c o l o r matching data correspond c l o s e l y to the c a l c u l a t e d changes i n LENS a b s o r p t i o n . Ruddock (1972) p o i n t s out t h a t the macular pigment cannot account f o r a l l o f the d i f f e r e n c e between the C . I . E , ^ 2 ° and 10° c o l o r matching f u n c t i o n s and t h e r e f o r e , some r e c e p t o r a l response d i f f e r e n c e s must be i n c l u d e d . COLOR VISION TESTING The measurement o f the so c a l l e d normal/abnormal dimen-24. Commission I n t e r n a t i o n a l e d ' E c l a i r a g e o therwise known as the I n t e r n a t i o n a l Commission on I l l u m i n a t i o n . - 2 3 -s i o n s o f c o l o r v i s i o n have taken t h r e e c h a r a c t e r i s t i c forms: (a) c o l o r matching (b) hue d i s c r i m i n a t i o n and (c) c o l o r * • 25 c o n f u s i o n . (a) COLOR MATCHING There are two g e n e r a l methods o f c o l o r match ing . F i r s t l y , a moveable set o f samples can be matched t o another f i x e d set which e x h i b i t a one-to-one correspondence. (An example o f t h i s type o f method can be seen i n the ISCC C o l o r A p t i t u d e t e s t (1953)). Secondly , tv/o c o l o r s can be matched f o r hue s a t u r a t i o n and b r i g h t n e s s even though they a re composed o f d i f f e r e n t s p e c t r a l c h a r a c t e r i s t i c . METAMERIC MATCHING makes use o f t h i s f a c t * . A d d i t i v e o r s u b t r a c t i v e m i x t u r e s o f l i g h t can be made t o match j u s t about any s p e c t r a l c o l o r , i n c l u d i n g non s p e c t r a l p u r p l e s . A d d i t i v e metameric matching f o r c o l o r v i s i o n t e s t i n g can be ach ieved by the use o f a s imple a d d i t -26 i v e c o l o r i m e t e r known as an anomaloscope, w h i l e s u b t r a c t i v e metameric matching c.^n be achieved by the use o f a s u b t r a c t i v e 27 c o l o r i m e t e r such as the t i n t o m e t e r . The most common meta-2 5 . The l a s t form can be seen as an attempt to separate the human p o p u l a t i o n i n t o two f i r s t l y , two groups ; normal and d e f e c t i v e c o l o r v i s i o n , and f u r t h e r , t h i s l a s t group i n t o subgroups a c c o r d i n g to the c o l o r confus ions which they e x h i b i t . 26 . As a p a r t i c u l a r make and model o f t h i s ins t rument i s used i n the present i n v e s t i g a t i o n s , i t w i l l be d i s c u s s e d l a t e r . 27. The Lovibond S c h o f i e l d T intometer i s a s u b t r a c t i v e v i s u a l c o l o r i m e t e r which i s i n wide us i n i n d u s t r y f o r s p e c i f i c -a t i o n o f c o l o r . I t r e q u i r e s a f a i r l y s p e c i a l i z e d observer and proper methodology to m a i n t a i n c o n s i s t e n c y . - 2 4 -meric i n use f o r d i a g n o s i s of c o l o r v i s i o n d e f e c t i v e s and research i n t o c o l o r v i s i o n parameters i n g e n e r a l , i s the 28 R a y l e i g h match. By the a d d i t i v e mixture of red and green l i g h t one can produce a y e l l o w l i g h t which can be matched to another "pure" y e l l o w l i g h t . I f the two " y e l l o w s " match to a p a r t i c u l a r observer, the two are de f i n e d as a metameric p a i r . Now i n the normal p o p u l a t i o n there i s a range of r a t i o s ( i . e . amount of red to amount o f green) t h a t w i l l produce a y e l l o w which i s accepted as matching the pure y e l l o w . Extreme increa s e s o r extreme decreases i n t h i s r a t i o are stimulus parameters which h e l p f u l i n d e f i n i n g and d i a g -n o s i n g red-green c o l o r d e f e c t i v e observers. As w e l l as the Ra y l e i g h equation, o t h e r metameric matches are p r e s e n t l y employed i n re s e a r c h , n o t a b l y the yellow-blue equation and the blue-green or v i o l e t / b l u e - g r e e n equation. Lakowski (1971) p o i n t s out t h a t any number o f other equations could be used. Presumably, the R a y l e i g h , y e l l o w - b l u e and blue-green equations are u s e f u l i n determining the no r m a l i t y / a b n o r m a l i t y o f observers who f a l l i n t o the h i s t o r i c a l l y d e f i n e d c o l o r defect c l a s s i f i c a t i o n s . (b) COLOR DISCRIMINATION As opposed to matching o f c o l o r s , c o l o r d i s c r i m i n a t i o n r e q u i r e s the observer to note the emphasis o f d i f f e r e n c e s and 2 8 . Named a f t e r Lord R a y l e i g h noted E n g l i s h p h y s i c i s t i n the 19th Century.. -25-n o t j u s t s i m i l a r i t i e s . Two b a s i c methods a r e e m o l o y e d a t p r e s e n t . W a v e l e n g t h d i s c r i m i n a t i o n i n v o l v i n g s p e c t r a l c o l o r i s g e n e r a l l y c a r r i e d o u t w i t h t h e u s e o f s e v e r a l raonochrora-a t o r s o r d o u b l e m o n o c h r o m a t o r s w h i c h p r e s e n t a c o m p a r i s o n f o r t h e o b s e r v e r . In much t h e same way a s t h e a n o m a l o s c o p e i s u s e d , t h e o b s e r v e r i s r e q u i r e d t o n o t e s i m i l a r i t i e s and d i f f e r e n c e s i n t h e two s t i m u l i p r e s e n t e d . The d a t a h o w e v e r , i s u s u a l l y i n t e r p r e t e d i n t e r m s o f j u s t n o t i c e a b l e d i f f e r e n c e s i n c o l o r o r a s a d i f f e r e n c e t h r e s h o l d f o r c o l o r p l o t t e d a s a f u n c t i o n o f w a v e l e n g t h . A n o t h e r method o f d e t e r m i n i n g c o l o r d i s c r i m i n a t i o n p a r a m e t e r s i s t h e u s e o f t h e F a r n s w o r t h - M u n s e l l 100-hue t e s t . The t e s t i s composed o f 85 m o v e a b l e c a p s , e a c h c o n t a i n i n g a s e p a r a t e M u n s e l l c o l o r . The t e s t i s d i v i d e d i n t o f o u r b o x e s o r s e r i e s e a c h c o n t a i n i n g a b o u t 21 c a p s . T h e r e a r e two f i x e d c a p s i n e a c h b o x w h i c h r e p r e s e n t t h e e n d s o f t h e s o - c a l l e d c o n t i n i u m o f c o l o r s c o n t a i n e d i n t h e b o x . I n e a c h b o x t h e c a p s can be a r r a n g e d i n a CORRECT ( p e r f e c t ) o r d e r i n w h i c h c a s e t h e b o x s c o r e = 0 , The d e g r e e t o w h i c h t h e c a p s a r e d i s p l a c e d o u t o f t h i s c o r r e c t o r d e r i n c r e a s e s t h e s c o r e r e c e i v e d , A u s e f u l p a r t o f t h e s c o r i n g p r o c e d u r e o f t h i s t e s t i s t h a t s c o r e o f e a c h cap can be g r a p h e d i n a p o l a r c o n f i g u r a t i o n . The r e s u l t a n t f i g u r e can be g l a n c e d a t by an e x p e r i e n c e d t e s t e r and t h e d e g r e e o f n o r m a l i t y / a b n o r m a l -i t y on i t s c h a r a c t e r i s t i c s can be q u i c k l y d e t e r m i n e d . S e v e r a l a u t h o r s h a v e p u b l i s h e d p o p u l a t i o n and age norms f o r t h e 100--26-hue t e s t and these are summarized by Lakowski 1969 (b) (c) COLOR CON FUSION Color confusion t e s t s can be used to determine the extent to which an observer deviates from normal c o l o r v i s i o n . Lakowski I969 (a) d i f f e r e n t i a t e s between c o l o r d i s c r i m i n a t i o n and c o l o r confusion thus: Normal observers are capable o f d i s t i n g u i s h i n g a l a r g e number of c o l o r s whereas according t o some a u t h o r i t i e s the dichromat's c o l o r world i s l i m i t e d to l e s s than 30 d i s c r i m i n i b l e hues. These su b j e c t s confuse c o l o r s t h a t are e a s i l y recognizeable by the man i n the s t r e e t . I f someone mistakes one primary c o l o r f o r another we use the term c o l o r confusion to i n d i c a t e the gross nature of the mistake, but f o r those whose l o s s e s are l e s s extreme we t a l k about poor c o l o r d i s c r i m i n a t i o n , r e c o g n i z i n g t h a t there are wide v a r i a t i o n s i n t h i s a b i l i t y . 2 ? G e n e r a l l y , there are a set o f t e s t s which only dichotomize those who confuse c o l o r s from those who do not. These are c a l l e d Pseudoisochromatic p l a t e s (PIC p l a t e s ) and g e n e r a l l y c o n s i s t o f a figure-ground p a t t e r n i n a set o f c o l o r s which are confused by a c e r t a i n c l a s s i f i c a t i o n of c o l o r d e f e c t i v e observers. The I s h i l i a r a PIC p l a t e s , f o r example, use numbers, on a c i r c u l a r background. The e n t i r e p a t t e r n i s composed of c i r c l e s o f v a r i o u s s i z e s - the f i g u r e b eing com-posed o f one p a r t i c u l a r c o l o r e d o r group of coloured c i r c l e s that could be confused w i t h the background. Normal s u b j e c t s see the figure-ground r e l a t i o n s h i p whereas d e f e c t i v e s do not. One d i f f i c u l t y i n i n t e r p r e t i n g these t e s t s as pointed out by 29. Lakowski 1969 (a) pg 186. - 2 7 -Lakowski (1964) t h a t the f i g u r e can sometimes be d i s c e r n e d on the b a s i s o f b r i g h t n e s s cues and not j u s t c o l o r cues . These t e s t s are genera l ly cons idered u s e f u l o n l y f o r s c reen ing and t e s t i n g of gross d e f e c t s . A confus ion t e s t based on the 100 hue t e s t i d e a was developed by Farnsworth (1943) c a l l e d the Farnsworth Dichotbraous Test o r Pane l D-15 i s u s e f u l f o r gross measures l i k e the PIC p l a t e s . Aga in as i n the 100-hue t e s t the s c o r i n g p a t t e r n can be diagrammed and v i s u a l e s t imate o f d e f e c t s r e a d i l y made. I t can be seen t h a t the aforementioned t e s t s i n (a) and (b) can a l s o be used f o r i n v e s t i g a t i n g c o l o r c o n f u s i o n . I n g e n e r a l , because o f the r e l a t i v e l y shor t p e r i o d o f t ime r e q u i r e d t o t e s t each s u b j e c t , the 100 hue t e s t , the anoraolo-scope, and the PIC t e s t s are most o f t e n used . COLOR VISION AND AGEING A c c o r d i n g t o G i l b e r t (1957) and Lakowski (196U, the f i r s t major s t u d i e s o f the e f f e c t s o f age ing on c o l o r d i s c r i m -i n a t i o n were done i n the e a r l y 1940 ' s . T i f f i n and Kuhn (1942) i n v e s t i g a t e d the c o l o r d i s c r i m i n a t i o n o f f a c t o r y workers and noted p r o g r e s s i v e d e t e r i o r a t i o n a b i l i t y to d i s c r i m i n a t e c o l o r s between the ages o f 25 and 55 y e a r s . Smith (1943) however noted no s t r o n g t r e n d to d e t e r i o r a t i o n o f c o l o r d i s c r i m i n a t i o n w i t h age u n t i l over 65. As a response to T i f f i n and Kuhn ' s f i n d i n g s ( L a k o w s k i , 1964 p g . 57.) B o i c e , T i n k e r and Pa ter son (1948) found no s i g n i f i c a n t • d e t e r i o r a t i o n due to ageing be-tween 20 and 59 years - n e i t h e r d i d Chapanis (1950) . However, Chapanis r e p o r t e d s e v e r a l e a r l i e r s t u d i e s p o i n t i n g t o the - 2 8 -tendency of o l d e r subjects to have g r e a t e r d i f f i c u l t y w i t h blue-green, b l u e , and v i o l e t d i s c r i m i n a t i o n . These e a r l i e r authors s t a t e d t h a t the y e l l o w i n g o f the l e n s w i t h age may pl a y a r o l e i n the d i s c r i m i n a t i o n of the blue-end of the spectrum by a c t i n g l i k e a minus-blue absorption f i l t e r ( G i l b e r t , (1957))• Lakowski (1964) r e p o r t s t h a t O u e l l e t t e (1955) found age d i f f e r e n c e s i n c o l o r d i s c r i m i n a t i o n between two groups aged 20-30 and 75-85. However, O u e l l e t t e ' s d i f f e r e n c e s i n c o l o r d i s c r i m i n a t i o n extended to red , y e l l o w and green as w e l l as blue ( G i l b e r t , 1 9 5 7 ) . S t i l e s and Burch (1959) noted changes i n c o l o r matching w i t h age and along w i t h Warburton (1953) a t t r i b u t e d p a r t o f these changes w i t h changes i n the macular pigment d e n s i t y as w e l l as the l e n s t r a n s m i s s i o n c h a r a c t e r i s t i c s , Wright (1952) a l s o p o i n t s out th a t e l d e r l y observers may e x h i b i t some of the c h a r a c t e r i s t i c s o f t r i t a n o p i a on account o f y e l l o w i n g o f the eye media and 30 ••* the macular pigment,^. EXPERIMENTAL PRODUCTION OF DECREASES IN COLOR DISCRIMINATION CAUSED BY HYPOTHETICAL AGEING PROCESSES. Se v e r a l i n v e s t i g a t o r s have attempted to reproduce the c h a r a c t e r i s t i c decreases i n c o l o r d i s c r i m i n a t i o n observed i n va r i o u s ageing s t u d i e s . In ge n e r a l , the experimental v a r i a b l e s i n c l u d e attempts at e s t i m a t i n g the o c u l a r t r a n s -mission c h a r a c t e r i s t i c s and macular pigment d e n s i t y r e q u i r e d 30. Wright (1952) pg 510 -29-to produce c o l o r d i s c r i m i n a t i o n o f the o r d e r noted i n ageing o b s e r v e r s . Lakowski (1962b) i n v e s t i g a t e d the e f f e c t s o f i n c r e a s e s i n the s e l e c t i v e a b s o r p t i o n o f both l e n s and macular pigments on younger s u b j e c t s , and made comparisons to the data o f o l d e r s u b j e c t s . H i s des ign e n t a i l e d the p l a c e -ment o f minus-blue c o l o r f i l t e r s over the o b s e r v e r ' s eyes and t e s t i n g t h e i r matching ranges on the t h r e e anomaloscope equat ions (mentioned i n an e a r l i e r s e c t i o n ) . F i g u r e 4 i s the a b s o r p t i o n c h a r a c t e r i s t i c s o f the I l f o r d f i l t e r s as r e p o r t e d by Lakowski (1962) . A l though the f i l t e r s are supposed t o compensate f o r the d i f f e r e n c e between the 21 year o l d s u b j e c t s and the va lue s reported f o r o l d e r obser -v e r s , the curves i n d i c a t e t h a t the approximat ions are a l l o v e r - e s t i m a t e d by the I l f o r d s e r i e s f i l t e r s . Even so , Lakowski r e p o r t s t h a t o n l y the two most dense I l f o r d f i l t e r s (106 and 109) produced anomaloscope matching responses i n the 21 year o l d sub jec t s w h i c h were comparable to the best scores on the same measure of the l a s t two age groups (56-65 and 66-h ) . He f u r t h e r p o i n t s out t h a t i t r e q u i r e d a f i l t e r w i t h d e n s i t y c h a r a c t e r i s t i c s o f the o r d e r o f t w i c e the es t imated va lue s o f Sa id and W e a l e s ' s (1959) o l d e r s s u b j e c t ' s l e n s . T h i s r e s u l t was i n t e r p r e t e d as i n d i c a t i n g t h a t f u r t h e r a b s o r p t i o n s may be r e q u i r e d i n the e x p e r i m e n t a l l e n s e s o f young normal observer s i n o r d e r to account f o r the changes found i n aged s u b j e c t s . Because the a d d i t i on o f the macular pigment d e n s i t y (es t imated by Wald - 3 0 -Ilford filters 400 450 500 WAVELENGTH (nm) FiCjUFG 4 Experimental simulation f i l t e r s J used by Lakowski (1962) - 3 1 -f o r a 60 year observer to be 1 o p t i c a l d e n s i t y at 460 nm) would i n c r e a s e the curve c h a r a c t e r i s t i c s to be c l o s e r to the densest I l f o r d f i l t e r s , Lakowski concluded t h a t not j u s t the l e n s medium o r the macular pigment but at l e a s t both were needed to e x p l a i n c o l o r v i s i o n l o s s e s as a f u n c t i o n o f l o s s e s i n t r a n s m i s s i o n through the o o t i c a l media and macula : In the normal group we n o t i c e d t h a t age has e f f e c t s on the way people d i s c r i m i n a t e c o l o r s . There i s a g r a d -u a l l o s s o f f i n e d i s c r i m i n a t i o n and there a l s o seems to be an i n c r e a s e i n the i n c i d e n c e o f people whose performance i s l i k e t h a t o f major d e f e c t i v e s . The genera l p i c t u r e t h a t t h i s group p r e s e n t s i n terms o f the t y p i c a l changes as s u b j e c t s get o l d e r , c o u l d be e x p l a i n e d PARTLY by the r e p o r t e d i n c r e a s e s i n o p t i c a l l e n s d e n s i t i e s p l u s the i n c r e a s e i n macular p igment-a t i o n t h a t i s so o f ten p o s t u l a t e d . Some matching p a t t e r n s however, are too ' b i z a r r e ' t o be e x p l a i n e d i n terras o f such o c u l a r changes a l o n e . - 3 1 I t was a l s o p o i n t e d out i n t h i s same paper tha t l e n s changes c o u l d ' q u i t e s a f e l y ' account f o r d e t e r i o r 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 but t h a t g r e a t e r v a l u e s a t the v i o l e t end o f the spectrum would need t o be p o s t u l a t e d i n o r d e r t o account f o r the l e n s as b e i n g the ONLY f a c t o r i n v o l v e d i n the observed d e t e r i o r a t i o n due t o a g e . ^ 2 V e r r i e s t (1963 (a ) ) made use o f a group o f f i l t e r s r e sembl ing va lue s which i n c r e a s e i n t r a n s m i s s i o n from 3 1 . Lakowski (1962) pg 84. 3 2 . i b i d , pg 8 5 . - 3 2 -aoproximately 5 times the value o f the o c u l a r media as c a l c u l a t e d by Ludvigh and McCarthy (1938).-^ He a l s o used an extreme minus-blue f i l t e r which absorbed v i r t u a l l y a l l wavelengths below 500 nm. The f i l t e r c h a r a c t e r i s t i c s are shown i n Figure 5. Subjects were examined on a b a t t e r y of c o l o r v i s i o n t e s t s i n c l u d i n g AO H-R-R pseudo-isochromatic p l a t e s , 100 hue, panel D-15 and (Rayleigh match) p l u s Trendelenburg's T r i t a n match and v i o l e t - b l u e / g r e e n equations w i t h the Nagel Anomaloscope. U n f o r t u n a t e l y , V e r r i e s t d i d not attempt to account f o r l e a r n i n g e f f e c t s by counterbalancing the order o f pres-35 e n t a t i o n and the sequence o f f i l t e r s worn and t h e r e f o r e the r e s u l t s reported may not t r u l y represent the e f f e c t s of the e x p e r i m e n t a l f i l t e r s r e p o r ted. V e r r i e s t r e p o r t s matching r a t i o s f o r equations r e q u i r i n g short-wave-lengths are gen-e r a l l y weighted towards the blue f i l t e r of the p a i r . T h i s f i n d i n g i s understandable i n terms of the p h y s i c a l p r o p e r t i e s of the experimental f i l t e r s , i . e . , they absorb blue l i g h t . F u r t h e r , the matching ranges are enlarged, according t o V e r r i e s t , e s p e c i a l l y i n the Trendelberg match ( T r i t a n match) u s i n g the denser f i l t e r s , and f o r the K f i l t e r no match was p o s s i b l e . 33. As reported by Judd, P l a z a and Farnsworth (1950). 34. See s e c t i o n on the anomaloscope. 35. A s p i n a l l (1968) -33-V e r r i e s t (1963) Experimental f i l t e r s . J - 3 4 -M e a n p a r t i a l e r r o r s c o r e o o I X c o c n < H-(D U <+ n> <+ o c/> o o •1 a> o <-t-co a> o S3 o TJ 3 C 3 d 3 CP O c so m C D 3 L ! - • I -; i ! Ml) < u f { ? 5 S J - 3 5 -In a d d i t i o n , the experimental f i l t e r s produced d e t r i -mental e f f e c t s i n c o l o r d i s c r i m i n a t i o n , as measured by the 100 hue t e s t , mainly i n ' t h e regions of the blue-green and 3 6 red hues. A t r i t a n o p i c c h a r a c t e r i s t i c was only observed when the extreme minus-blue f i l t e r nK" was used w i t h the Panel D-15 t e s t o r AO H-R-R P l a t e s , or under.severely reduced i l l u m i n a t i o n . In a r e l a t e d study, V e r r i e s t et a l . (1963 b) repo r t t h a t normal subjects become wh o l l y t r i t a n -o pic at 0 .216 Lx. The r e s u l t s of reduced i l l u m i n a t i o n upon 100 hue scores f o r 2 5 normal su b j e c t s aged 20-24 under i l l u r a i n a n t TC T are presented i n Figure 6. E f f e c t s of p u p i l s i z e should be taken i n t o c o n s i d e r a t i o n according to Weale 37 (1961) who p o s t u l a t e s t h a t absorption c h a r a c t e r i s t i c s o f le n s i n c r e a s e s at the centre of the le n s due to i n c r e a s e s i n the o p t i c a l path l e n g t h (Bouger's Law)., V e r r i e s t s t r e s s e s t h i s f a c t o r as one of p o s s i b l e importance i n accounting f o r the ageing p o p u l a t i o n parameters of c o l o r v i s i o n . Asoinall (I96&) i n v e s t i g a t e d the e f f e c t s of simulated macular changes on the 100 hue t e s t . As w i t h V e r r i e s t , one of the experimental f i l t e r s used by the author was extreme. Figure 7 shows the s p e c t r a l d e n s i t i e s o f the macular s i m u l -36. V e r r i e s t p o i n t s out tha t of the two r e g i o n s , the b l u e / green region i s e f f e c t e d more than the red (1963) p g . l 8 £ 37. i b i d . (1963) -36-a t i o n f i l t e r s used by A s p i n a l l i n the above mentioned study. He d i d not note the xanthophyll s o l v e n t . " ' His i l l u m i n a t i o n l e v e l s were c a l c u l a t e d to be i n accordance w i t h the reported l e v e l s of V e r r i e s t * s C a n d E f i l t e r s and i n u s i n g three d e n s i t i e s of x a n t h o p h y l l had s i x experimented c o n d i t i o n s p l u s a b a s e l i n e measure on a l l s u b j e c t s . With the experimental f i l t e r s on young normal eyes A s p i n a l l found a s h i f t i n the expected e r r o r a x i s , due to ageing of observers, about f i v e or so caps c l o c k w i s e . V e r r i e s t ' s data on t h i s p o i n t suggest a s h i f t i n the same d i r e c t i o n although not as l a r g e at the red end as reported by A s p i n a l l . A small e r r o r 'bulge' increased w i t h i n c r e a s i n g f i l t e r den-s i t y at cap 25 as w e l l . Test experience i s purported to p l a y a r o l e i n the r e s u l t s and A s o i n a l l analyzed the d i f f e r e n c e s between experienced and inexperienced s u b j e c t s . He found t h a t experienced subjects performed g e n e r a l l y b e t t e r i n a l l c o n d i t i o n s than d i d inexperienced s u b j e c t s and, t h a t as a l l apparent l u m i n o s i t i e s are the same, the d i f f e r e n t i a l e f f e c t of the experimental f i l t e r s must be due to d i f f e r e n c e s i n the s o e c t r a l c h a r a c t e r i s t i c s of the f i l t e r s . F u r t h e r a n a l y s i s of the data l e d the author t o report s i g n i f i c a n t d i f f e r e n c e s f o r both l u m i n o s i t y and f i l t e r a bsorption changes but t h a t " i n c r e a s e d f i l t e r d e n s i t y i s more d e t r i m e n t a l to 100 hue performance than reductions i n l u m i n o s i t y " . The 38. As has been noted e a r l i e r , the peak absorption may vary as a f u n c t i o n of the solvent but, i t appears from the data presented by the author t h a t chloroform was used. -37-WAVELENGTH (nm) FlQUre 7 A s p i n a l l ' s (1968) Experimental ^ simulated Macular Pigment f i l t e r s (Xanthophyll i n Chloroform) • -38-conclusion stated here i s understandable in view of the extreme concentrations used in the experimental f i l t e r s * SUMMARY AftD PROPOSAL I t can be seen from the preceding review that (a) there i s evidence f o r the existence of both macular and l e n t i c u l a r pigmentation in the human eye and (b) that these pigments a f f e c t performance on color v i s i o n t e s t s * Further, i t can be postulated from a reasonably large amount of comparative and experimental evidence that one or both of the pigments increase in vivo with age and, along with reductions in r e t i n a l illumination (either as a r e s u l t of these increases or due to p u p i l l a r y changes etc.) contribute to the observed deterioration of color v i s i o n with ageing. Experimental approximations of these two pigments have not been as accurate as possible i n view of the psychophysical and p h y s i o l o g i c a l evidence accumulated f o r t h e i r existence and, as these approximations a f f e c t the in t e r p r e t a t i o n of r e s u l t s in terms of there g e n e r a l i z a b i l i t y to human ageing processes, a higher degree of accuracy might be desi r a b l e . - 3 9 -> CO LU Q < O O |.0 o.S 0.1 CA O.I Wald's macular pigment and I l f o r d f i l t e r s Lakowski ( 1962 ) 400 45o J5ao 550 U lo O.io Wald's 'macular pigment' estim -o f Said Weale's l e n s stimates f o r k 40o ^5Q -5bO WAVELENGTH (nm) Figure 8 uo EXPERIMENT I . The present experiment was based upon the Lakowski (1962) , V e r r i e s t (1963) and A s p i n a l l (1968) s t u d i e s a l though numerous m o d i f i c a t i o n s were i n s t i t u t e d i n l i n e w i t h the exper imenta l aims presented above. The author attempted to s imula te the l e n s and macular a b s o r p t i o n c h a r a c t e r i s t i c s s e p a r a t e l y , based upon the r e n o r t s o f v a r i o u s au thor s covered e a r l i e r , and study t h e i r e f f e c t s upon performance o f s e v e r a l c o l o r v i s i o n t e s t s . APPARATUS The Lens S i m u l a t i o n F i l t e r s The l e n s approximat ion f i l t e r s were based upon the c h a r a c t e r i s t i c age-dependant curves as r epor ted by Sa id and Weale (1959) . Compensation f i l t e r s were cons t ruc ted u s i n g the 21 y e a r - o l d ' s c h a r a c t e r i s t i c s as a b a s e l i n e . Quartz 39 c e l l s , des igned to f i t a s p e c t a c l e - l i k e l e n s h o l d e r were f i l l e d w i t h a c o l o r e d l i q u i d des igned to approximate the l e n s p i g m e n t a t i o n . The method o f d e r i v i n g the d e n s i t i e s o f t h i s s o l u t i o n i s as f o l l o w s : F i r s t l y , two stock s o l u t i o n s o f extreme d e n s i t y (1 .50 O p t i c a l D e n s i t i e s a t 403 nm) were made up from two commerc ia l ly a v a i l a b l e w a t e r - s o l u b l e dyes : P o l a r Y e l l o w 2G conc.Q Neolan Grey RC 200$ ^ 39 . Pa th l e n g t h o f l i q u i d 5.0mm LO, My thanks to D r . R . S . S i n c l a i r , Department o f Chemis t ry , P a i s l e y C o l l e g e o f Technology, P a i s l e y , S c o t l a n d , f o r sugges t ing these dyes . 41 both o b t a i n a b l e from CIBA-Geigy L t d . The P o l a r Y e l l o w was used to achieve the increase i n blue-absorption w h i l e the Neolan Grey was used to.reduce t r a n s m i s s i o n across the spectrum. Because of the r e l a t i v e l y small amounts of s o l u t i o n r e q u i r e d and the extreme co n c e n t r a t i o n of the dyes the p r e c i s e measurement of the conc e n t r a t i o n s BY WEIGHT was i m p r a c t i c a l . Therefore c o n c e n t r a t i o n s were approximated by d i l u t i o n w i t h the solvent ( i n t h i s case w a t e r ) . The absorp-t i o n c h a r a c t e r i s t i c s were measured on a UNICAM SP 800 r e c o r d -i n g s p ectrophotometer.^ As the r e a l t o t a l o p t i c a l d e n s i t y measurements should i n c l u d e the f a c t o r s of the c e l l , s o lvent and dye, the second beam of the spectrophotometer was used 42 w i t h no blank i n p l a c e . Thus, measurements o f the e x p e r i -mental c e l l s gave estimates of the t o t a l o p t i c a l d e n s i t y of the f i l t e r as a whole. Some co n c e n t r a t i o n s proved to be cloudy due to inhomogeneties i n the dye. F i l t e r i n g would not remove t h i s and so the s o l u t i o n s were c e n t r i f u g e d f o r 5-7 minutes at 9.000 g f s to remove the suspension. The f o u r c o n c e n t r a t i o n s o f Approximating F i l t e r s designed t o compen-sate f o r the estimated amounts o f l e n s pigment already 41. This use of t h i s instrument was provided courtesy o f the M i c r o b i o l o g y Department, U n i v e r s i t y o f B r i t i s h Columbia. 42. G e n e r a l l y , when measuring absorbance o f chemicals i n s o l u t i o n , the c h a r a c t e r i s t i c s of the c e l l and the solv e n t used are balanced out i n a second l i g h t path i n the instrument and n u l l i f i e d i n the r e c o r d i n g . 4 2 . extant i n the 2 1 - y e a r - o l d eye are shown i n f i g u r e 1 . 9 . The Macular 'Pigment' Simulation F i l t e r s Compensation f i l t e r s f o r the s o - c a l l e d macular pigment were constructed on the b a s i s of the estimated values of Bone and Sparrock ( 1 9 7 1 ) . Although i t can r e a d i l y be seen tha t estimates f o r the macular pigment are q u i t e v a r i a b l e , i f i t f i r s t l y can be assumed t h a t there i s a macular p i g -ment, there seems t o be evidence f o r an average d e n s i t y o f about 0 . 5 - 0 . 6 O.D. Bone and Sparrock's e s t i m a t i o n of the 'average' o p t i c a l d e n s i t y i s 0 . 5 2 9 O.D. T h i s value was decided upon i n view o f i t s consistency w i t h other estima-t i o n s and the r e l a t i v e l y l a r g e sample. Four d e n s i t i e s were made based on the assumption that the sub j e c t s i n t h i s i n -v e s t i g a t i o n had the mean amount of pigment.^ These f i l t e r s would, then add t o the e x i s t i n g amount of pigment (at 455nm) by 0 . 2 , 0 . 4 , 0 . 6 , and 0 . 8 O.D. This would make the maximum macular pigment (experimental p l u s mean) f o r a h y p o t h e t i c a l eye c l o s e to 1 . 3 3 O.D. L u t e i n Xanthophyll ( C ^ Q H ^ O H ^ ) was d i s s o l v e d i n Chloroform t o y i e l d the c h a r a c t e r i s t i c two-peaked curve at f o u r c o n c e n t r a t i o n s . Due t o the nature of 4 3 . This assumption was made f o r both the l e n s and macular pigment. Although i t i s to be recognized t h a t the l e n s s i m u l a t i o n f i l t e r s are f o r 2 1 year o l d eyes, the curves i n f i g u r e 1 p o i n t to the r e l a t i v e l y small d i f f e r e n c e i n the f i r s t 1 0 years. 4 3 . 4oo Soo WAVELENGTH (nm) Figure 9 Absorption C h a r a c t e r i s t i c s of the Simulated Lens F i l t e r s (Approximations of Ages as reported by Said and Weale (1959) ) . UK. the crude Xanthophyll used i t was impossible to ob t a i n c o n s i s t e n t r e s u l t s by weight and t h e r e f o r e , as w i t h the l e n s approximations, the concentrations were determined by o p t i c a l d e n s i t y . A stock s o l u t i o n of 1 gram x a n t h o p h y l l i n 100 ml. chloroform was made and f i l t e r e d 3 times to remove i m p u r i t i e s . D i l u t i o n of the stock s o l u t i o n to the req u i r e d d e n s i t i e s was achieved w i t h the use o f the spectro-photometer mentioned p r e v i o u s l y . The s p e c t r a l absorption c h a r a c t e r i s t i c s f o r the 4 macular f i l t e r s are shown i n f i g u r e 10. Quartz c e l l s o f s i m i l a r nature to the l e n s -s i m u l a t i o n f i l t e r s were used t o house the l i q u i d (path l e n g t h 2.5mm).^ Due t o t h e e xtremely v o l a t i l e nature o f the solvent, the s o l u t i o n s were kept i n glass-stoppered f l a s k s . As a pr e c a u t i o n a g a i n s t the p o s s i b i l i t y o f both ' l e n s ' and 'macular* f i l t e r s o l u t i o n s being subjected to li g h t - p r o d u c e d degradation, samples o f a l l c o n c e n t r a t i o n s were l e f t i n a f l u o r e s c e n t - s o u r c e i l l u m i n a t e d room f o r one week and then subjected to spectrophotometric a n a l y s i s . No observable changes were found i n any of the r e s u l t a n t LL. A l l spectrophotometric measurements were made w i t h the experimental quartz c e l l s c o n t a i n i n g t h e i r r e s p e c t i v e l i q u i d s . The 2.5mm c e l l s were used f o r the macular pigment s i m u l a t i o n (due t o t h e i r narrow opening) i n an attempt to prevent excessive evaporation d u r i n g t e s t i n g . Stoppers o f neoprene rubber and s e v e r a l other substances were found to p a r t i a l l y d i s s o l v e i n the chloroform, and t h e r e f o r e no stoppers were used. The c e l l l e v e l s were maintained as f u l l as p o s s i b l e d u r i n g the experiment by f i l l i n g w i t h a p i o e t t e . 4 5 . curves. In the experimental s i t u a t i o n s mentioned i n the f o l l o w i n g p a r t of t h i s paper, the s o l u t i o n s were subjected to t u n g s t e n - l i g h t o n l y , and then only when the observers were e n t e r i n g or l e a v i n g the room. A f t e r the experiments were concluded, the s o l u t i o n s were again measured and no changes were found. Figure 11 (a-d) g i v e s the s p e c t r a l absorption c h a r a c t e r i s t i c s of the 16 combinations of l e n s and macular pigment s i m u l a t i n g f i l t e r s which w i l l be used (as w e l l as the f i l t e r s shown i n f i g u r e 9 and 10) i n the experimental s i t u a t i o n s described h e r e i n . Table 3 g i v e s the b r i g h t n e s s values {%) o f the l e a s t and most dense s i m u l a t i o n f i l t e r s and of the most dense combinations. U6 F i G l i r G 1Q Absorption C h a r a c t e r i s t i c s of J the Simulated macular pigment f i l t e r s . 47. WAVELENGTH (nm) FlQUre 113 Absorption C h a r a c t e r i s t i c s of Macular Si m u l a t i o n F i l t e r 'A* and Experimental lens values 4 8 . WAVELENGTH (nm) FinUTQ 11b Absorption Characteri 1 of macular Simulation f i l t e r !B' and experi mental lens values. P i n n r o 11 r Absorption C h a r a c t e r i s t i c s of r i L J U l L I IO j ^ ^ a j . s i m u l a t i o n f i l t e r »C» and experimental l e n s v a l u e . 51. Table I I I Brig h t n e s s Values of the Least and Most Dense Experimental Simulation F i l t e r s . (LENS) EXT 85 31 94 (Macular pigment) D 88 A 93 EXT + D 74.8 Table IV Simu l a t i o n Conditions f o r Experiment I Macular Simulation (Space) A B C D OLens i Len S i m u l a t i o n Macular 31 314A 31+B 31+C 3 M D 31 45 45+A 45+B 45+C 45+D C 45 63 63+A 63 +B 63+C 63 B 63 EXT EXT+AEXT+B EXT+C EXT+D A EXT 52 METHOD Twelve observer s between 22 and 25 (mean age 23.0) were s e l e c t e d from a group who v o l u n t e e r e d t o be s u b j e c t s f o r t h i s s tudy and were randomly as s igned t o one o f f o u r e x p e r i m e n t a l groups . T e s t i n g took p l ace at the U n i v e r s i t y o f B r i t i s h Columbia , Psychology Department between J u l y 5th and August 4 t h , 1972. A l l sub jec t s were screened f o r gross c o l o r v i s i o n d e f e c t s w i t h the I s h i h a r a and American O p t i c a l H-H-R Pseudoi sochromat ic p l a t e s ^ and f o r near a c u i t y w i t h the C.W. DIXEY ACUITY CARD. Only I s h i h a r a o r AO H-R-R scores o f zero were t r e a t e d as acceptab le f o r observer s as were a c u i t y scores i n d i c a t i v e o f N5 v i s i o n . Upon i n i t i a l s c reen-i n g o f s u b j e c t s , two observer s f a i l e d t o meet these c r i t e r i a and were r e p l a c e d . A l l t e s t ing '^ premeasures and e x p e r i m e n t a l measures were done w i t h the r i g h t eye o n l y . I f the sub jec t wore c o r r e c t i v e l e n s e s f o r the near a c u i t y t e s t , these l ense s were worn throughout the exper iment . A f t e r a p p r o x i -mately ten minutes i n reduced i l l u m i n a t i o n , each observer was t e s t e d on the t h r e e equat ions o f the P i c k f o r d - N i c h o l s o n anomaloscope and the Farnswor th-Munse l l 100-hue t e s t to determine b a s e l i n e measures. As a p r e c a u t i o n a g a i n s t p o s s i b l e d e t r i m e n t a l e f f e c t s produced by the l ense s a lone on performance, f o u r s u b j e c t s , one from each group, were 45 . I l l u m i n a t i o n o f 100 e q u i v a l e n t l u x . 5 3 . t e s t e d under two a d d i t i o n a l c o n d i t i o n s : 1, 5.0mm auartz c e l l ( w a t e r - f i l l e d ) 2. 2.5mm quartz c e l l ( c h l o r o f o r m - f i l l e d ) Both of these groups showed no s i g n i f i c a n t or systematic d e v i a t i o n s from t h e i r b a s e l i n e r a t e s . As these i n i t i a l t e s t i n g c o n d i t i o n s were counterbalanced among the f o u r sub-j e c t s , l e a r n i n g e f f e c t s were n e g l i g i b l e . A l l subjects were f i t t e d w i t h a spe c t a c l e device i n which the l e f t eye was occluded and the r i g h t eye side adapted to hold two quartz c e l l s . A l l s u b j e c t s were then t e s t e d under the s i x condi-t i o n s summarized i n Table IV. For the purpose o f a n a l y s i s , the c o n d i t i o n s where t h e r e i s only one SIMULATIONS FILTER being used, are conceptualized as u s i n g zero amounts o f the other f i l t e r d e n s i t y . In the experimental s i t u a t i o n , s u b j e c t s always had two c e l l s i n f r o n t of t h e i r r i g h t eye and were not informed of the d e n s i t i e s i n each c e l l . Under each of the s i x c o n d i t i o n s , 8 t e s t s were made: Box 1 100-hue t e s t Box 2 100-hue t e s t Box 3 100-hue t e s t Box h 100-hue t e s t Red-Green Equation Anomaloscope Yellow-Blue Equation Anomaloscope - Blue-Green Equation Anomaloscope Pseudoisochromatic P l a t e s (Dvorine and I s h i h a r a ) 5U. The order o f p r e s e n t a t i o n o f these t e s t s and the macular pigment s i m u l a t i o n f i l t e r s were counterbalanced so t h a t no two s u b j e c t s under any of the s i x c o n d i t i o n s received the f i l t e r s or the sequence of t e s t s under each of them i n the same order. F o r t y - e i g h t measures ( s i x c o n d i t i o n s x e i g h t measures) were taken on each of the twelve observers d u r i n g the experimental s e s s i o n . The 100-hue and the Pseudoisochromatic p l a t e s were done under an approximation of I l l u m i n a n t 'C at 100 e q u i v a l e n t l u x , w h i l e the three anomaloscope equations were set i n accord-ance w i t h Lakowski's (1971) measurements of model I which are summarized below: R-G Equation 1.9 n i t s (candelas per square metre) T-B Equation 3.0 n i t s B-G Equation 2.2 n i t s The r e t i n a l i l l u m i n a t i o n f o r the anomaloscope at these l e v e l s i s between 30 and 50 Trolands (1 degree subtense). As the anomaloscope s e t t i n g s had t o be changed many times d u r i n g an experimental s e s s i o n , the b r i g h t n e s s of the matching f i e l d was determined each time w i t h the use of an S.E.I. Exposure Photometer. RESULTS The data c o l l e c t e d from the e i g h t response c a t e g o r i e s i n t h i s experiment can be seen as measures on three d i s c r e e t 5 5 . t e s t s : the Anomaloscope, the Farnsworth-Munsell 100-hue t e s t and the Pseudoisochromatic P l a t e s . Each o f the three c a t e g o r i e s w i l l be d e a l t w i t h s e p e r a t e l y , and as a consequence the assumption must be made that there are no s i g n i f i c a n t i n t e r a c t i o n s between them. Because of the small number o f sub j e c t s per group, d e s c r i p t i v e s t a t i s t i c s were employed, i n s t e a d o f i n f e r e n t i a l t ypes. Group means and standard d e v i a t i o n s f o r r e s u l t s have been presented i n e i t h e r t a b u l a r o r graphic form. 56. The Anomaloscope The C o n t r o l Condition Table IV g i v e s the raid-points and standard d e v i a t i o n s f o r the three equations of the Anomaloscope f o r the NORMAL-46 NO LENS and C o n t r o l groups* The red-green equation c l e a r l y shows the l e a s t v a r i a n c e of the t h r e e , w h i l e the other two vary s l i g h t l y more. The means o f each equations M i d - P o i n t s w i l l be used as the Standard Mid-Points f o r comparison. The Means and Standard D e v i a t i o n s f o r s i n g l e f i l t e r c o n d i t i o n s are presented i n Table V . The l a t t e r two equations, and e s p e c i a l l y the y e l l o w - b l u e , are s t r o n g l y a f f e c t e d by the denser values of both l e n s and macular pigment s i m u l a t i o n f i l t e r s . The Mid-Points and Ranges (2x standard d e v i a t i o n s ) a r e , r e s p e c t i v e l y , more e r r a t i c and enlarged than the c o n t r o l s . These do not apoear to be d i r e c t e d s h i f t s towards one anomaloscope f i l t e r or the o t h e r , and, contrary to what would be expected from the p h y s i c a l p r o p e r t i e s of the s i m u l a t i o n f i l t e r s , l a r g e r p ro-p o r t i o n s of blue do not seem to be i n d i c a t e d . 4£. The Mean and Standard D e v i a t i o n are c a l c u l a t e d on the lowest and highest acceptable scores f o r each subject Therefore; the Mean can be seen as the midpoint and the Standard D e v i a t i o n can be seen as one-half o f the Range. 57. Table V Anomaloscope Mid-Points and Standard D e v i a t i o n s f o r the C o n t r o l C o n d i t i o n s . GROUP Zero d e n s i t y I I I I I I IV c e l l s c o n t r o l Red-Green Equation X 40.5 42 .1 41.6; 38.8 40.5 SD 0 .9 1.9 1.2 1.6 0 .4 Yellow-Blue Equation X 38 .4 43.5 40.8 41.5 41 .1 SD 1.9 3.0 1.5 3.4 3.5 Blue-Green Equation X 43.0 40.5 42 . 5 kh.8 4 2 . 1 SD 3.3 1.7 2 .1 2 .9 0 .5 T o t a l s ( f o r comparison purposes) Mean Mid-Point Red-green 40 .6 Yellow-blue 41 .1 Blue-Green 41.7 58 Table VI Anomaloscope Mid-Points and Standard D e v i a t i o n s f o r Si n g l e F i l t e r C o n d i t i o n s . A B C D 31 45 63 EXT Red-Green Equation X 39.5 41 .1 40.3 40.3 40.5 41 .1 41 .1 39.8 SD 1.2 2 .4 2 . 3 1.8 0 .9 2 . 9 2.7 1.8 Yellow-Blue Equation X 43.5 42 . 0 47 .0 34.8 37 .1 44 .0 41.5 40 .6 SD 4 .4 3.8 10.4 14 .7 6.8 13.0 9 .7 15 .2 Blue-Green Equation X 43 .0 43.0 43 .0 38.0 40.5 39.5 45 .0 4^.0 SD 5 .4 5 .4 11.4 14.5 6.1 9 . 0 6.4 5 .4 59 Table V I I Anomaloscope Mid-Points .and Standard D e v i a t i o n s f o r T w o - f i l t e r C onditions. (a) Red-Green Equation Lens Simulation Macular Simu l a t i o n 31 45 63 EXT. A X 40 .1 42 . 4 41 .4 39.3 SD 1.8 2 .0 1.1 0 .7 B X 40.2 41.3 41.0 40.0 SD 1.3 2.3 0 .8 1.9 C X 40.7 41.3 41 .7 39.7 SD 1.4 2 .1 1 .3 1.5 D X 40 .7 41 .0 41.2 39.8 SD 1.5 2 .5 1.6 1.1 60. (b) Yellow-Blue Equation Macular Simulation Lens Simulation 31 45 63 EXT A X 38.8 52 .0 39.7 38.8 SD 10.2 15.1 12 .6 20 .4 B X 39.2 45 .7 41 .0 31.3 SD 11.9 9.2 8.2 23 .4 C X 36.8 44.8 32 .3 40 .7 SD 17 .6 11.8 24.2 6.7 D X 38.3 3 0 . 7 35.2 31.2 SD 19 .6 23 .1 26.2 26 .9 61. (c) Blue-Green Equation Lens Simulation EXT 43.5 4 .9 40.2 12 .1 Macular Simulation C X 44 .7 45 .7 35.2 45.8 11.5 43.8 31 45 63 A X 43.7 36.5 46.2 SD 9 .7 8.9 8.3 B 1 46.8 47.0 44.3 SD 8.9 10 .6 15 .0 C X 44.7 45 .7 35.2 SD 12.7 12.2 25 .6 D X 37.2 41.8 45.0 SD 24 . 0 16 .0 19.0 6 ? . Table VI presents the mean raid-points and matching ranges f o r the T w o - F i l t e r Conditions« The red-green equa-t i o n remains unaf f e c t e d -by the experimental procedure. Every c o n d i t i o n remains close to the c o n t r o l mid-point w i t h low matching ranges. The yellow-blue equation shows more e r r a t i c mid-points and increased matching ranges w i t h i n c r e a s i n g f i l t e r d e n s i t y . The most dense f o u r combinations show mid-point s h i f t s toward the y e l l o w side of the equation w i t h the matching ranges encompassing up t o 54 Anomaloscope u n i t s : almost t h r e e - q u a r t e r s of the t o t a l p o s s i b l e range of the instrument. The blue-green equation shows mid-point s h i f t s toward the blue f i l t e r and matching ranges do not show as l a r g e i n c r e a s e s as d i d the yellow-blue equation. The Farnsworth-Munsell 100-Hue Test The means and standard d e v i a t i o n s of each o f the f o u r boxes are presented, f o r the s i n g l e c e l l c o n d i t i o n i n Table V I I I ( a ) . I t appears from these data that increases i n macular s i m u l a t i o n d e n s i t y tends to a f f e c t Box three scores s t r o n g l y ; Box one and f o u r scores s l i g h t l y and Box two scores h a r d l y at a l l . The l e n s s i m u l a t i o n f i l t e r s tend to a f f e c t Box three scores s t r o n g l y , Box one and f o u r scores s l i g h t l y , and Box two scores h a r d l y a t a l l but note, as a Function of 63. Decreasing F i l t e r Density and not i n c r e a s i n g d e n s i t y as i n the macular s i m u l a t i o n . This f i n d i n g can be a t t r i b u t e d to subject b i a s as the 31 a n d D groups were the same sub j e c t s (see Table I V ) . The t w o - c e l l c o n d i t i o n means and standard d e v i a t i o n are presented i n Table V I I I ( b ) . Again, Box three seems t o be a f f e c t e d most by i n c r e a s e s i n f i l t e r d e n s i t y . A l l e x p e r i -mental groups show a general tendency t o higher scores w i t h i n c r e a s e s i n f i l t e r d e n s i t y w i t h the' D-lens s i m u l a t i o n c o n d i -t i o n s a f f e c t i n g c o l o r d i s c r i m i n a t i o n most. Pseudoisochromatic P l a t e s The scores of the oseudoisochromatic p l a t e s showed no mistakes f o r any o f the s u b j e c t s under any f i l t e r c o n d i t i o n i n Experiment I . 64. Table V I I I Means and Standard D e v i a t i o n s f o r 100 hue t e s t (By Box) (a) S i n g l e C e l l C o nditions 100 Lux Box 1 Box 2 Box 3 Box 4 A (only) X 5.0 5.7 7.0 4.0 SD 4.5 4.0 4.2 3.3 B (only) X 5.3 4.0 6.7 5.3 SD 1.9 5.7 3.8 1.9 C (only) X 8.0 4.0 8.0 5.0 .SD 8.6 3.3 8.6 7.1 D (only) X 11.0 5.3 13.3 10.7 SD 5.1 3.7 5.0 6.8 31 (only) X 7.7 8.0 13.7 10.3 SD 8.2 0. 8.2 4.9 45 (only) X 10.0 3.0 11.3 4.0 SD 4.3 1.4 2.5 3.3 63 (only) X 4.0 6.7 2.7 2.7 SD 5.7 5.0 1.9 1.9 EXT(only) X 5.3 4.0 5.3 2.7 SD 1.9 3.3 1.9 1.9 6 5 . (b) Box 1 A - 3 1 X 5 . 3 SD 5 . 0 A - 4 5 X 4 . 0 SD 5 . 7 A - 6 3 X 1 3 . 3 SD 5 . 0 A-EXT X 5 . 7 SD 4 . 0 B - 3 1 X 4 . 0 SD 5 . 7 B - 4 5 X 6 . 7 SD 9 . 4 B - 6 3 X 1 0 . 7 SD 1 . 9 B-EXT X 4 . 7 SD 5 . 9 Box 2 Box 3 Box 4 8 . 0 1 2 . 7 7 . 3 1 1 . 3 9 . 6 7 . 7 6 . 3 8 . 3 5 . 3 4 . 7 9 . 1 1 . 9 4 . 3 1 3 . 3 1 2 . 7 3 . 3 6 . 8 6 . 3 5 . 0 1 3 . 0 1 2 . 0 1 . 4 3 . 7 6 . 7 1 0 . 7 1 8 . 7 2 . 7 1 0 . 0 1 3 . 6 1 . 9 6 . 3 1 5 . 7 5 . 3 5 . 8 1 7 . 4 5 . 0 1 6 . 0 1 5 . 0 6 . 3 7 . 3 9 . 2 4 . 0 5 . 3 9 . 7 1 1 . 0 3 . 8 8 . 0 1 0 . 6 66. Box 1 Box 2 Box 3 Box 4 C-31 X 4.0 5 . 7 15.0 9.7 SD 3.3 5.4 6.1 11.0 C-45 X 6 .7 12.3 25.3 9.0 SD 5.0 10.2 30.3 7.8 C-63 X 1 0 . 7 7.0 6.3 9.0 SD 5.0 5.4 6.3 6 . 7 C-EXT X 7.7 4.3 14.3 9 . 7 SD 2.9 0.5 6.3 1 . 7 D-31 X 6 .7 14.0 2 4 . 7 14.3 SD 3.8 7.3 4.1 9.0 D-45 X 1 4 . 7 12.3 19.3 16.3 SD 11.5 11.1 8.1 6.0 D-63 X 12.0 14.3 17.0 11 . 7 SD 5.7 4.5 4.2 7 . 6 D-EXT X 8.3 7.3 2 0 . 7 15 . 7 SD 5.9 5.2 12.2 8.3 67. E X P E R I M E N T I I To i n v e s t i g a t e the a d d i t i o n a l e f f e c t s o f changes i n i l l u m i n a t i o n o f luminance on c o l o r v i s i o n t e s t s c o r e s , a study was conducted based upon an adap ta t ion o f the f i n d i n g o f s e v e r a l a u t h o r s . The s i m u l a t i o n f i l t e r s r epor ted i n Experiment I were used i n concer t w i t h r e d u c t i o n s i n i l l u m i n a t i o n t o determine whether s imula ted macular and l e n t i c u l a r a b s o r p t i o n n l u s r e d u c t i o n s i n the amount o f l i g h t r each ing the eye would e f f e c t c o l o r v i s i o n t e s t scores from young sub jec t s i n a sys temat ic manner. V e r r i e s t ' s (1963) age norms f o r the 100-hue t e s t show g r a d u a l i n c r e a s e s i n the b lUe-green ; and red reg ions o f the t e s t w i t h i n c r e a s e s i n age and w i t h r e d u c t i o n s i n i l l u m i n a t i o n . He concluded from t h e s e , as w e l l as o t h e r f i n d i n g s , t h a t i n case o f a c q u i r e d b l u e - y e l l o w d i s c r i m i n a t i o n d e f i c i e n c y : . . . t h e r e t i n a would become l e s s s e n s i t i v e to l i g h t so t h a t i t s sensory c o n d i t i o n s would s h i f t . . . . the b l u e - y e l l o w d i s c r i m -i n a t i o n de fec t observed would be due t o a " m e s o p i s a t i o n " o f the v i s i o n . I f t h i s e x p l a n a t i o n were t r u e , the d i s c r i m i n a t i o n would improve i f the i l l u m i n a n c e were i n c r e a s e d and would become wQrse i f the i l l u m i n a n c e were d e c r e a s e d . ' As can be seen from the r e s u l t s o f Experiment I , s imula ted changes o f both l e n s and macular a b s o r p t i o n do 47 . V e r r i e s t (1963) Pg 194-195 6 8 . not adequately account f o r the ageing changes observed by V e r r i e s t on the 100-hue p r o f i l e s but together w i t h r e d u c t i o n s i n i l l u m i n a t i o n o f the hue d i s c r i m i n a t i o n t e s t s and screening p l a t e s , these changes may be more d r a s t i c . The anomaloscope matching data f o r the yellow-blue and b l u e -green equations shows some d e v i a t i o n from n o r m a l i t y along the l i n e s of an ageing p o p u l a t i o n as reported by Lakowski ( 1 9 6 2 ) . Looking at these r e s u l t s i n view o f V e r r i e s t ' s c o n c l u s i o n s , the questions of INCREASES i n the luminance of the anomaloscope might produce r e d u c t i o n s i n the v a r i a -b i l i t y o f the ranges and raid-points found i n Experiment I . M o d i f i c a t i o n s t o the P i c k f o r d - N i c h o l s o n Anomaloscope (Model I I I ) In order to achieve the b r i g h t n e s s l e v e l s r e q u i r e d f o r the i n v e s t i g a t i o n s of experiment I I , m o d i f i c a t i o n s were made to the Pickford-NichoLson Anomaloscope used throughout t h i s experiment. These m o d i f i c a t i o n s were made i n the 1 g summer and e a r l y f a l l o f 1 9 7 1 by the author. The P i c k f o r d - N i c h o l s o n Anomaloscope has been described by Lakowski ( 1 9 7 1 ) as a simple c o l o r i m e t e r . I t i s b a s i c a l l y an a d d i t i v e c o l o r i m e t e r which contains a source of i l l u r a -2*3. My thanks to K e i t h Waldron, t e c h n i c i a n , Psychology Department, U.B.C. f o r h i s help i n the m o d i f i c a t i o n s of t h i s instrument. 69. i n a n t ' A 1 l i g h t , two se t s o f f i l t e r h o l d e r s and s h u t t e r s and two i n t e g r a t i n g chambers, each opening to a s i n g l e h a l f . o f the same b i p a r t i t e f i e l d . Three se t s o f f i l t e r s are i n the P i c k f o r d - N i c h o l s o n Anomaloscope and w i t h them, t h e o r e t -i c a l l y , a l l c l a s s i c a l forms o f c o l o r v i s i o n de fec t can be t e s t e d ( L a k o w s k i , 1971) : Equa t ion Standard Defect Red - Green - Y e l l o w Protan - Deutan Y e l l o w - B lue - N e u t r a l T e t a r t a n B lue - Green - B lue-Green T r i t a n The m o d i f i c a t i o n s r epor ted a l l o w the t e s t i n g o f s u b j e c t s on the three equat ions g e n e r a l l y used at luminances o f at l e a s t 1 l o g u n i t h i g h e r than those repor ted by Lakowski and p o s s i b l y two l o g u n i t s h i g h e r w i t h an i l l u m i n -ant w h i c h i s h i g h e r i n c o l o r temperature than S a a t 2 8 5 0 ° K . The ins t rument was m o d i f i e d w i t h r e spec t t o i t s source and i t s l i g h t m i x i n g environments i n the f o l l o w i n g manner. The o r i g i n a l source and i t s socket was removed from the lamp-house assembly and the lamphouse and i n t e g r a t i n g chambers were sprayed w i t h a Barium S u l n h i t e p a i n t mix ture which was adapted from t h a t r e p o r t e d by Middeton and. Saunders (1954) . The p a i n t was d i l u t e d i n approx imate ly 1 n a r t acetone and the l i q u i d was then a p p l i e d to the sur faces o f the i n t e -g r a t i n g chamber and the lamphouse. The acetone subsequent ly 70. d r i e d l e a v i n g the barium sulphate - c a r b o n x y m e t h y l - c e l l -u lo se mix ture adhered to the w a l l s . Each o f the i n t e g r a t i n g chambers had one 9 0 ° corner made i n t o a 4 5 ° corner to i n -crease the b r i g h t n e s s o f the l i g h t r each ing the comparison a p e r t u r e s . The lanrahouse was then f i t t e d w i t h a lamo h o l d e r assembly c o n s i s t i n g o f a r a i s e d asbestos n l a t e which had h o l e s d r i l l e d i n i t and p i n s f i t t e d f o r e l e c t r i c a l contac t w i t h the lamp. R e f l e c t o r s were p l a c e d behind the source i n the a x i s o f each o f the two a p e r t u r e s . The source was a 24 v o l t , 150 watt quar tz-ha logen lamp manufactured by P h i l i p s . As i l l u m i n a n t ' A ' i s r e q u i r e d f o r the c o r r e c t c o l o r r e n d i t i o n o f the f i l t e r s at p r e v i o u s l y mentioned l e v e l s (Lakowski 1971) the lamp was run at approx imate ly 13 v o l t s to render the source e f f e c t i v e l y 2850°K« A 24 v o l t t r a n s f o r m e r was used t o r e p l a c e the 12 v o l t model found i n the in s t rument as w e l l . M o n i t o r i n g p lugs were n l a c e d a t the r e a r o f the ins t rument to check the a p p l i e d v o l t a g e a t the socket o f the source . In o r d e r t o c o o l the source and sur rounding f i l t e r s e t c . , an exhaust fan assembly was f i t t e d to the bottom o f the anomal-oscope which f o r c e d a i r through the laraphouse and out the t o p . D u r i n g the e x p e r i m e n t a t i o n , a V a r i a c l i n e t r a n s f o r m e r was used to c o n t r o l the v o l t a g e to the t r a n s f o r m e r , w h i l e a v o l t m e t e r was used to moni tor the source . As can be seen from f i g u r e 12 ( a ) , the l i g h t l e a v i n g both a p e r t u r e s i s 7 1 . SHUTTER SETTING Figure 12a Aperture luminance i s a function of shutter s e t t i n g . 72. Illuminantv A ' 13 volts 2D 3o $o Cc 70 80 SHUTTER SETTING P0 12b Aperture luminance i s a function of shutter setting, 73. q u i t e uni form i n terras o f b r i g h t n e s s . The anomaloscope f i l t e r s used i n t h i s experiment were those w i t h s p e c t r a l c h a r a c t e r i s t i c s as r e p o r t e d by Lakowski (1971) f o r model I . Energy d i s t r i b u t i o n s f o r these f i l t e r s a t the A p e r t u r e m o d i f i e d anomaloscope are presented i n F i g u r e 1 3 . METHOD The twelve v o l u n t e e r s u b j e c t s r e p o r t e d i n Experiment I were dark adapted f o r 10 minutes and then t e s t e d monocular ly ( r i g h t eye) under an approx imat ion o f I l l u m i n a n t T C masked to d e l i v e r 2 . 0 l u x over a 30 x 10 cm a r e a . The observer s wore two l i q u i d f i l t e r s i n f r o n t o f the r i g h t eye i n the manner r e p o r t e d i n Experiment I . The f i l t e r s were p l a c e d i n 4 m u t u a l l y i n c r e a s i n g p a i r s which represented c o n d i t i o n s r a n g i n g from 31 years o l d l e n s p l u s low macular pigment t o extreme l e n s p l u s extreme macular p igment . As V e r r i e s t (1963) n o t e s , the normal sub jec t becomes ' w h o l l y t r i t a n o p i c ' when the i l l u m i n a n c e f a l l s below 0 . 2 l u x . As a p r e c a u t i o n , a l l s u b j e c t s were t e s t e d w i t h the P a n e l D-15 t e s t w i t h o u t the s i m u l a t i o n f i l t e r s a t 0 . 4 2 l u x to determine whether any 4 9 . These measurements were made on the same source used i n t h i s exper iment , which was burned approx imate ly 10$ o f i t s ' b u r n i n g l i f e (50 hours a t 2 4 v o l t s ) be fore these measurements were t a k e n . <Ko 40 *o MO sa Sbo *> <u>, <o& So Loo 2.6 6>o go Too WAVELENGTH (nm) Figure 13 S p e c t r a l c h a r a c t e r i s t i c s o f A n o m a l o s c o p e f i l t e r s ( M o d e l I ) a t a p e r t u r e . 75 . would show ' w h o l l y t r i t a n o p i c ' c h a r a c t e r i s t i c s . Two n e u t r a l d e n s i t y f i l t e r s (combined Y%-21) were used to achieve the r e d u c t i o n i n i l l u m i n a t i o n . A l though some observers made t r i t a n o p i c c o n f u s i o n s , the magnitude o f - e r r o r cannot be seen as l a r g e enough t o c l a s s i f y them as w h o l l y t r i t a n o p i c . The mean-score diagram f o r t h i s c o n t r o l c o n d i t i o n i s p r e -sented i n f i g u r e 14. The n e u t r a l d e n s i t y f i l t e r s p l u s the 50 E x p e r i m e n t a l f i l t e r s were then p l a c e d i n the s u b j e c t s view"^ and each was t e s t e d on the complete 100-hue, P a n e l D-15, and Dvor ine and AO H-R-R pseudoi sochromat ic p l a t e s . Sub-j e c t s were r e q u i r e d t o h o l d the n e u t r a l d e n s i t y f i l t e r throughout the exper iment . The maximum d e n s i t y p a i r o f f i l t e r s (ext l e n s + D macular) r epre sent a r e d u c t i o n o f 27% (Y# ~ 7 3 ) , t h e r e f o r e , the lowest l e v e l o f i l l u m i n a t i o n achieved under the reduced i l l u m i n a t i o n and f i l t e r c o n d i t i o n s i s 0 .31 e q u i v a l e n t l u x . The same observers w i t h t h e i r r e s p e c t i v e l e n s and macular s i m u l a t i n g f i l t e r s (wi thout the N e u t r a l Dens i ty f i l t e r s ) were a l s o t e s ted on the three anomaloscope equat ions at 10 t imes the luminance f o r each equat ion as r e p o r t e d i n Experiment I . A l l above mentioned t e s t s were presented i n a counterba lanced order to e l i m i n a t e 50. Sub jec t s were r e q u i r e d to ho ld the n e u t r a l d e n s i t y f i l t e r s i n f r o n t o f t h e i r r i g h t eye . 76. 77. 78. l e a r n i n g e f f e c t S o A s i n E x p e r i m e n t I, no two s u b j e c t s r e c e i v e d any o f t h e t e s t s i n t h e same o r d e r . RESULTS: The Anoma loscope T a b l e IX shows t h e m i d - p o i n t s and s t a n d a r d d e v i a t i o n s f o r t h e t h r e e e q u a t i o n s a t 10 t i m e s t h e l u m i n a n c e r e p o r t e d i n E x p e r i m e n t I. The re i s a d i s t i n c t d e c r e a s e i n t h e r a n g e s o f b o t h t h e 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 u n d e r t h e ex t reme c o n d i t i o n s a n d , i n a d d i t i o n , t h e m i d -p o i n t s appear , t o be s h i f t e d s l i g h t l y t o w a r d s t h e b l u e f i l t e r v a l u e s o f e a c h p a i r . A s i n t h e p r e v i o u s l y n o t e d f i n d i n g s , t h e m i d - p o i n t s and r a n g e s f o r t h e r e d - g r e e n e q u a t i o n r e m a i n r e s p e c t i v e l y c e n t r a l and s m a l l . The F a r n s w o r t h - M u n s e l l 100-hue T e s t T a b l e X g i v e s t h e mean and s t a n d a r d d e v i a t i o n o f t h e b o x s c o r e s o f t h e 100-hue t e s t p e r f o r m e d u n d e r v e r y l o w i l l u m i n a -t i o n , w i t h t h e e x p e r i m e n t a l f i l t e r s . The i n c r e a s i n g f i l t e r d e n s i t i e s a f f e c t B o x one and B o x t h r e e t h e m o s t , a l t h o u g h a s can be seen by F i g u r e 15 t h e r e a r e h i g h e r r o r s c o r e s a t t h e b e g i n n i n g and end o f e v e r y box i n t h e h i g h d e n s i t y c o n d i t i o n s . 79. 3 U . 5 Figure 15 b 81. > 0.31 Ix Figure 15 c 8 2 . Table IX Anomaloscope Mid-Points and Standard D e v i a t i o n s f o r 10X Luminance of Exp. 1. (Two f i l t e r c o n d i t i o n s . ) •31+A ' 45+D 63+D •" EXT+D Red-Green Equation X 41.0 40 .3 40 .5 39.8 SD 1 .5 1 . 4 0 .5 1 .2 Yellow-Blue Equation X 40.0 47.3 38.8 4 2 . 6 SD 11.3 11 .2 16.1 6.0 Blue-Green Equation X 40.0 40 .3 46.7 44 .8 SD 7.2 6.4 8.5 5.2 83 Table X Means and Standard Devia t ions f o r 100-hue Test ( T w o - F i l t e r C o n d i t i o n s ) 0.3 Lux Box 1 Box 2 Box 3 Box 4 3 I f A X 103.7 70.3 112.0 68.3 SD 40.9 16.7 23.5 22.4 45+B X 107.7 94 .0 119.0 51.3 SD 69.9 33.4 9 .1 30 .3 63+C X 164.0 138.0 163.3 100.0 SD 50.5 28.0 65.0 EXT+D X 159.0 134.3 188.7 88.3 SD 29.7 17 .6 21.9 44.9 84 The Panel D-15 Test As can be noted i n F i g u r e 14, there i s a tendency to confuse the caps i n a manner c h a r a c t e r i s t i c o f the TRITAN Defect. The mean-score diagrams 31-A and EXT-D.indicate the p r o f i l e s of the l e a s t and most dense experimental f i l t e r groups under low i l l u m i n a t i o n . There appears t o be an in c r e a s e i n the TRITAN ERROR between these two c o n d i t i o n s and, as evidenced by the EXT-D p r o f i l e s , a l l observers i n t h i s group p a i r e d caps 7 and 15 , thus i n d i c a t i n g a f a i r l y strong t r i t a n c l a s s i f i c a t i o n . 8 5 . The Pseudoisochromat ic P l a t e s In Experiment I I s u b j e c t s made confus ion mis takes i n both the Dvor ine and AO H-R-R t e s t s . Frequency h i s t o -grams o f these mis takes are presented i n F i g u r e 16. The Dvor ine t e s t seems to be a f f e c t e d most at o l a t e s 9 and 10 , a l though p l a t e s 12 and 13 are a l s o g e n e r a l l y confused . These two p l a t e s seem to be more o f ten confused by observer s wear ing the denser s i m u l a t i o n f i l t e r s . The AO H-R-R t e s t scores show a tendency towards b l u e - y e l l o w c o n f u s i o n . P l a t e s 17 and 18 tend to be weighted toward the t r i t a n c l a s s i f i c a t i o n i n the l o w - d e n s i t y groups and towards the t e t a r t a n c l a s s i f i -c a t i o n i n the h i g h - d e n s i t y group. The author observed t h a t s u b j e c t s g e n e r a l l y made more use o f b r i g h t n e s s and form cues at these l e v e l s o f i l l u m i n a t i o n and i t i s b e l i e v e d t h a t c o r r e c t responses were g iven t o some o f the AO H-R-R p l a t e s by the p e r c e p t i o n o f form and c o n t r a s t r a t h e r than c o l o u r . (The frequency f o r group 63-C i s based on two i n s t e a d o f t h r e e o b s e r v e r s , as one subject d i d n o t complete the AO H-R-R t e s t o r the P a n e l D-15) . 8 6 31+A 45+B 63+C Ext+D j 2 3 \ 4 I -f i H lo ll Iz a * ' 5 li i? '8 c» Jo PLATE NUMBER He 16«l Frequency Histograms f o r Confusion E r r o r s on the AO H-R-R t e s t ( 0.31 Lux) *7 r 31+A r A5*B o c Q) C7" 63+C 3 ExtO I 2 3 4 5 U H k> ii a. 13 if PLATE No. Figure 16 b Frequency Histograms f o r Confusion Errors on the Dvorine Test ( 0.31 Lux) 88 . DISCUSSION I t would appear from the data c o l l e c t e d i n Experiment I that the combinations of l e n s and macular pigment simula-t i o n f i l t e r s produce changes In c o l o r v i s i o n which resemble those changes which have been a t t r i b u t e d t o ageing processes. The c o l o r matching data shows a general widening of the yellow-blue and blue-green matching ranges. The Y e l l o w -Blue equation seems t o be a f f e c t e d most w i t h mid matching p o i n t s not tending to s h i f t towards the blue as one might expect from the experimental f i l t e r c h a r a c t e r i s t i c s . I n -stead there appears to be a general d e s c r i p t i o n of c o l o r matching a b i l i t y . Part of the widening and p o s s i b l e mid-p o i n t s h i f t s can be exp l a i n e d by the f a c t t h a t there are a c t u a l l y fewer d i s c e r n a b l e d i f f e r e n c e s on the yellow side of the equation than there i s on the b l u e . The i n c r e a s e d .'macular pigment' s i m u l a t i o n f i l t e r s seem to a f f e c t the yellow-blue and blue-green equations more than d i d the l e n s f i l t e r s . This f i n d i n g might be i n t e r p r e t e d as i n d i r e c t evidence f o r the e x i s t e n c e of i n c r e a s e s i n macular pigment due t o ageing. Many sub j e c t s accepted matches down to 100% y e l l o w f i l t e r i n the yellow-blue equation (0 on the anomaloscope^ s e t t i n g ) . No one accepted t o t a l l y blue matches. Colour 89. naming o f the anomaloscope ' p r i m a r i e s ' by the observer s w i t h the denser e x p e r i m e n t a l f i l t e r s proved to be q u i t e d i f f i c u l t . The b lue-green equat ion i n p a r t i c u l a r caused n o t a b l e co lour-naming d i f f i c u l t i e s , many observer s ex-changing n o t a b l e co lour-naming d i f f i c u l t i e s , w i t h many observer s exchanging names f o r the pr imary f i l t e r s shown. As g radua l i n c r e a s e s i n the matching ranges can be seen to be a s s o c i a t e d w i t h i n c r e a s e s i n f i l t e r d e n s i t i e s i t i s not improbable t h a t i n the age ing p o p u l a t i o n , i n c r e a s e d matching ranges , a long these same l i n e s c o u l d be produced by g r a d u a l s e l e c t i v e decreases i n o c u l a r t r a n s m i s s i v i t y . However, as can be c l e a r l y seen i n t h i s study these h y p o t h e t i c a l o c u l a r changes do not comple te ly account f o r the extent o f w i d e n i n g o f the matching ranges i n v o l v i n g b l u e l i g h t found i n those age p o p u l a t i o n s which correspond to the f o u r exper imenta l groups mentioned h e r e i n . T h i s p o i n t becomes more ev ident when the c o l o u r d i s c r i m i n a t i o n and confus ion data are n o t e d . F i g u r e 17 g i v e s 100 hue m e a n - p a r t i a l e r r o r scores f o r the f o u r exper imenta l groups under c o n d i t i o n s o f m u t u a l l y i n -c r e a s i n g f i l t e r d e n s i t y p a i r s . Comparing t h i s f i g u r e w i t h V e r r i e s t ' s age data ( F i g . 6a) one may note the correspondence between the two lower d e n s i t y c o n d i t i o n s . However, t h e r e seems to be more e r r o r i n V e r r i e s t ' s data on the i n c r e a s e d age groups than can be accounted f o r by o c u l a r changes a l o n e ; 9 0 . at l e a s t as simulated i n the present study. However, the d i r e c t i o n of change appears to be c o r r e c t . I f r e d u c t i o n s i n the t o t a l amount of l i g h t were made as w e l l , f u r t h e r correspondence might be a t t a i n e d . Experiment I I attempted to combine t h e s imulated reductions i n o c u l a r t r a n s m i s s i v i t y w i t h f u r t h e r r e d u c t i o n s i n i l l u m i n a t i o n i n an i n v e s t i g a t i o n o f c o l o u r v i s i o n . Because the c o l o u r matching data of Experiment I was as a n t i c i p a t e d i t was f e l t t h a t the c o l o r matching task could conceivably be seen as already at a reduced l e v e l . Increases i n the luminance o f the instrument produced two changes i n the response of the experimental observers: 1) Increased luminance decreased the s i z e o f the matching ranges, e s p e c i a l l y the yellow-blue equation. 2) Increased luminance produced a tendency toward s h i f t i n g the mid-point towards the blue 'primary'. This f i n d i n g seems to support V e r r i e s t ' s n o t i o n o f the p o s s i b i l i t y of a 'mesopisation' process t a k i n g place i n the v i s u a l system, at l e a s t from a p h y s i c a l standpoint. The performance o f observers under the increased luminance c o n d i t i o n c l e a r l y shows improvement. I t would seem that the responses become more p r e d i c t a b l e i n the p h y s i c a l terms o f the s i m u l a t i o n f i l t e r c h a r a c t e r i s t i c s under t h i s i n c r e a s e . I t would be i n t e r e s t i n g to see these mid-points and matching ranges measured on ageing observers at the incr e a s e d luminance. 91 I f the ' roe sop i sa t ion ' process was to be seen as a reasonable h y p o t h e s i s , improvement should be noted at the h i g h e r o f the two b r i g h t n e s s l e v e l s . Match ing ranges should decrease b u t , as w e l l , the mid-matching p o i n t should s h i f t towards the b lue ' p r i m a r y ' . - ' 1 Co lour d i s c r i m i n a t i o n data under low i l l u m i n a t i o n and e x p e r i m e n t a l f i l t e r s p o i n t to an ' e a r l y ' c l a s s i f i c a t i o n o f the T r i t a n de fec t and f u r t h e r non-s p e c i f i c degradat ion a f t e r t h a t . The p r o f i l e s o f c o n d i t i o n s under low l u m i n a t i o n are presented i n F i g s . 15 ( a - d ) . A l though V e r r i e s t (1963) r e p o r t s t h a t complete t r i t a n con-f u s i o n s do not occur u n t i l 0.2 L u x ; the observer s i n the pre sent study were s c o r i n g i n a manner which would c l a s s i f y them as T r i t a n a t a minimum o f 0 .31 l u x w i t h the use o f the exper imenta l f i l t e r s . The f i r s t two c o n d i t i o n s appear to be t r i t a n o p i c w h i l e the l a t t e r two apoear a n a r c h i c . T h i s breakdown i n c o l o r d i s c r i m i n a t i o n takes p l a c e at a l e v e l o f 0 .31 l u x and h i g h e r . T h i s would tenuous ly i m p l i c a t e r e d u c t -i o n s i n i l l u m i n a t i o n and s t r o n g l ens -macu la r p igmenta t ion as a p o s s i b l e c o n t r i b u t o r t o a c q u i r e d y e l l o w - b l u e deschromatops ia . The r e s u l t s o f the Pseudoisochromat ic P l a t e s i n Experiment I I 51 . The extent o f t h i s s h i f t cou ld be used as an e s t imate of the s p e c t r a l c h a r a c t e r i s t i c s o f the o c u l a r media . Presumably, the measurement would take i n t o account the r e l a t i v e t h r e s h o l d f o r d i f f e r e n t wavelengths . 9 2 . r a i s e some other i n t e r e s t i n g questions. With i n c r e a s i n g f i l t e r d e n s i t y there are increased e r r o r scores on both the Dvorine and AO H-R-R t e s t s . The f o u r most common confusion e r r o r s as seen i n F i g u r e 16 are P l a t e s 17 and 18 o f the AO H-R-R and P l a t e s 9 and 10 of the Dvorine. I t i s f e l t t h a t the experimental c o n d i t i o n s employed i n t h i s s e c t i o n a f f e c t not only c o l o r d i s c r i m i n a t i o n but p a t t e r n r e c o g n i t i o n as w e l l . In random p r e s e n t a t i o n s of the Dvorine p l a t e s f o r example, the ' h e a v i l y pigmented' observer might s t i l l be able to d i f f e r e n c e s i n c o l o u r but not i d e n t i f y the f i g u r e . As noted e a r l i e r , the AO H-R-R t e s t e d i t i o n s used i n t h i s study showed some Darts of f i g u r e s which were s l i g h t l y d i s c e r n a b l e by form c o n t r a s t s w i t h the surround. The set number of geometrical f i g u r e s used i n c r e a s e s the observer's chances of c o r r e c t guessing; f o r example a s t r a i g h t l i n e p e r c e i v e d i n the P l a t e u s u a l l y means e i t h e r a t r i a n g l e or a square e t c . I t would seem from the obser-v a t i o n s of the author t h a t responding to a stimulus i n a manner which r e q u i r e s some form of v e r b a l r e c o g n i t i o n o f the meaningfulness of the stimulus i s c o n c e p t u a l l y more d i f f i c u l t than simple manipulation of the stimulus para-meters as i n the 100 hue t e s t . Many subjects 'saw' d i f f e r -ences at the reduced i l l u m i n a t i o n l e v e l s but were unable to s t a t e what these d i f f e r e n c e s were. Of course anything, but K> M J O 6b » D ?0 8» fV\ , ^ to ZO X> 40 So to ?B SD 63*C QXt+D mean partial error 100-HUE FiqiirG 1 7 100 hue p r o f i l e f o r 4 mutually increasing p a i r s of simulation f i l t e r s 100 lux. 94. but the c o r r e c t f i g u r e response i s t r e a t e d as a mistake i n the PIC t e s t s and t h e r e f o r e some p o t e n t i a l l y u s e f u l i n f o r m a t i o n i s l o s t as a r e s u l t of t h i s s c o r i n g procedure. 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Simulation F i l t e r C h a r a c t e r i s t i c s AoDendix A Optical Density vs. Wavelength t s i n g l e c e l l . conditions) A B C D 31 45 63 EXT 390 .1 .14 . .25 .34 .07 .18 .84 1.24 400 .13 .18 .3 .4 .07 .17 .81 1.21 410 .15 .20 .35 .48 .06 .16 .76 1.15 420 . 16 .28 .42 .58 .06 .14 .66 1.05 430 .18 .33 .48 .64 .05 .12 .48 .9 440 .18 .34 .51 .72 .04 .10 .32 .84 450 .19 .39 .59 .78 .03 .08 .22 . 6 460 .19 .38 .59 .76 .02 .06 .12 .44 470 .16 .36 .5 .68 .01 .05 .09 .34 480 .16 .36 .49 .63 .01 .04 .08 . 2 6 490 .14 .32 .42 .60 .01 .04 .06 .13 500 .09 .22 .23 . 3 6 .01 .04 .05 . 16 510 .05 .10 .14 .18 .01 .03 .05 .12 520 .03 .05 .07 .08 .01 .02 .05 .10 530 .02 .02 .03 .03 .01 .01 .05 .09 540 .02 .02 .02 .02 .01 .01 .05 .08 550 .01 .02 .01 .01 .01 .01 .05 .08 Appendix A cont inued (two c e l l c o n d i t i o n s ) A-31 A-45 A-63 A-EXT B-31 B-45 B-63 B-EXT 390 .17 .28 94 • . 1.34 .21 .32 .98 1.38 400 .20 .30 .94 1.34 .25 .35 .99 1.39 410 .21 .31 .91 1.30 .26 .36 . 96 1.35 420 .22 .30 .82 1.21 .34 .42 .94 1.33 430 .23 .30 .66 1.08 .38 .45 .31 1 .23 440 .22 .28 .50 1.03 .38 .44 .66 1.12 450 .22 .27 .41 .79 .41 .47 .51 .99 460 .21 .25 .31 .63 .40 .44 .50 .82 470 .17 .22 .25 .50 .37 .41 .45 .70 480 .17 .20 .24 .42 .33 .40 .44 .62 490 .15 .18 .20 .32 .33 .36 .38 .50 500 .10 .13 .14 .25 .23 .26 .27 .38 510 .06 .08 .10 .17 .11 .13 .15 .22 520 . 0 4 .05 .08 .13 .06 .09 .10 .15 530 .03 .03 .08 .11 .03 .04 .08 .11 540 .03 .03 .07 .10 .03 .03 .07 .10 550 .02 .02 . 06 .09 .02 .02 .07 .09 Appendix A cont'd C-31 C-45 390 .32 .43 400 .37 .47 410 .51 .51 420 .48 .56 430 .53 .60 440 .55 .61 450 .62 .67 460 . 61 .65 ,470 .51 .55 480 .50 • .53 490 .43 .46 500 .29 .32 510 .15 .17 520 .08 .10 530 .04 .04 540 .03 .03 550 .02 .02 C-63 C-EXT D - 3 0 1.00 . 1.49 .41 1.11 1.51 .47 1.11 1.50 .54 1.08 1.47 .64 .96 1.38 .69 .83 1.35 .76 .81 1.19 .81 .71 1.03 .78 .59 .84 .69 .57 .75 .69 .48 .60 .61 .33 .44 .37 .19 . 26 .19 .12 .17 .09 .08 .12 .04 .07 .10 .03 .06 .09 .02 D - 4 5 D - 6 3 D - E X T .52 1.18 1.58 .57 1.21 1 .61 .64 1.24 1.63 .72 1.24 1.63 .76 1.12 1.54 .82 1.04 1 .54 . 8 6 1.00 1.38 .82 .88 1.20 .73 .77 1.02 .72 .74 .94 .64 . 6 6 .78 .40 .41 .52 .21 .23 .30 .10 .13 .18 .04 .08 .12 .03 .07 .10 .02 . 06 .09 Appendix A cont'd C-31 C-45 390 .32 .43 400 .37 .47 410 .51 .51 420 .48 .56 430 .53 .60 440 .55 .61 450 .62 .67 460 . 61 .65 470 .51 .55 480 .50 .53 490 .43 .46 500 .29 .32 510 .15 .17 520 .08 .10 530 .04 .04 540 .03 .03 550 .02 .02 C-63 -C-EXT D-30 1.00 1.49 .41 1.11 1.51 .47 1.11 1.50 .54 1.08 1.47 .64 .96 1.38 .69 .83 1.35 .76 . B l 1.19 .81 .71 1.03 .78 .59 .84 .69 .57 .75 .69 .48 .60 .61 .33 .44 .37 .19 . 26 .19 .12 .17 .09 .08 .12 .04 .07 .10 .03 .06 .09 .02 D-45 D-63 D-EXT .52 1.13 1.58 .57 1.21 1.61 .64 1 .24 1.63 .72 1 .24 1.63 .76 1.12 1.54 .82 1.04 1.54 .86 1.00 1.38 .82 .88 1.20 .73 .77 1.02 .72 .74 .94 .64 . 66 .78 .40 .41 .52 .21 .23 .30 .10 .13 .18 .04 .08 .12 .03 .07 .10 .02 .06 .09 

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