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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 C o l u m b i a , 1971  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS  i n t h e Department of  Psychology  We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e required standard  THE UNIVERSITY OF BRITISH COLUMBIA September, 1972  In p r e s e n t i n g an  advanced degree at  the I  this thesis  Library  in p a r t i a l f u l f i l m e n t o f  the U n i v e r s i t y  of  British  s h a l l make i t f r e e l y a v a i l a b l e  for  the  requirements  Columbia, I agree r e f e r e n c e and  f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f  f o r s c h o l a r l y purposes may  the Head o f my  by  his  of  t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not  written  representatives.  be granted by  It i s understood that  permission.  Department  of  The U n i v e r s i t y o f B r i t i s h Vancouver 8, Canada  Columbia  be  for  that,  study.  this  thesis;  Department or  copying or  publication  allowed without  my  r  i ABSTRACT Two  experiments  i n v e s t i g a t e d the e f f e c t s o f 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 i m u l a t i o n f i l t e r s a p p r o x i m a t i n g l e n s and m a c u l a r pigment changes were c o n s t r u c t e d on the b a s i s o f o r e v i o u s gations.  investi-  E x p e r i m e n t I i n v e s t i g a t e d the e f f e c t s o f t h e s e  f i l t e r s on young, n o r m a l s u b j e c t p e r f o r m a n c e .  S h i f t s were  found i n the d i r e c t i o n o f a g e i n g p o p u l a t i o n s but n o t g r e a t as i s r e q u i r e d .  as  Experiment I I i n v e s t i g a t e d the  additional effect of reductions i n illumination. e x p e r i m e n t a l m a n i p u l a t i o n s t o g e t h e r account  The  two  for senile  d e c r e a s e s i n d i s c r i m i n a t i o n a t s l i g h t l y h i g h e r l e v e l s than previously reported.  ii  TABLE OF CONTENTS Page Abstract . . . . . . . . • » . . . . • . . « . .  ...,.......»!  L i s t of Tables  i i i  L i s t of Figures  iv  Acknowledgments  vi  Introduction Experiment  ..  ..1  I  40  Apparatus  40  Method  52  Re s u i t s Experiment  .....54  II  Modifications Anomaloscope  67 o f the  Pickford-Nicholson  6$  Method  73  Results  7o  Discussion.  .o#  Bibliography Appendix  95 ...<>  104  i i i  LIST OF TABLES Table  *  Page  1.  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 • 14  2.  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 ... . ..15  3<>  B r i g h t n e s s V a l u e s o f t h e L e a s t and Most Dense E x p e r i m e n t a l S i m u l a t i o n 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  .,..51  5.  Anomaloscope M i d - P o i n t s and Standard tions f o r the Control Conditions . *  6.  Anomaloscope 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 S i n g l e F i l t e r Conditions ...58"  7.  Anomaloscope M i d - P o i n t s and Standard D e v i ations f o r Two-filter Conditions  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)  9.  Anomaloscope M i d - P o i n t s and Standard D e v i a t i o n s f o r 10X Luminance o f Exp. 1 . . . . . 8 2  Devia-  1 0 . Means and S t a n d a r d D e v i a t i o n s f o r 100-hue Test  57  59 64  83  iv LIST OF FIGURES FIGURE  Page  1,  S p e c t r a l Absorption o f Human Lenses as a Function o f age........ .. •4  2.  Estimates o f S c a t t e r i n the Human Eye as a Function o f age . •. ...6  3a  Wald's (1945) Estimate o f the "macular pigment" . 10 Ishak's (1953) Estimate o f the "macular pigment .11  3b 3c  Ruddock's ( I 9 6 0 Estimate o f the "macular pigment" 12  3d  Bone and Sparrock's (1971) 3 d e n s i t i e s o f estimated "macular pigment" .......16  3e  Bone and Sparrock's (1971) Average estimate of the "macular pigment" ...............17  3f  Estimate o f the macular pigment by N a y l o r 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 . . . 3 3  6.  Mean P a r t i a l E r r o r Score P l o t s  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 o f Said and V/eale's lens estimates f o r 4 ages .39  9.  Absorption C h a r a c t e r i s t i c s o f the Simulated Lens F i l t e r s .........43  ....34  V  FIGURE  Page  10.  Absorption Characteristics macular pigment f i l t e r s  11a  Absorption Characteristics of Macular 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 values ...  ....47  Absorption Characteristics of macular S i m u l a t i o n f i l t e r ' B » and e x p e r i m e n t a l values ....  ....43  lib  11c  Absorption Characteristics Simulation values • •  lid  filter  •C*  and  of  filter  "d"  and  the  Simulated 46  lens  lens  Macular  experimental  lens  .......49  Absorption Characteristics Simulation values  I  of  of  Macular  experimental  lens  ........50  12a  Aperture setting  luminance  as  a  function  of  shutter 71  12b  Aperture setting  luminance  is  a  function  of  shutter 72  13.  Spectral  characteristics  filters  (Model  I)  at  of  Anomaloscope  oo..»74  aperture  14a  P a n e l D-15  Mean  Scores  76  14b  P a n e l D-15  Mean  Scores  77  15a  100-hue  Profiles  79  15b  n  n  n  £0  15c  n  n  n  gl  16a  Frequency Histograms on  16b  100  the  Dvorine  hue  pairs  Confusion  Errors  AO H - R - R t e s t  Frequency Histograms on  17.  the  for  of  profile  86 for  Confusion  Errors  Test for  simulation  37 4 mutually filters  100  increasing lux  ......93  vi  ACKNOWLEDGMENTS The a u t h o r would l i k e t o e x p r e s s h i s g r a t i t u d e t o many p e o p l e who c o n t r i b u t e d  t o t h e development o f t h i s  thesis: Keith Oliver S h e i l a Campbell Susan B r i d g e The o b s e r v e r s who p a t i e n t l y s a t t h r o u g h hours o f testing. F i n a l l y , t h e a u t h o r would l i k e t o thank Dr. R. L a k o w s k i 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 and  aim o f t h e p r e s e n t  extraneously  investigation i s to physically  s i m u l a t e changes i n t h e 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 human c r y s t a l l i n e l e n s and macula l u t e a and t o l o o k a t t h e 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 m a t c h i n g and p o s s i b l y , c o l o r confusion.  I n a d d i t i o n , t h e e f f e c t o f r e d u c t i o n s and  i n c r 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 p u r p o r t e d t o measure t h e a f o r e m e n t i o n e d c o l o r v i s i o n p a r a m e t e r s w i l l be examined i n an attempt t o e s t i m a t e  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 population. I n o r d e r f o r t h e r a d i a t i o n man c a l l s l i g h t t o be recognized and  as such i t must f i r s t t r a n s v e r s e t h e o c u l a r media  r e t i n a l l a t t i c e t o e x c i t e t h e end-organs o r p h o t o -  receptors.  From t h e a i r - c o r n e a l i n t e r f a c e t o i t s u l t i m a t e  a b s o r p t i o n and t r a n s d u c t i o n i n t o n e r v e i m p u l s e s , r e f r a c t e d and a t t e n u a t e d . achieved  light i s  The l a t t e r , a t t e n u a t i o n , can be  t h r o u g h t h e a b s o r p t i o n o f l i g h t by m a t t e r o r t h e  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 t h e 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 b e , i n terms o f  w a v e - l e n g t h , s e l e c t i v e o r n o n - s e l e c t i v e depending upon t h e c h a r a c t e r i s t i c s o f t h e media w h i c h t h e r a y p a s s e s t h r o u g h . I n t h e human e y e , t h e two most w i d e l y s t u d i e d o f t h e s e media are t h e c r y s t a l l i n e l e n s and t h e macula l u t e a r e g i o n o f t h e  1 central  retina.  CRYSTALLINE LENS The  t h i r d o p t i c media w h i c h l i g h t must p a s s t h r o u g h on  i t s way t o t h e r e t i n a l p h o t o r e c e p t o r s lens.  i s the c r y s t a l l i n e  I n t h e n o r m a l eye t h e l e n s i s a b i c o n v e x ,  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 o f  60-70$ w a t e r ,  6fo  f a t and r e l a t i v e l y more p r o t e i n t h a n any  o t h e r 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 w h i c h 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 n o t m e l a n i n as p r e v i o u s l y t h o u g h t . transmission  Spectral  c h a r a c t e r i s t i c s f o r t h e human o c u l a r media were  f i r s t a t t e m p t e d by A s c h k i n a s s  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 t h e v i s i b l e spectrum was entered f a r red.  o n l y t o t h e e x t e n t o f 670 nanometers (nm), i n t h e H i s c o n c l u s i o n was t h a t t h e o c u l a r media resembled  w a t e r i n terms o f i t s a b s o r p t i o n about 1938,  characteristics.  Up u n t i l  t h i s was t h e g e n e r a l consensus when L u d v i g h and  1.  Boynton and C l a r k e (1964) p o i n t o u t t h a t t h e c o r n e a l s t r u c t u r e accounts f o r a reasonably large p r o p o r t i o n o f scatter.  2.  McEwan (1959, pp 146) s t a t e s t h a t t h e urochrome substan found i n t h e l e n s i s p r o b a b l y a n o n - s n e c i f i c d e g r a d a t i o n product o f p r o t e i n . This f i n d i n g i s consistent with the finding that the lens structure i sprotein r i c h .  3.  As c i t e d by L u d v i g h and McCarthy (1938")  -3McCarthy (1938) p u b l i s h e d e s t i m a t e s and  o f t h e o c u l a r media  reported that " i t i s t h e l e n s which accounts f o r the  major p a r t o f t h e s e l e c t i v e a b s o r p t i o n visible  spectrum".' ' 4  o f t h e eye i n t h e  U n f o r t u n a t e l y , L u d v i g h and McCarthy  d i d n o t p u b l i s h r e s u l t s on t h e i n d i v i d u a l components o f t h e o c u l a r media and i t was n o t u n t i l 1945 t h a t Wald 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 .  published  Weale (1954)  o b j e c t s t o V/ald's (1945) f i n d i n g s on t h e b a s i s t h a t t h e l e n s e s may have reached an " u n p h y s i o l o g i c a l degree o f c l o u d i n e s s " ^ b y t h e t i m e t h e 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 a b s o r p t i o n c u r v e s w h i c h were based on two melanotomous eyes and t h e r e f o r e h i s d a t a 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-  h e n s i v e measurements made i n s i t u on a c r o s s s e c t i o n o f agegroups was made by S a i d and Weale (1959).  Using a technique  by w h i c h comparisons o f t h e s m a l l b u t measurable amounts o f l i g h t r e f l e c t e d a t t h e v a r i o u s media i n t e r f a c e s , o t h e r w i s e known a s P u r k i n j e images, t h e a u t h o r s d e r i v e d  lenticular  spectral absorption  c u r v e s a t s i x ages.  shown i n F i g u r e 1.  McEwan (1959) s u g g e s t s t h a t t h e pigment  may i n c r e a s e i n c o n c e n t r a t i o n w i t h age.  Their results are M e l l e r i o (1971)  4.  i b i d , pp 48  5.  S a i d 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 l e n s e s . S a i d and Weale (1959) r e p o r t t h a t F. Salomon (1950) made some o f t h e f i r s t i n v i v o measurements.  - 4 -  WAVELENGTH (nm)  FIGUTG  1  S p e c t r a l A b s o r p t i o n o f Human Lenses as a f u n c t i o n o f age. from S a i d and Weale ( 1 9 5 9 ) .  -5-  s u g g e s t s 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 t h r o u g h t h e 7 by a b s o r p t i o n and s c a t t e r  lens  i s due t o a " h y p o t h e t i c a l  a b s o r b i n g p i g m e n t " , but because t h e 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 c o n s t a n t between ages 20 and 60, senile yellowing effect thickness.  is  seen as due t o i n c r e a s e s  the  i n lens  A l t h o u g h i n g e n e r a 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 m i d d l e aged l e n s e s o n l y and n o t o l d l e n s e s w h i c h 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 t h e l e n s  ageing,  o c c u r r i n g w i t h o u t any accompanying changes i n t h e r e c e p t o r a l r e s p o n s e , can s u c c e s s f u l l y p r e d i c t t h e e f f e c t o f age upon g color v i s i o n " .  He i n d i c a t e s t h a t t h e s c a t t e r i n g e f f e c t  c r e a s e s 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  is  ogous t o t h e d a t a o b t a i n e d f o r c o l o r m a t c h i n g d a t a .  in-  analRuddock  (1964) f u r t h e r a r g u e s t h e s c a t t e r i n g i n c r e a s e w i t h age would h e l p t o a c c o u n t f o r t h e l o s s o f v i s u a l a c u i t y w i t h age as well. I n c r e a s e s i n s c a t t e r due t o age e f f e c t s a r e p r e s e n t e d 9 in Figure 2.  From t h e 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 t h e 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 t o be s c a t t e r e d . The S h o r t w a v e l e n g t h s t e n d t o produce more s c a t t e r t h a n do longer ones, (see R i g g s , 1965» pp 24) M e l l e r i o does n o t s t a t e t h e 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 of l i g h t . 8.  Ruddock (1964) p p .  9o  ibid.  p p . 137  191  ( i s an adaoted  figure)  -6-  WAVELEN6TH (nm)  Figure 2  E s t i m a t e s o f S c a t t e r i n t h e Human Eye a s a F u n c t i o n o f Age. adapted from Ruddock (1964)  -7-  the c o l o r changes and t h e t r a n s p a r e n c y  changes a t d i f f e r e n t  w a v e l e n g t h s ) and l i k e a s c a t t e r i n g f i l t e r o f t h e R a y l e i g h - t y p e , a t t e n u a t i n g t h e short-wave end o f t h e s p e c t r u m . ^ Ruddock (1972) r e p o r t s t h a t a c c o r d i n g t o Vos and Boogaard (1963) l i g h t s c a t t e r i n g ' c e n t e r s ' a r e n o t u n i f o r m l y  distri-  b u t e d t h r o u g h o u t t h e l e 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 o f 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 a r e a around and i n c l u d i n g t h e  f o v e a c e n t r a l i s o f about 3-5 mm i n d i a m e t e r .  According t o  I s h a k (1952) t h e macula l u t e a was f i r s t o b s e r v e d by B u z z i i n 1682 and i n d e p e n d e n t l y  a g a i n by Soemmering i n 1795.  Soemmer-  r i n g i s r e p o r t e d t o have o b s e r v e d t h e "macula pigment""^ ( a c c o r d i n g t o Ruddock (1964)) and G u l l s t r a n d (1906) i s reported  (by t h e same a u t h o r ) t o have i d e n t i f i e d t h e pigment  as a c a r o t e n o l d a n d , f u r t h e r , s t a t e d t h a t i t was a p o s t mortem e f f e c t . viewpoint  H a r t r i d g e , (1950) h e l d t h e "post-mortem e f f e c t "  as w e l l .  A l t h o u g h some w r i t e r s do n o t f u l l y  i t s e x i s t e n c e i n v i v o (Trezona,  accept  1970) t h e r e i s a m a j o r i t y o f  10.  Cooper and Robson (1969) p o i n t t o t h e 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 w h i c h would add t o t h e g e n e r a l ' y e l l o w n e s s ' o f the l e n s c o l o r .  11.  T h i s 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 ambigu i t i e s i n t h e t h e s i s t e x t . Soemmerring may have, i n f a c t , o n l y o b s e r v e d t h e macula l u t e a i n v i t r o a s t h e ophthalmoscope was i n v e n t e d by H e l m h o l t z a t a l a t e r d a t e .  -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 t h e v a s c u l a r r e t i n a l the f o v e a l r e g i o n appeared i n a d e q u a t e  i n and o f  system  at  itself,  prompted D a r t n a l l and Thompson (1949) t o i m p l i c a t e t h e m a c u l a r pigment i n an o x y g e n - t r a n s p o r t photoreceptors.  system t o t h e f o v e a l  Denton and P i r e n n e (1950) and Wald (1967)  s u g g e s t s t h a t t h e m a c u l a r pigment i s an a d a p t i v e mechanism which serves to minimize chromatic 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 t h e h i g h e s t a c u i t y ) by a b s o r b i n g much o f the short wavelength l i g h t .  Although the lens absorbs  short  w a v e l e n g t h s as w e l l , t h e m a c u l a r pigment ' p e a k s ' i n t h e 460 nm range whereas t h e l e n t i c u l a r pigment a b s o r b s m a x i m a l l y 12 c l o s e r t o 400 nm.  B a s i c a l l y , two major t y p e s 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 t h e e x i s t e n c e o f t h e m a c u l a r pigment in (a)  vivo. The comparison o f f o v e a l and p a r a - f o v e a l  sensitivities, (b)  spectral  and;  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  Haidinger Brushes.  12.  W y s z e c k i and S t i l e s (1967) use 403 nm as t h e i r r e f e r e n c e p o i n t f o r t h e l e n s a b s o r p t i o n and 455 nm f o r t h e m a c u l a r 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 t h e pigment from a s m a l l number o f  human maculas and s u b s e q u e n t l y i d e n t i f i e d i t a s "a h y d r o x y carotenoid or xanthophyll, 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 xanthophyll i t s e l f " . '  V/ald f u r t h e r o b t a i n e d p s y c h o p h y s i c a l  d a t a based on comparisons  o f f o v e a l and p a r a f o v e a l 8 °  spectral  s e n s i t i v i t y and a d j u s t e d t h e o p t i c a l d e n s i t y o f t h e m a c u l a r xanthophyll to f i tt h i s d a t a . ^  The e s t i m a t e o f t h e m a c u l a r  pigment from b o t h t h e s e f i n d i n g s i s p r e s e n t e d i n F i g u r e 3 ( a ) . Ishak  ( 1 9 5 2 ) i n v e s t i g a t e d t h e macular pigment d e n s i t i e s o f 1 5  E g y p t i a n s u b j e c t s and n o t e d t h a t t h e i r average v a l u e s were h i g h e r than t h o s e r e p o r t e d by B r i t i s h , American and German observers.  H i s r e s u l t s and t h e i n v e s t i g a t i o n s o f o t h e r s  r e p o r t e d by him a r e p r e s e n t i n F i g u r e 3 ( b ) . Ruddock ( 1 9 6 3 ) p u b l i s h e d e s t i m a t e d m a c u l a r pigment d e n s i t i e s o f two o b s e r vers.  H i s e s t i m a t e 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 n o t e d t h a t h i s  second o b s e r v e r has almost no m a c u l a r pigment a c c o r d i n g t o t h e d a t a p r e s e n t e d , y e t (Ruddock 1 9 7 2 ( b ) ) fundus r e f l e c t o metry d a t a e s t i m a t e s t h e d e n s i t i e s t o be e q u a l i n b o t h 13.  Wald ( 1 9 4 5 ) P P .  657  14.  Wald ( 1 9 4 9 ) t r i e d t o i n t e r p r e t t h e i n c r e a s e d p e r i p h e r a l s e n s i t i v i t y t o t h e b l u e - e n d o f t h e spectrum a s t h e absence o f macular p i g m e n t a t i o n . Weale ( 1 9 5 3 ) suggests however, t h a t t h e n o t e d i n c r e a s e i n b l u e - s e n s i t i v i t y may be due t o improvements i n t h e s e n s i t i v i t y o f t h e peripheral photo-receptors.  -10  •  ViSuftL E s r i m f i T E  "tvxiaUao  p  XHtiikflnyll  0.9 as o.7  0.6 05  0.3 03 0.1  o Coo 45c  350  $00  £50  WAVELENGTH (nm)  niirP yui ^  3 fl  v^u  V7ald's (1945) E s t i m a t e o f t h e n pigment". m  a  c  u  l  a  r  -11-  WAVELENGTH (nm)  UTG  3 b  Ishak's (1953) Estimate of the •macular pigment'*  -12-  FJQUre 3C J  Ruddock's (1964) Estimate of the 'macular pigment'.  observers. hensive  Bone and Soarrock  (1971) r e p o r t a r a t h e r compre-  study w h i c h i n c l u d e m a c u l a r pigment e s t i m a t e s o f 49  observers.  T h e i r comparisons a r e i n c l u d e d i n F i g u r e 3(d -i e ) .  Groups c o n t r a s t e d i n t h e l a t t e r study i n c l u d e d t h o s e o f T a b l e I . From t h e i r i n v e s t i g a t i o n i t a p p e a r s a s i f d a r k l y pigmented p e o p l e s t e n d t o have s l i g h t l y more m a c u l a r pigment  15 than do l i g h t l y pigmented B.  people.  ENTOPTIC COLOR PERCEPTION OF MAXWELL'S SPOT AND THE HAIDINGER BRUSHES. The  second major method o f e s t i m a t i n g t h e m a c u l a r p i g -  ment i s w i t h t h e use o f e n t o p t i c phenomena. a subject views a uniform f i e l d continuous  I f f o r example  (which i s i l l u m i n a t e d by a  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  f i l t e r and a p u r p l e g e l a t i n f i l t e r  grey  ( t r a n s m i t t i n g only near  the short-wave ( b l u e - v i o l e t ) and t h e long-wave ( r e d ) 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°  This  was  about t h e f i x a t i o n p o i n t o f r e s p e c t .  spot  f i r s t d e s c r i b e d b y M a x w e l l who i n t e r p r e t e d i t a s due t o  d e c r e a s e d e f f e c t i v e n e s s o f b l u e l i g h t i n s t i m u l a t i n g t h e cones o f t h e f o v e a l r e g i o n because i f i t s a b s o r p t i o n by t h e m a c u l a r pigment. 15.  One n o t a b l e e x c e p t i o n as seen i n T a b l e I i s o f t h e r e d h a i r e d v e r s u s n o n - r e d - h a i r e d comparison. The named authors a r e reportedly 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 o f t h e s m a l l number o f s u b j e c t s .  -14Table  I for Different  V a r i a t i o n s i n Pigment Wavelength  Groups  Density- (from Bone and S p a r r o c k ,  East Indian  Non-East Indian  Red h a i r e d  1971) Non-red haired  400  0.49  0.35  0.54  0.34  410  0.52  0.38  0.57  0.36  420  0.53  0.40  0.62  0.39  430  0.59  0.44  0.66  0.43  440  0.63  0.43  0.71  0.46  450  0.68  0.52  0.74  0.50  460  0.69  0.52  0.73  0.51  470  0.64  0.49  0.68  0.48  480  0.56  0.44  0.63  0.43  490  0.46  0.36  0.52  0.35  500  0.36  0.28  0.41  0.27  510  0.29  0.22  0.32  0.21  520  0.21  0.16  0.24  0.16  530  0.16  0.13  0.19  0.12  540  0.12  0.10  0.14  0.09  550  0.08  0.07  0.09  0.07  -15Table  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 ivelength (nm) 400  Age Over 30  0.34  Soarrocl Age Under' 1 9 7 1 ) 22 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  -16-  Figure 3d  Bone and Sparrock'.y( 1971) 3 d e n s i t i e s o f estimated 'macular pigment'.  -17-  loo _  5&?  WAVELENGTH (nm)  Figure 3 e  Bone and Spar-rock's (1971) Average estimate o f the 'macular pigment'.  -18Judd (1953) r e p o r t e d : A c c o r d i n g t o t h e assumed three-components t h e o r y t h e m a c u l a r pigment s h o u l d be v i s i b l e e n t o p t i c a l l y by means o f t h e w a l l s p u r p l e f i l t e r and a n o n - r s e l e c t i v e g r e y f i l t e r o f about one p e r c e n t t r a n s m i t t a n c e used a l t e r n a t e l y even though t h e r e i s no d i f f e r e n c e between macular and e x t r a - m a c u l a r r e c e p t o r s e i t h e r a s t o Dooulation d e n s i t y , as suggested by W a l l s , o r as t o s p e c t r a l s e n s i t i v i t y a p a r t from d i f f e r e n c e i n t r o d u c e d by t h e m a c u l a r pigment i t s e l f . . . and: To e x p l a i n M a x w e l l ' s S p o t , t h e r e i s no need t o assume t h e existence o f 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 o r p o p u l a t i o n d e n s i t i e s w h i c h a r e d i f f e r e n t from t h o s e o f the e x t r a - m a c u l a r r e c e p t o r s . On t h e o t h e r hand, t h i s a n a l y s i s l e a v e s open t h e p o s s i b i l i t y t h a t such m a c u l a r 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 t o M a x w e l l ' s S p o t . " 1  A l t h o u g h Judd d i d h i s a n a l y s i s on t h e s t a n d a r d o b s e r v e r (which i s based on r e a l o b s e r v e r s b u t n o t 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 t h e M a x w e l l i a n s p o t i s an e n t o p t i c perception o f the macular p i g m e n t . ^  Judd used Wald's (1945)  e s t i m a t e s o f t h e m a c u l a r pigment f o r h i s a n a l y s i s and d i d n o t estimate a density with 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 o u t t h a t : the M a x w e l l - s p o t e f f e c t i s a s s o c i a t e d w i t h w a v e l e n g t h s a t w h i c h t h e m a c u l a r pigment i s e x p e c t e d t o a b s o r b . I t i s n o t seen by o b s e r v e r s who, from c o n s i d e r a t i o n o f c o l o r matches i n t h e f o v e a and p a r a f o v e a , would be c l a s s i f i e d as nonpigmented. When a p l a n e p o l a r i z e r i s r o t a t e d b e f o r e t h e o b s e r v e r ' s e y e , t h e maxwell spot b r e a k s up i n t o a form t y p i c a l o f H a i d i n g e r ' s b r u s h e s . The b r u s h e s ... a r e s i m i l a r i n c o l o r t o t h e u s u a l M a x w e l l s p o t , whereas t h e i n t e r v e n i n g space a p p e a r s t h e same as t h e s u r r o u n d i n g f i e l d . This breakdown o f 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 s u p p o r t s  16.  Judd (1953) PP. 20  17.  This i s a confirmation of Maxwell's own report to Judd (1953).  according  -19t h e t h e o r y t h a t t h e n o n u n i f o r m i t y i t s e l f , and hence t h e a s s o c i a t e d changes i n c o l o r m a t c h i n g , i s due t o l i g h t l o s s e s w h i c h o c c u r 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 M a x w e l l - s p o t and H a i d i n g e r brush phenomena,18 Trezona (1970) f e e l s  t h a t t h e m a c u l a r pigment i s n o t  needed t o e x p l a i n M a x w e l l ' s s p o t : L i g h t i s absorbed by t h e r o d s most e f f e c t i v e l y i n t h e b l u e g r e e n , t h i s g i v e s a b l u e s e n s a t i o n i n the p e r i p h e r y and t h e f o v e a appears y e l l o w s i m u l t a n e o u s c o n t r a s t . 1 " In f a c t T r e z o n a ' s argument e x t e n d s t o p r a c t i c a l l y a l l o f the evidence i n support of the macular pigment.  The  H a i d i n g e r " b r u s h e s " o r H a i d i n g e r e f f e c t was used t o  estimate  t h e m a c u l a r pigment e x t a n t 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 20  t h a n c o n t a i n s t h e m a c u l a r pigment  and t h u s t h e i r  a r e open t o c r i t i c i s m a l o n g t h e s e l i n e s .  field results  N a y l o r and S t a n -  w o r t h (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 t h e ?1 effect.  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  t h e m a c u l a r pigment was r e s p o n s i b l e f o r t h e 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 t h e p r e m i s e 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 d a t a b e s t f i t t h e f o r m e r i n t e r p r e t a t i o n . They c o n c l u d e d 1 8 . Ruddock (1965) p p . 1180 1 9 . T r e z o n a (1970) p p . 330 2 0 . o r as an a l t e r n a t i v e h y p o t h e s i s would have i t , t h e orientation of blue-receotors 21.  D e V r i e s e t . a l . (1953) d i s c u s s Haidinger effect.  the r e a s o n i n g f o r t h e  22.  I n an e a r l i e r p a p e r , Stanworth and N a y l o r (1950) s t a t e d t h a t t h e l a t t e r was t h e cause o f H a i d i n g e r * s e f f e c t .  -20t h a t t h e H a i d i n g e r e f f e c t was caused a b s o r p t i o n o f l i g h t by t h e o r i e n t e d m a c u l a r pigment.  Their estimate o f the  o r i e n t e d pigment i s i n F i g u r e 3 ( f ) . state tenuously  N a y l o r and S t a n w o r t h  t h a t t h e i r m a c u l a r pigment curve  corresponds  with that o f Xanthophyll but that 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 c o n s i d e r e d  c e r t a i n because o f an a d d i t i o n a l m a x i -  mum a b s o r p t i o n a t 515 mm and a n o m a l i e s i n X a n t h o p h y l l ' s peak a b s o r p t i o n 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 . ^  The m a c u l a r  pigment has a l s o been i m p l i c a t e d i n t h e H a i d i n g e r  brush  2  e f f e c t by Sloan and Naquin (1955).  Because o f t h e d i f f i c u l t y  i n i n t e r p r e t i n g t h e r e s u l t s , W y s z e c k i arid S t i l e s , ( 1 9 6 7 ) and Ruddock (1972) have suggested l e s s w e i g h t be p l a c e d on e s t i m a t e s o f m a c u l a r pigment d e n s i t y made by use o f t h e e n t o p t i c phenomena. INCREASES IN THE MACULAR PIGMENT DUE TO AGEING S t i l e s and B u r c h (1959) i n d i c a t e t h a t t h e m a c u l a r pigment d e n s i t y i n c r e a s e s a s a f u n c t i o n o f t h e age o f t h e o b s e r v e r . By n o t i n g o b s e r v e r v a r i a t i o n s i n t h e r e s u l t s o f t h e i r  10°  c o l o r m a t c h i n g 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 n o t a l l o f t h e v a r i a n c e c o u l d be a c c o u n t e d  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 t h e m a c u l a r pigment might i n c r e a s e w i t h age 23.  A c c o r d i n g t o my d a t a on s o l v e n t s f o r x a n t h o p h y l l , c h l o r o f o r m p r o d u c e s a peak a t a p p r o x i m a t e l y 455 nra w h i l e o t h e r s o l v e n t s (such as e t h a n o l 98$ and a c e t o n e ) s h i f t t h i s peak a s much a s 10 nm.  -21-  Values of Lo^ &(frO?oA\oH<J- h Optical density <JT orie^W pi<jm»*  o o  Sao  9  -5QO  WAVELENGTH (nm)  F'lQUre 3f ^  E s t i m a t e o f t h e m a c u l a r pigment by N a y l o r and Stanworth (1954)  -22  also. Warburton (1953) came t o 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 ( e x p r e s s e d as a c o l o r t e m p e r a t u r e ) observers.  'B'  made by two groups  of  The f i r s t grout) aged 16-25 y e a r s matched t h e  s t i m u l u s c l o s e r t o i l l u m i n a n t * C T whereas the second  group  aged 56-65 y e a r s matched t h e s t i m u l u s n e a r 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 m a c u l a r pigment d e n s i t y .  Bone and S p a r r o c k ' s  increases (1971)  data  i n d i c a t e a v e r y s l i g h t upward t r e n d i n the o v e r 3 0 - u n d e r 22 age c o n t r a s t b u t do n o t i n c l u d e i n f o r m a t i o n w i t h r e s p e c t t h e s e two groups as t o t h e t o t a l age d i f f e r e n t i a l s  to  examined.  W r i g h t ( 1 9 4 6 ) , Weale (1963) and Ruddock (1965) have found no s i g n i f i c a n t increase age.  i n m a c u l a r pigment d e n s i t y w i t h  observer  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  m a t c h i n g d a t a c o r r e s p o n d c l o s e l y t o 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 t h e m a c u l a r  pigment cannot a c c o u n t f o r a l l o f t h e d i f f e r e n c e between t h e C . I . E , ^ 2 ° and 10° c o l o r m a t c h i n g f u n c t i o n s and some r e c e p t o r a l response d i f f e r e n c e s  therefore,  must be i n c l u d e d .  COLOR VISION TESTING The measurement 24.  o f t h e so c a l l e d n o r m a l / a b n o r m a l d i m e n -  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 t h e r w i s e known as t h e 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 .  -23-  s i o n s o f c o l o r v i s i o n have t a k e n t h r e e c h a r a c t e r i s t i c (a)  c o l o r m a t c h i n g (b) hue d i s c r i m i n a t i o n and (c)  forms:  color  c o n *f u s i•o n . 25 (a)  COLOR MATCHING There are two g e n e r a l methods o f c o l o r m a t c h i n g .  Firstly,  a moveable s e t o f samples can be matched t o a n o t h e r f i x e d which e x h i b i t a one-to-one correspondence.  set  (An example o f  t h i s t y p e o f method can be seen i n t h e ISCC C o l o r A p t i t u d e t e s t (1953)).  S e c o n d l y , 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 t h e y a re composed o f different  spectral characteristic.  use o f t h i s f a c t * .  METAMERIC MATCHING makes  Additive or subtractive mixtures of  light  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 m a t c h i n g f o r c o l o r  v i s i o n t e s t i n g can be a c h i e v e d by t h e use o f a s i m p l e a d d i t 26 i v e c o l o r i m e t e r known a s an anomaloscope, while subtractive metameric m a t c h i n g c.^n be a c h i e v e d by t h e 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 t h e t i n t o m e t e r . The most common meta25.  The l a s t f o r m can be seen as an a t t e m p t t o s e p a r a t e t h e human p o p u l a t i o n i n t o two f i r s t l y , two g r o u p s ; 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 c o n f u s i o n s w h i c h 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 i n s t r u m e n t i s used i n t h e p r e s e n t 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 later.  27.  The L o v i b o n d S c h o f i e l d T i n t o m e t e r 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 w h i c h 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 ation of c o l o r . I t requires a f a i r l y s p e c i a l i z e d observer and p r o p e r methodology t o m a i n t a i n c o n s i s t e n c y .  -24-  m e r i c i n use f o r d i a g n o s i s o f 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 t h e a d d i t i v e m i x t u r e o f r e d and green  l i g h t one can produce a y e l l o w l i g h t w h i c h can be matched t o a n o t h e r "pure" y e l l o w l i g h t .  I f t h e two " y e l l o w s " match  t o a p a r t i c u l a r o b s e r v e r , t h e two a r e d e f i n e d as a metameric pair.  Now i n t h e n o r m a l p o p u l a t i o n t h e r e i s a range o f  r a t i o s ( i . e . amount o f r e d t o amount o f green) t h a t w i l l produce a y e l l o w w h i c h i s a c c e p t e d as m a t c h i n g t h e p u r e yellow.  Extreme i n c r e a s e s o r extreme d e c r e a s e s  in this  ratio  a r e s t i m u l u s p a r a m e t e r s w h i c h 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  color d e f e c t i v e observers.  As w e l l a s t h e  R a y l e i g h e q u a t i o n , o t h e r metameric matches a r e p r e s e n t l y employed i n r e s e a r c h , n o t a b l y t h e y e l l o w - b l u e e q u a t i o n and the blue-green  o r violet/blue-green equation.  Lakowski  (1971)  p o i n t s o u t t h a t any number o f o t h e r e q u a t i o n s c o u l d be u s e d . P r e s u m a b l y , t h e R a y l e i g h , y e l l o w - b l u e and b l u e - g r e e n  equations  are u s e f u l i n determining the normality/abnormality o f o b s e r v e r s who f a l l i n t o t h e h i s t o r i c a l l y d e f i n e d c o l o r d e f e c t classifications. (b)  COLOR DISCRIMINATION As opposed t o m a t c h i n g 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 t h e o b s e r v e r t o n o t e t h e emphasis o f d i f f e r e n c e s and 28.  Named a f t e r L o r d R a y l e i g h n o t e d E n g l i s h p h y s i c i s t i n t h e 19th Century..  -25-  not  just  similarities.  present. is  Wavelength  generally  ators the  observer.  is  usually  in  color  out with  I n much  i s required  interpreted  parameters  100-hue  The t e s t  containing into  a  separate  four boxes  There  the so-called  In  each box the caps  order the  caps  score this  ity  received, i s that  A  an e x p e r i e n c e d  of colors  t h e box score  =  part  have  published  as a color  and t h e degree  t h e ends  i n the box. (perfect)  The degree  figure  each  caps.  represent  order  to which  increases  procedure  cap can be graphed  The r e s u l t a n t  population  21  i n a CORRECT  correct  caps,  i s divided  contained  the  of  in a  can be g l a n c e d  at  o f normality/abnormal-  on i t s c h a r a c t e r i s t i c s c a n be q u i c k l y  authors  differences  plotted  about  o f the scoring  o f each  tester  The t e s t  0,  out o f this  score  however,  o f determining  containing  can be a r r a n g e d  configuration.  noticeable  i n each box which  useful  and  The data  f o rcolor  color.  each  continium  case  of just  threshold  Munsell  are displaced  test  polar by  i n which  presented.  i s c o m p o s e d o f 85 m o v e a b l e  caps  of  a comparison f o r  i s the use o f the Farnsworth-Munsell  or series  a r e two f i x e d  raonochrora-  similarities  A n o t h e r method  discrimination  color  as t h e anomaloscope i s  t o note  i n terms  o f wavelength.  spectral  the use o f several  i n t h e two s t i m u l i  test.  a r e emoloyed a t  involving  t h e same w a y  o r as a difference  function  methods  monochromators which present  used, the observer differences  basic  discrimination  carried  o r double  Two  determined.  and age norms  Several  f o r t h e 100-  -26t e s t and t h e s e a r e summarized by L a k o w s k i 1969  hue (c)  (b)  COLOR CON FUSION C o l o r c o n f u s i o n t e s t s can be used t o determine t h e  e x t e n t t o w h i c h an o b s e r v e r d e v i a t e s from n o r m a l c o l o r vision.  L a k o w s k i I969 (a) d i f f e r e n t i a t e s between  discrimination  color  and c o l o r c o n f u s i o n t h u s :  Normal o b s e r v e r s a r e c a p a b l e o f d i s t i n g u i s h i n g a l a r g e number o f c o l o r s whereas a c c o r d i n g t o some a u t h o r i t i e s the d i c h r o m a t ' s c o l o r w o r l d i s l i m i t e d t o l e s s t h a n 30 d i s c r i m i n i b l e hues. These s u b j e c t s c o n f u s e c o l o r s t h a t a r e e a s i l y r e c o g n i z e a b l e by t h e man i n t h e s t r e e t . I f someone m i s t a k e s one p r i m a r y c o l o r f o r a n o t h e r we use t h e term c o l o r c o n f u s i o n t o i n d i c a t e t h e g r o s s n a t u r e o f t h e m i s t a k e , but f o r t h o s e whose l o s s e s a r e l e s s extreme we t a l k about p o o r 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 t h e r e a r e wide v a r i a t i o n s i n t h i s ability. ? 2  Generally,  there are a set o f t e s t s which only dichotomize  t h o s e who confuse c o l o r s from t h o s e who do n o t . These a r e c a l l e d Pseudoisochromatic p l a t e s  (PIC p l a t e s )  consist of a figure-ground pattern are  and  i n a set o f c o l o r s which  c o n f u s e d by a c e r t a i n c l a s s i f i c a t i o n o f c o l o r  observers.  generally  defective  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 b a c k g r o u n d .  The e n t i r e p a t t e r n i s  composed o f c i r c l e s o f v a r i o u s s i z e s - t h e f i g u r e b e i n g composed o f one p a r t i c u l a r c o l o r e d that  o r group o f c o l o u r e d  c o u l d be c o n f u s e d w i t h t h e b a c k g r o u n d .  Normal  see t h e f i g u r e - g r o u n d r e l a t i o n s h i p whereas d e f e c t i v e s  circles subjects do n o t .  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 t h e s e t e s t s as p o i n t e d o u t by 29.  L a k o w s k i 1969  (a) pg  186.  -27L a k o w s k i (1964) t h a t t h e f i g u r e on the b a s i s o f b r i g h t n e s s These t e s t s are  generally  and t e s t i n g o f g r o s s  can sometimes be  discerned  cues and not j u s t c o l o r c u e s . considered useful only for  screening  defects.  A c o n f u s i o n t e s t based on t h e 100 hue t e s t i d e a was developed by F a r n s w o r t h (1943) c a l l e d t h e F a r n s w o r t h Dichotbraous T e s t o r P a n e l D-15 i s u s e f u l f o r g r o s s measures l i k e t h e PIC p l a t e s . A g a i n as i n the 100hue 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 i m a t e 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 t h e a f o r e m e n t i o n e d  t e s t s i n (a)  and  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 .  In  general,  (b)  because o f the r e l a t i v e l y s h o r t p e r i o d o f t i m e  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 , t h e s c o p e , and the PIC t e s t s a r e most o f t e n  anoraolo-  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 L a k o w s k i (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 a g e i n g 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 1 9 4 0 ' s . investigated  Tiffin  and Kuhn (1942)  t h e 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 w o r k e r s 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 between the ages o f 25 and 55 y e a r s .  colors  Smith (1943) however  n o t e d no s t r o n g t r e n d t o 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 o v e r 65. findings  As a response t o T i f f i n and K u h n ' 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  (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 t o a g e i n g b e -  tween 20 and 59 y e a r s - n e i t h e r d i d Chapanis Chapanis r e p o r t e d s e v e r a l  Paterson  (1950).  e a r l i e r studies pointing to  However, the  - 2 8 -  tendency o f o l d e r s u b j e c t s t o have g r e a t e r d i f f i c u l t y b l u e - g r e e n , 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 .  with  These e a r l i e r  a u t h o r s s t a t e d t h a t t h e y e l l o w i n g o f the l e n s w i t h age may p l a y a r o l e i n the d i s c r i m i n a t i o n o f the blue-end o f the spectrum by a c t i n g l i k e a m i n u s - b l u e a b s o r p t i o n ( G i l b e r t , (1957))•  filter  L a k o w s k i (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 t o r e d , y e l l o w and green a s w e l l a s b l u e ( G i l b e r t , 1 9 5 7 ) .  S t i l e s and B u r c h  (1959) n o t e d changes i n c o l o r m a t c h i n g w i t h age and a l o n g w i t h Warburton  (1953) a t t r i b u t e d p a r t o f t h e s e changes w i t h  changes i n t h e m a c u l a r pigment d e n s i t y a s w e l l a s t h e l e n s transmission  characteristics,  W r i g h t (1952) a l s o p o i n t s o u t  t h a t e l d e r l y o b s e r v e r s may e x h i b i t some o f t h e 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 a c c o u n t 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. S e v e r a l i n v e s t i g a t o r s have attempted t o r e p r o d u c e t h e 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 various ageing studies.  I n general, the experimental  v a r i a b l e s i n c l u d e attempts a t e s t i m a t i n g the o c u l a r 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 and m a c u l a r pigment d e n s i t y  30.  W r i g h t (1952) p g 510  required  -29-  t o 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 n o t e d i n ageing observers. of increases  L a k o w s k i (1962b) i n v e s t i g a t e d t h e  effects  i n the s e l e c t i v e a b s o r p t i o n o f b o t h l e n s and  m a c u l a r pigments on younger s u b j e c t s , the d a t a o f o l d e r s u b j e c t s .  and made comparisons  H i s d e s i g n e n t a i l e d the p l a c e -  ment o f m i n u s - b l u e c o l o r f i l t e r s o v e r t h e o b s e r v e r ' s and t e s t i n g t h e i r m a t c h i n g ranges on the t h r e e equations  (mentioned i n an e a r l i e r s e c t i o n ) .  eyes  anomaloscope Figure 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 t h e I l f o r d f i l t e r s r e p o r t e d by L a k o w s k i ( 1 9 6 2 ) . supposed t o compensate  to  Although the f i l t e r s  as  are  f o r t h e d i f f e r e n c e between t h e 21  y e a r o l d s u b j e c t s and the v a l u e 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 approximations are a l l o v e r - e s t i m a t e d by t h e I l f o r d  series f i l t e r s .  Even s o ,  L a k o w s k i r e p o r t s t h a t o n l y t h e two most dense I l f o r d filters  (106 and 1 0 9 ) produced anomaloscope m a t c h i n g  r e s p o n s e s i n t h e 21 y e a r o l d s u b j e c t s w h i c h were comparable t o t h e b e s t s c o r e s on t h e same measure o f t h e l a s t two age groups ( 5 6 - 6 5 and 66-h ) .  He f u r t h e r p o i n t s out t h a t  it  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 t h e e s t i m a t e d v a l u e s o f S a i d and W e a l e s ' s olders subject's lens.  (1959)  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 t h e e x p e r i m e n t a l l e n s e s o f young n o r m a l o b s e r v e r s  i n order to  account f o r t h e changes found i n aged s u b j e c t s .  Because t h e  a d d i t i on o f t h e m a c u l a r pigment d e n s i t y ( e s t i m a t e d by Wald  -30-  Ilford filters  400  450  500  WAVELENGTH (nm)  FiCjUFG J  4  Experimental simulation f i l t e r s used by Lakowski (1962)  -31-  f o r a 60 y e a r o b s e r v e r t o be 1 o p t i c a l d e n s i t y a t 460 nm) would i n c r e a s e t h e c u r v e c h a r a c t e r i s t i c s t o be c l o s e r to t h e d e n s e s t I l f o r d f i l t e r s , L a k o w s k i c o n c l u d e d t h a t not  just  t h e l e n s medium o r t h e m a c u l a r pigment but at l e a s t b o t h were needed t o 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 t h r o u g h the o o t i c a l media and m a c u l a : I n t h e n o r m a l 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 p e o p l e 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 t h e r e a l s o seems t o be an i n c r e a s e i n the i n c i d e n c e o f p e o p l e 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 g e n e r a 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 t h e 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 t h e 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 increase i n macular pigmenta t i o n t h a t i s so o f t e n p o s t u l a t e d . Some m a t c h i n g p a t t e r n s however, a r e 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 t h a t l e n s could ' q u i t e s a f e l y '  changes  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 t h e v i o l e t end o f t h e 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 a c c o u n t f o r t h e l e n s as b e i n g t h e ONLY f a c t o r i n v o l v e d i n t h e o b s e r v e d d e t e r i o r a t i o n due t o a g e . ^ 2 Verriest  (1963 ( a ) )  made use o f a group o f  filters  r e s e m b l i n g v a l u e s w h i c h i n c r e a s e i n t r a n s m i s s i o n from 31.  L a k o w s k i (1962) pg 8 4 .  32.  i b i d , pg 8 5 .  -32-  a o p r o x i m a t e l y 5 t i m e s t h e v a l u e o f the o c u l a r media a s c a l c u l a t e d by L u d v i g h and McCarthy (1938).-^ an extreme minus-blue wavelengths  f i l t e r which absorbed  below 500 nm.  shown i n F i g u r e 5.  He a l s o used virtually a l l  The f i l t e r c h a r a c t e r i s t i c s a r e  S u b j e c t s were examined on a b a t t e r y o f  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, p a n e l D-15 and ( R a y l e i g h 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 e q u a t i o n s  w i t h the N a g e l 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 n o t attempt t o account f o r l e a r n i n g e f f e c t s by c o u n t e r b a l a n c i n g t h e o r d e r o f p r e s -  35  entation  and t h e sequence o f f i l t e r s  worn and t h e r e f o r e  t h e r e s u l t s r e p o r t e d may n o t t r u l y r e p r e s e n t t h e e f f e c t s o f the e x p e r i m e n t a l f i l t e r s  reported.  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 e r a l l y weighted  a r e gen-  towards t h e b l u e f i l t e r o f t h e p a i r .  f i n d i n g i s understandable  i n terms o f t h e 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 , F u r t h e r , t h e matching  This  i . e . , t h e y absorb b l u e  light.  ranges a r e e n l a r g e d , a c c o r d i n g t o  V e r r i e s t , e s p e c i a l l y i n t h e T r e n d e l b e r g 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 t h e K f i l t e r no match was  possible.  33.  As r e p o r t e d by Judd, P l a z a and F a r n s w o r t h  34.  See s e c t i o n on t h e anomaloscope.  35.  A s p i n a l l (1968)  (1950).  -33-  Verriest filters.  (1963)  Experimental  J  -34-  Mean  o o I X c  < H(D U <+ n> <+  p a r t i a l error score  o  c n  a> o  S3 o  TJ 3 C  3  d 3  c/> o o •1 a>  O c so m  o  CD  CP  o <-tco  L!  -•  I-  ; i !  3  M)l  < u  f  {  ?  5  S J  -35In a d d i t i o n , the experimental  f i l t e r s produced  detri-  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 t h e 100 hue t e s t , m a i n l y i n ' t h e r e g i o n s o f t h e b l u e - g r e e n 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 o n l y o b s e r v e d  when t h e extreme minus-blue f i l t e r K " was used w i t h t h e n  P a n e l D-15 t e s t o r AO H-R-R P l a t e s , o r u n d e r . s e v e r e l y reduced i l l u m i n a t i o n .  I n a r e l a t e d study, V e r r i e s t e t a l .  (1963 b) r e p o r t t h a t normal s u b j e c t s become w h o l l y  tritan-  o p i c a t 0 . 2 1 6 L x . The r e s u l t s o f reduced i l l u m i n a t i o n upon 100 hue s c o r e s f o r 2 5 n o r m a l s u b j e c t s aged 20-24 under illurainant C T  T  are presented  s i z e s h o u l d be taken 37 (1961)  i n F i g u r e 6.  Effects of pupil  i n t o c o n s i d e r a t i o n a c c o r d i n g t o Weale  who p o s t u l a t e s t h a t 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  l e n s i n c r e a s e s a t t h e c e n t r e o f t h e l e n s due t o i n c r e a s e s i n the o p t i c a l p a t h 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 o f p o s s i b l e importance i n a c c o u n t i n g  for  the ageing p o p u l a t i o n parameters o f c o l o r v i s i o n . A s o i n a l l (I96&) i n v e s t i g a t e d t h e e f f e c t s o f s i m u l a t e d m a c u l a r changes on t h e 100 hue t e s t . of the experimental  As w i t h V e r r i e s t , one  f i l t e r s used by t h e a u t h o r was extreme.  F i g u r e 7 shows t h e s p e c t r a l d e n s i t i e s o f t h e m a c u l a r s i m u l 3 6 . V e r r i e s t p o i n t s o u t t h a t o f t h e two r e g i o n s , t h e b l u e / green r e g i o n i s e f f e c t e d more than t h e r e d (1963) p g . l 8 £ 37.  ibid.  (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 n o t e the x a n t h o p h y l l 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 t o be i n a c c o r d a n c e w i t h t h e r e p o r t e d l e v e l s o f V e r r i e s t * s C a n d E f i l t e r s and u s i n g t h r e e d e n s i t i e s o f 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 . the experimental  in  With  f i l t e r s on young n o r m a l eyes A s p i n a l l found  a s h i f t i n t h e e x p e c t e d e r r o r a x i s , due  to ageing  o b s e r v e r s , about f i v e o r so caps c l o c k w i s e .  of  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  n o t as l a r g e at the r e d end as r e p o r t e d by A s p i n a l l . s m a l l e r r o r 'bulge'  A  i n c r e a s e d 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 a t cap 25 as w e l l .  Test e x p e r i e n c e  i s purported  to play  a r o l e i n t h e r e s u l t s and A s o i n a l l a n a l y z e d t h e d i f f e r e n c e s between e x p e r i e n c e d that experienced  and  inexperienced  subjects.  He  found  s u b j e c t s 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 i n e x p e r i e n c e d  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 a r e the same, t h e d i f f e r e n t i a l of the experimental  f i l t e r s must be due  effect  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 o f the f i l t e r s .  Further  a n a l y s i s o f the d a t a l e d t h e a u t h o r t o r e p o r t  significant  d i f f e r e n c e s f o r b o t h l u m i n o s i t y and  f i l t e r absorption  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 t o 100 hue 38.  performance than r e d u c t i o n s i n l u m i n o s i t y " .  The  As has been n o t e d e a r l i e r , the peak a b s o r p t i o n may v a r y as a f u n c t i o n o f the s o l v e n t b u t , i t a p p e a r s from the d a t a p r e s e n t e d by the a u t h o r t h a t c h l o r o f o r m was u s e d .  -37-  WAVELENGTH (nm)  FlQUre ^  7  A s p i n a l l ' s (1968) E x p e r i m e n t a l s i m u l a t e d M a c u l a r Pigment f i l t e r s (Xanthophyll i n Chloroform) •  -38-  c o n c l u s i o n s t a t e d here i s understandable  i n view o f t h e  extreme c o n c e n t r a t i o n s used i n the e x p e r i m e n t a l  filters*  SUMMARY AftD PROPOSAL I t can be seen from the p r e c e d i n g review t h a t (a) there i s evidence f o r t h e e x i s t e n c e o f both macular and l e n t i c u l a r pigmentation  i n the human eye and (b) that  pigments a f f e c t performance it  on c o l o r v i s i o n t e s t s *  these  Further,  can be p o s t u l a t e d from a r e a s o n a b l y l a r g e amount o f  comparative  and e x p e r i m e n t a l evidence t h a t one o r both o f  the pigments i n c r e a s e i n v i v o w i t h age and, a l o n g w i t h reductions i n r e t i n a l illumination  ( e i t h e r as a r e s u l t o f  these i n c r e a s e s o r due t o p u p i l l a r y changes e t c . ) c o n t r i b u t e to the observed d e t e r i o r a t i o n o f c o l o r v i s i o n w i t h a g e i n g . E x p e r i m e n t a l approximations o f these two pigments have n o t been as a c c u r a t e as  p o s s i b l e i n view o f t h e p s y c h o p h y s i c a l  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 i n t e r p r e t a t i o n o f r e s u l t s i n terms o f t h e r e g e n e r a l i z a b i l i t y t o human ageing p r o c e s s e s , a h i g h e r degree  o f accuracy might be d e s i r a b l e .  -39-  Wald's m a c u l a r pigment and Ilford filters Lakowski (1962)  |.0  o.S  >  0.1  CO  CA  LU Q  O.I  45o  400  < O  550  5ao  J  U  lo  Wald's 'macular pigment' e s t i m of Said Weale's l e n s stimates f o r k  O O.io  40o  ^5Q  -5bO  WAVELENGTH (nm) Figure 8  uo  EXPERIMENT I . The p r e s e n t e x p e r i m e n t was based upon the L a k o w s k i (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  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 e x p e r i m e n t a l aims p r e s e n t e d above.  covered e a r l i e r , and study t h e i r e f f e c t s  to  characteristics  based upon t h e r e n o r t s o f v a r i o u s  of several color vision  the  The a u t h o r a t t e m p t e d  s i m u l a t e t h e l e n s and m a c u l a r a b s o r p t i o n separately,  although  authors  upon performance  tests.  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 a p p r o x i m a t i o n f i l t e r s were based upon t h e c h a r a c t e r i s t i c age-dependant Weale ( 1 9 5 9 ) .  c u r v e s as r e p o r t e d by S a i d and  Compensation f i l t e r s were c o n s t r u c t e d u s i n g  t h e 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 . 39 cells,  Quartz  d e s i g n e d t o 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 designed to approximate the pigmentation.  The method o f d e r i v i n g t h e d e n s i t i e s o f  s o l u t i o n i s as f o l l o w s :  Firstly,  lens  this  two s t o c k s o l u t i o n s o f  extreme d e n s i t y ( 1 . 5 0 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 c o m m e r c i a l l y a v a i l a b l e w a t e r - s o l u b l e P o l a r Y e l l o w 2G c o n c . Q N e o l a n Grey RC 200$ ^  dyes:  5.0mm  39.  Path length of l i q u i d  LO,  My t h a n k s t o D r . R . S . S i n c l a i r , Department o f C h e m i s t r y , P a i s l e y College of Technology, P a i s l e y , S c o t l a n d , f o r suggesting these dyes.  41  b o t h 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 t o a c h i e v e t h e i n c r e a s e i n b l u e - a b s o r p t i o n w h i l e Neolan Grey was used t o . r e d u c e spectrum.  the  transmission across the  Because o f t h e r e l a t i v e l y  s m a l l amounts o f  s o l u t i o n r e q u i r e d and t h e extreme c o n c e n t r a t i o n o f t h e dyes the p r e c i s e measurement o f t h e c o n c e n t r a t i o n s BY WEIGHT was impractical.  Therefore  c o n c e n t r a t i o n s were a p p r o x i m a t e d by  d i l u t i o n w i t h t h e s o l v e n t ( i n t h i s case w a t e r ) . tion ing  characteristics  The a b s o r p -  were measured on a UNICAM SP 800 r e c o r d -  spectrophotometer.^  As t h e r e a l t o t a l o p t i c a l  measurements s h o u l d i n c l u d e t h e f a c t o r s o f t h e c e l l ,  density solvent  and d y e , t h e second beam o f t h e s p e c t r o p h o t o m e t e r was used 42  w i t h no b l a n k i n p l a c e .  Thus, measurements o f t h e e x p e r i -  m e n t a l c e l l s gave e s t i m a t e s o f t h e t o t a l o p t i c a l t h e f i l t e r as a whole.  density of  Some c o n c e n t r a t i o n s p r o v e d t o be  c l o u d y due t o i n h o m o g e n e t i e s i n t h e dye. F i l t e r i n g w o u l d not remove t h i s and so t h e 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 m i n u t e s a t 9.000 g s t o remove t h e s u s p e n s i o n . f  concentrations o f Approximating sate f o r the estimated  F i l t e r s designed  The f o u r  t o compen-  amounts o f l e n s pigment a l r e a d y  41.  T h i s use o f t h i s i n s t r u m e n t was p r o v i d e d c o u r t e s y 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 m e a s u r i n g absorbance o f c h e m i c a l s i n s o l u t i o n , t h e c h a r a c t e r i s t i c s o f t h e c e l l and t h e s o l v e n t used a r e b a l a n c e d o u t i n a second l i g h t p a t h i n t h e i n s t r u m e n t and n u l l i f i e d i n t h e r e c o r d i n g .  42.  e x t a n t i n t h e 2 1 - y e a r - o l d eye a r e shown i n f i g u r e 1 . 9 . The M a c u l a r 'Pigment' S i m u l a t i o n Compensation f i l t e r s  Filters  f o r t h e s o - c a l l e d m a c u l a r pigment  were c o n s t r u c t e d on t h e b a s i s o f t h e e s t i m a t e d v a l u e s o f Bone and S p a r r o c k  (1971).  Although  i t can r e a d i l y be seen  t h a t e s t i m a t e s f o r t h e m a c u l a r pigment a r e q u i t e v a r i a b l e , if i tfirstly  can be assumed t h a t t h e r e i s a m a c u l a r p i g -  ment, t h e r e seems t o be e v i d e n c e f o r an average d e n s i t y o f about 0 . 5 - 0 . 6 O.D. Bone and S p a r r o c k ' s  estimation 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 v a l u e was d e c i d e d upon i n v i e w o f i t s c o n s i s t e n c y w i t h o t h e r t i o n s and t h e r e l a t i v e l y l a r g e sample.  estima-  F o u r d e n s i t i e s were  made based on t h e assumption t h a t t h e s u b 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 t h e mean amount o f p i g m e n t . ^  These f i l t e r s  w o u l d , then add t o t h e e x i s t i n g amount o f pigment ( a t 455nm) by 0 . 2 , 0 . 4 , 0 . 6 , and 0 . 8 O.D.  T h i s would make t h e maximum  m a c u l a r pigment ( e x p e r i m e n t a l 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 t o 1 . 3 3 O.D.  d i s s o l v e d i n Chloroform  Lutein Xanthophyll  was  t o y i e l d t h e c h a r a c t e r i s t i c two-  peaked curve a t f o u r c o n c e n t r a t i o n s . 43.  ( C ^ Q H ^ O H ^ )  Due t o t h e n a t u r e o f  T h i s a s s u m p t i o n was made f o r b o t h t h e l e n s and m a c u l a r pigment. A l t h o u g h i t i s t o be r e c o g n i z e d t h a t t h e l e n s s i m u l a t i o n f i l t e r s a r e f o r 2 1 year o l d e y e s , t h e c u r v e s in f i g u r e 1 point to the r e l a t i v e l y small difference in the f i r s t 1 0 years.  43.  Soo  4oo  WAVELENGTH (nm)  Figure 9  Absorption C h a r a c t e r i s t i c s of t h e S i m u l a t e d Lens F i l t e r s ( A p p r o x i m a t i o n s o f Ages as r e p o r t e d by S a i d and Weale (1959)).  UK.  t h e crude X a n t h o p h y l l used i t was i m p o s s i b l e t o o b t a i n c o n s i s t e n t r e s u l t s by w e i g h t and t h e r e f o r e , a s w i t h t h e lens approximations, optical density.  t h e c o n c e n t r a t i o n s were d e t e r m i n e d by  A s t o c k s o l u t i o n o f 1 gram x a n t h o p h y l l  i n 100 m l . c h l o r o f o r m was made and f i l t e r e d 3 t i m e s t o remove i m p u r i t i e s .  D i l u t i o n o f the stock s o l u t i o n t o the  r e q u i r e d d e n s i t i e s was a c h i e v e d w i t h t h e u s e o f t h e s p e c t r o photometer mentioned p r e v i o u s l y .  The s p e c t r a l 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 f o r t h e 4 m a c u l a r f i l t e r s a r e shown i n f i g u r e 10. Q u a r t z c e l l s o f s i m i l a r n a t u r e t o t h e 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 t h e l i q u i d l e n g t h 2.5mm).^ the  (path  Due t o t h e e x t r e m e l y v o l a t i l e n a t u r e o f  s o l v e n t , t h e s o l u t i o n s were k e p t i n g l a s s - s t o p p e r e d  flasks.  As a p r e c a u t i o n a g a i n s t t h e p o s s i b i l i t y o f b o t h  ' l e n s ' and 'macular* f i l t e r  s o l u t i o n s being subjected  to  l i g h t - p r o d u c e d d e g r a d a t i o n , 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 t o spectrophotometric a n a l y s i s .  No o b s e r v a b l e  changes were found i n any o f t h e r e s u l t a n t  LL.  A l l s p e c t r o p h o t o m e t r i c measurements were made w i t h t h e experimental quartz c e l l s containing t h e i r respective liquids. The 2.5mm c e l l s were used f o r t h e m a c u l a r pigment s i m u l a t i o n (due t o t h e i r narrow o p e n i n g ) i n an attempt t o p r e v e n t e x c e s s i v e e v a p o r a t i o n d u r i n g testing. Stoppers o f neoprene rubber and s e v e r a l o t h e r s u b s t a n c e s were found t o p a r t i a l l y d i s s o l v e i n the c h l o r o f o r m , and t h e r e f o r e no s t o p p e r s were u s e d . The c e l l l e v e l s were m a i n t a i n e d as f u l l a s p o s s i b l e d u r i n g t h e e x p e r i m e n t by f i l l i n g w i t h a p i o e t t e .  45.  curves.  In t h e e x p e r i m e n t a l  s i t u a t i o n s mentioned i n t h e  f o l l o w i n g p a r t o f t h i s p a p e r , t h e s o l u t i o n s were to  t u n g s t e n - l i g h t o n l y , and t h e n o n l y when the  were e n t e r i n g o r l e a v i n g t h e room. were c o n c l u d e d ,  subjected  observers  A f t e r the e x p e r i m e n t s  the s o l u t i o n s were a g a i n measured and  changes were f o u n d .  no  F i g u r e 11 (a-d) g i v e s the s p e c t r a l  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 16 c o m b i n a t i o n s o f l e n s and m a c u l a r pigment s i m u l a t i n g f i l t e r s w h i c h w i l l be used (as w e l l as t h e f i l t e r s shown i n f i g u r e 9 and experimental  s i t u a t i o n s described herein.  the b r i g h t n e s s values  {%)  10) i n t h e  Table 3 g i v e s  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 o f the most dense  combinations.  U6  FiGlirG J  1Q  Absorption C h a r a c t e r i s t i c s of the Simulated macular pigment filters.  47.  WAVELENGTH  FlQUre  113  (nm)  Absorption C h a r a c t e r i s t i c s of Macular Simulation F i l t e r 'A* and E x p e r i m e n t a l lens values  48.  WAVELENGTH  FinUTQ 1  11b  (nm)  Absorption Characteri o f macular S i m u l a t i o n f i l t e r B ' and e x p e r i mental l e n s v a l u e s . !  Pinnro riLJUlL  11 r I IO  Absorption C h a r a c t e r i s t i c s of j ^ ^ a j . s i m u l a t i o n f i l t e r »C» and e x p e r i m e n t a l l e n s v a l u e .  51.  Table I I I B r i g h t n e s s V a l u e s o f t h e L e a s t and Most Dense E x p e r i m e n t a l Simulation F i l t e r s .  (LENS)  EXT  85  31  94  D  88  A  93  ( M a c u l a r pigment)  74.8  EXT + D Table I V  S i m u l a t i o n C o n d i t i o n s f o r Experiment  I  Macular Simulation  Len Simulation  (Space)  A  B  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  A  EXT  EXT  C  D  EXT+AEXT+B EXT+C EXT+D  OLens  i Macular  52 METHOD  Twelve o b s e r v e r s between 22 and 25 (mean age 2 3 . 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 t u d y and were randomly a s s i g n e d t o one o f f o u r experimental groups.  T e s t i n g took p l a c e a t t h e U n i v e r s i t y  o f B r i t i s h C o l u m b i a , P s y c h o l o g y Department between J u l y 5 t h and August 4 t h , 1972.  A l l s u b j e c t s were screened f o r g r o s s  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 A m e r i c a n O p t i c a l H-H-R P s e u d o i s o c h r o m a t i c p l a t e s ^ the C.W. DIXEY ACUITY CARD.  and f o r n e a r a c u i t y w i t h  O n l y I s h i h a r a o r AO H-R-R s c o r e s  o f zero were t r e a t e d as a c c e p t a b l e  f o r o b s e r v e r s as were  a c u i t y s c o r e s i n d i c a t i v e o f N5 v i s i o n . ing of subjects,  two o b s e r v e r s  and were r e p l a c e d .  Upon i n i t i a l  screen-  f a i l e d t o meet t h e s e c r i t e r i a  A l l t e s t i n g ' ^ premeasures  measures were done w i t h the r i g h t eye o n l y .  and e x p e r i m e n t a l I f the  wore c o r r e c t i v e l e n s e s f o r t h e n e a r a c u i t y t e s t , l e n s e s were worn t h r o u g h o u t t h e e x p e r i m e n t .  subject  these  After approxi-  m a t e l y ten m i n u t e s i n reduced i l l u m i n a t i o n , each o b s e r v e r was t e s t e d on t h e t h r e e e q u a t i o n s o f t h e P i c k f o r d - N i c h o l s o n anomaloscope and 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 d e t e r m i n e b a s e l i n e measures. possible  detrimental effects  As a precaution against produced by t h e l e n s e s a l o n e  on p e r f o r m a n c e , f o u r s u b j e c t s , 45.  to  one from each g r o u p , were  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 .  53.  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 a u a r t z c e l l  (water-filled)  2.  2.5mm q u a r t z c e l l  (chloroform-filled)  B o t h o f t h e s e g r o u p s showed no s i g n i f i c a n t o r s y s t e m a t i c 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 c o u n t e r b a l a n c e d 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 .  among t h e f o u r subA l l s u b j e c t s were  f i t t e d w i t h a s p e c t a c l e d e v i c e i n w h i c h t h e l e f t eye was o c c l u d e d and t h e r i g h t eye s i d e adapted t o h o l d two q u a r t z cells.  A l l s u b j e c t s were then t e s t e d under t h e s i x c o n d i -  t i o n s summarized i n T a b l e I V .  F o r t h e purpose o f a n a l y s i s ,  t h e c o n d i t i o n s where t h e r e i s o n l y one SIMULATIONS FILTER b e i n g u s e d , a r e c o n c e p t u a l i z e d a s u s i n g z e r o amounts o f the o t h e r f i l t e r d e n s i t y .  I n the experimental  situation,  s u b j e c t s a l w a y s had two c e l l s i n f r o n t o f t h e i r r i g h t eye and were n o t i n f o r m e d o f t h e d e n s i t i e s i n each c e l l .  Under  each o f t h e 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 E q u a t i o n Anomaloscope Y e l l o w - B l u e E q u a t i o n Anomaloscope - B l u e - G r e e n E q u a t i o n Anomaloscope Pseudoisochromatic  P l a t e s ( D v o r i n e and I s h i h a r a )  5U. The o r d e r o f p r e s e n t a t i o n o f t h e s e t e s t s and  the  m a c u l a r pigment s i m u l a t i o n f i l t e r s were c o u n t e r b a l a n c e d t h a t no two  so  s u b j e c t s under any o f t h e s i x c o n d i t i o n s  r e c e i v e d t h e f i l t e r s o r t h e sequence o f t e s t s under each of  them i n t h e same o r d e r .  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 t a k e n on each o f t h e twelve observers d u r i n g the experimental s e s s i o n .  The  100-hue and t h e P s e u d o i s o c h r o m a t i c p l a t e s were done under an a p p r o x i m a t i o n o f I l l u m i n a n t 'C  a t 100 e q u i v a l e n t l u x ,  w h i l e t h e t h r e e anomaloscope e q u a t i o n s were s e t i n a c c o r d ance w i t h L a k o w s k i ' s  (1971) measurements o f model I w h i c h  a r e summarized below: R-G T-B B-G The  E q u a t i o n 1.9 n i t s ( c a n d e l a s p e r square metre) E q u a t i o n 3.0 n i t s E q u a t i o n 2.2 n i t s  r e t i n a l i l l u m i n a t i o n f o r t h e anomaloscope a t t h e s e  l e v e l s i s between 30 and  50 T r o l a n d s (1 degree s u b t e n s e ) .  As the anomaloscope s e t t i n g s had t o be changed many t i m e s d u r i n g an e x p e r i m e n t a l s e s s i o n , the b r i g h t n e s s o f t h e matching  f i e l d was  determined  each t i m e w i t h t h e use o f an  S.E.I. E x p o s u r e Photometer. RESULTS The d a t a 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 t h r e e d i s c r e e t  55.  tests:  t h e Anomaloscope, t h e F a r n s w o r t h - M u n s e l l  t e s t and t h e P s e u d o i s o c h r o m a t i c  Plates.  100-hue  Each o f t h e t h r e e  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 a s s u m p t i o n must be made t h a t t h e r e a r e no i n t e r a c t i o n s between them.  significant  Because o f t h e s m a l l number o f  s u b j e c t s p e r g r o u p , d e s c r i p t i v e s t a t i s t i c s were employed, instead of i n f e r e n t i a l types.  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 p r e s e n t e d i n e i t h e r t a b u l a r or graphic  form.  56. The Anomaloscope The C o n t r o l C o n d i t i o n Table IV g i v e s t h e  raid-points  and  standard 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 o f t h e Anomaloscope f o r t h e NORMAL46 NO LENS and C o n t r o l groups*  The  red-green  equation  clearly  shows t h e l e a s t v a r i a n c e o f t h e t h r e e , w h i l e the o t h e r v a r y s l i g h t l y more.  two  The means o f each e q u a t i o n s M i d - P o i n t s  w i l l be used as t h e Standard M i d - P o i n t s f o r  comparison.  The Means and S t a n d a r d D e v i a t i o n s f o r s i n g l e c o n d i t i o n s are presented i n Table V .  The  latter  filter two  e q u a t i o n s , and e s p e c i a l l y t h e 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 t h e d e n s e r v a l u e s o f b o t h l e n s and pigment s i m u l a t i o n f i l t e r s .  macular  The M i d - P o i n t s and Ranges  (2x s t a n d a r d 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 and e n l a r g e d than t h e c o n t r o l s .  erratic  These do n o t apoear t o be  d i r e c t e d s h i f t s towards one anomaloscope f i l t e r o r t h e o t h e r , and, c o n t r a r y t o what would be expected from  the  p h y s i c a l p r o p e r t i e s o f 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 r o p o r t i o n s o f b l u e do n o t seem t o be i n d i c a t e d . 4£. The Mean and S t a n d a r d D e v i a t i o n a r e c a l c u l a t e d on t h e l o w e s t and h i g h e s t a c c e p t a b l e s c o r e s f o r each s u b j e c t T h e r e f o r e ; the Mean can be seen as t h e m i d p o i n t and t h e S t a n d a r d D e v i a t i o n can be seen as o n e - h a l f o f t h e Range.  57.  Table V Anomaloscope M i d - P o i n t s and Standard D e v i a t i o n s f o r the Control Conditions. GROUP I  Red-Green Equation  II  III  IV  Zero d e n s i t y cells control  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  Blue-Green Equation  X  38.4  43.5  40.8  41.5  41.1  SD  1.9  3.0  1.5  3.4  3.5  X SD  43.0 3.3  40.5 1.7  42.5 2.1  kh.8 2.9  42.1 0.5  Totals  ( f o r comparison Mean  Mid-Point  Red-green  40.6  Yellow-blue  41.1  Blue-Green  41.7  purposes)  58 Table  VI  Anomaloscope 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 S i n g l e F i l t e r Conditions. A  B  C  D  31  45  63  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  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  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  EXT  Red-Green Equation  Yellow-Blue Equation  Blue-Green Equation  59 Table V I I Anomaloscope M i d - P o i n t s .and Standard D e v i a t i o n s f o r T w o - f i l t e r Conditions. (a)  Red-Green E q u a t i o n Lens S i m u l a t i o n  A  B  Macular Simulation  C  D  31  45  63  EXT.  X  40.1  42.4  41.4  39.3  SD  1.8  2.0  1.1  0.7  X  40.2  41.3  41.0  40.0  SD  1.3  2.3  0.8  1.9  X  40.7  41.3  41.7  39.7  SD  1.4  2.1  1.3  1.5  X  40.7  41.0  41.2  39.8  SD  1.5  2.5  1.6  1.1  60. (b)  Yellow-Blue Equation  Lens S i m u l a t i o n  A  B  Macular Simulation  C  D  31  45  63  X  38.8  52.0  39.7  38.8  SD  10.2  15.1  12.6  20.4  X  39.2  45.7  41.0  31.3  SD  11.9  9.2  8.2  23.4  X  36.8  44.8  32.3  40.7  SD  17.6  11.8  24.2  6.7  X  38.3  30.7  35.2  31.2  SD  19.6  23.1  26.2  26.9  EXT  61. (c)  Blue-Green  Equation  Lens S i m u l a t i o n  A  B  Macular Simulation  C C  D  31  45  63  EXT  X  43.7  36.5  46.2  43.5  SD  9.7  8.9  8.3  4.9  1  46.8  47.0  44.3  40.2  SD  8.9  10.6  15.0  12.1  XX  44.7 44.7  45.7 45.7  35.2 35.2  SD  12.7  12.2  25.6  11.5  X  37.2  41.8  45.0  43.8  SD  24.0  16.0  19.0  45.8  6?.  Table V I p r e s e n t s t h e mean  raid-points  ranges f o r t h e T w o - F i l t e r Conditions«  and m a t c h i n g  The red-green  equa-  t i o n remains u n a f f e c t e d -by t h e e x p e r i m e n t a l  procedure.  E v e r y c o n d i t i o n remains c l o s e t o t h e c o n t r o l  mid-point  w i t h low matching  ranges.  The y e l l o w - b l u e e q u a t i o n shows  more e r r a t i c m i d - p o i n t s and i n c r e a s e d matching increasing f i l t e r density.  The most dense f o u r  ranges w i t h combinations  show m i d - p o i n t s h i f t s toward t h e y e l l o w s i d e o f t h e e q u a t i o n w i t h t h e matching units:  ranges encompassing up t o 54 Anomaloscope  almost t h r e e - q u a r t e r s o f t h e t o t a l p o s s i b l e range  of the instrument.  The b l u e - g r e e n e q u a t i o n shows m i d - p o i n t  s h i f t s toward t h e b l u e f i l t e r and m a t c h i n g ranges do n o t show a s l a r g e i n c r e a s e s as d i d t h e y e l l o w - b l u e e q u a t i o n . The F a r n s w o r t h - M u n s e l l  100-Hue T e s t  The means and s t a n d a r d d e v i a t i o n s o f each o f t h e f o u r boxes a r e p r e s e n t e d , f o r t h e s i n g l e c e l l c o n d i t i o n i n T a b l e VIII(a). I t a p p e a r s from t h e s e d a t a t h a t i n c r e a s e s i n m a c u l a r s i m u l a t i o n d e n s i t y tends t o a f f e c t Box t h r e e s c o r e s s t r o n g l y ; Box one and f o u r s c o r e s s l i g h t l y and Box two s c o r e s 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 t o a f f e c t Box  t h r e e s c o r e s s t r o n g l y , Box one and f o u r s c o r e s s l i g h t l y , and Box two s c o r e s h a r d l y a t a l l b u t n o t e , as a F u n c t i o n o f  63. Decreasing F i l t e r Density  and n o t 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 .  T h i s f i n d i n g can be a t t r i b u t e d  t o s u b j e c t b i a s as t h e 31 n d D groups were t h e same s u b j e c t s a  (see T a b l e I V ) . The t w o - c e l l c o n d i t i o n means and s t a n d a r d  deviation  are p r e s e n t e d i n T a b l e V I I I ( b ) . A g a i n , Box t h r e e 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 . m e n t a l groups show a g e n e r a l tendency t o h i g h e r  seems t o A l l experi-  scores  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 - l e n s s i m u l a t i o n 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 s c o r e s o f t h e o s e u d o i s o c h r o m a t i c p l a t e s showed no m i s t a k e s f o r any o f t h e s u b j e c t s u n d e r any f i l t e r c o n d i t i o n i n Experiment I .  with condi-  64. Table V I I I Means and S t a n d a r d D e v i a t i o n s f o r 100  hue t e s t (By  (a) S i n g l e C e l l C o n d i t i o n s  100  Box A  B  C  D  31  45  63  (only)  (only)  (only)  (only)  (only)  (only)  (only)  EXT(only)  1  Box)  Lux  Box 2  Box 3  Box 4  X  5.0  5.7  7.0  4.0  SD  4.5  4.0  4.2  3.3  X  5.3  4.0  6.7  5.3  SD  1.9  5.7  3.8  1.9  X  8.0  4.0  8.0  5.0  .SD  8.6  3.3  8.6  7.1  X  11.0  5.3  13.3  10.7  SD  5.1  3.7  5.0  6.8  X  7.7  8.0  13.7  10.3  SD  8.2  0.  8.2  4.9  X  10.0  3.0  11.3  4.0  SD  4.3  1.4  2.5  3.3  X  4.0  6.7  2.7  2.7  SD  5.7  5.0  1.9  1.9  X  5.3  4.0  5.3  2.7  SD  1.9  3.3  1.9  1.9  65.  (b)  Box A - 3 1  A - 4 5  A-63  A-EXT  B-31  B-45  B-63  B-EXT  1  Box  2  Box  3  Box  X  5.3  8 . 0  1 2 . 7  7.3  SD  5.0  11.3  9 . 6  7 . 7  X  4 . 0  6.3  8.3  5.3  SD  5.7  4 . 7  9 . 1  1.9  13.3  4.3  13.3  1 2 . 7  3.3  6.8  6.3  5.0  1 3 . 0  1 2 . 0  1.4  3 . 7  6 . 7  X  SD  5 . 0  X  5.7  SD  4 . 0  X  4 . 0  1 0 . 7  1 8 . 7  2 . 7  SD  5 . 7  1 0 . 0  1 3 . 6  1.9  X  6 . 7  6.3  1 5 . 7  5.3  SD  9 . 4  5.8  1 7 . 4  5 . 0  X  1 0 . 7  1 6 . 0  1 5 . 0  6.3  SD  1.9  7 . 3  9 . 2  4 . 0  X  4.7  5.3  9 . 7  1 1 . 0  SD  5.9  3.8  8 . 0  1 0 . 6  4  66.  C-31  C-45  C-63  C-EXT  D-31  D-45  D-63  D-EXT  Box 4  Box 1  Box 2  X  4.0  5.7  SD  3.3  5.4  X  6.7  12.3  25.3  9.0  SD  5.0  10.2  30.3  7.8  X  10.7  7.0  6.3  9.0  SD  5.0  5.4  6.3  6.7  X  7.7  4.3  14.3  9.7  SD  2.9  0.5  6.3  1.7  X  6.7  14.0  24.7  14.3  SD  3.8  7.3  X  14.7  12.3  SD  11.5  11.1  X  12.0  14.3  17.0  11.7  SD  5.7  4.5  4.2  7.6  X  8.3  7.3  20.7  15.7  SD  5.9  5.2  12.2  8.3  Box 3 15.0 6.1  4.1 19.3  8.1  9.7 11.0  9.0 16.3 6.0  67. EXPERIMENT  II  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 a d a p t a t i o n o f t h e of several authors.  finding  The s i m u l a t i o n f i l t e r s r e p o r t e d i n  E x p e r i m e n t I were used i n c o n c e r 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 i m u l a t e d m a c u l a r 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 e a c h i n g the eye would e f f e c t  color vision  test  s c o r e s from young s u b j e c t s i n a s y s t e m a t i c manner.  Verriest's  (1963) age norms f o r t h e 100-hue t e s t show g r a d u a l  increases  i n t h e b l U e - g r e e n ; and r e d r e g i o n s o f t h e t e s t w i t h  increases  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 . from t h e s e ,  He c o n c l u d e d  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  acquired blue-yellow 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 t o l i g h t so t h a t i t s s e n s o r y 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 d e f e c t o b s e r v e d 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 . If this e x p l a n a t i o n were t r u e , t h e 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 t h e 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 E x p e r i m e n t I , s i m u l a t e d changes o f b o t h l e n s and m a c u l a r a b s o r p t i o n do 47.  V e r r i e s t (1963) Pg 194-195  68.  n o t a d e q u a t e l y a c c o u n t f o r t h e a g e i n g changes o b s e r v e d by V e r r i e s t on t h e 100-hue p r o f i l e s b u t t o g e t h e r 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 t h e hue d i s c r i m i n a t i o n  tests  and s c r e e n i n g p l a t e s , t h e s e changes may be more d r a s t i c . The anomaloscope  m a t c h i n g d a t a f o r t h e y e l l o w - b l u e and b l u e -  green e q u a t i o n s shows some d e v i a t i o n from n o r m a l i t y a l o n g the  l i n e s o f an a g e i n g p o p u l a t i o n a s r e p o r t e d by L a k o w s k i  (1962).  Looking a t 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 , t h e q u e s t i o n s o f INCREASES i n t h e luminance of  t h e anomaloscope  might produce r e d u c t i o n s i n t h e v a r i a -  b i l i t y o f t h e ranges and  raid-points  found i n E x p e r i m e n t I .  M o d i f i c a t i o n s t o t h e P i c k f o r d - N i c h o l s o n Anomaloscope (Model I I I ) In for  order t o achieve the brightness l e v e l s required  t h e i n v e s t i g a t i o n s o f e x p e r i m e n t I I , m o d i f i c a t i o n s were  made t o t h e P i c k f o r d - N i c h o L s o n Anomaloscope used t h r o u g h o u t t h i s experiment.  These m o d i f i c a t i o n s were made i n t h e 1 g summer and e a r l y f a l l o f 1 9 7 1 by t h e a u t h o r . The P i c k f o r d - N i c h o l s o n Anomaloscope has been d e s c r i b e d  by L a k o w s k i ( 1 9 7 1 ) as a s i m p l e c o l o r i m e t e r .  I t i s basically  an a d d i t i v e c o l o r i m e t e r w h i c h c o n t a i n s a s o u r c e o f i l l u r a 2*3.  My t h a n k s t o K e i t h W a l d r o n , t e c h n i c i a n , P s y c h o l o g y Department, U.B.C. f o r h i s h e l p i n t h e m o d i f i c a t i o n s of t h i s i n s t r u m e n t .  69. i n a n t ' A 1 l i g h t , two s e t s o f f i l t e r h o l d e r s and  shutters  and two i n t e g r a t i n g chambers,  each o p e n i n g t o a s i n g l e  o f the same b i p a r t i t e  Three s e t s o f f i l t e r s a r e i n  field.  t h e P i c k f o r d - N i c h o l s o n Anomaloscope ically,  a l l classical  and w i t h them,  half .  theoret-  forms o f c o l o r v i s i o n d e f e c t can be  tested (Lakowski, 1971): Equation  Standard  Defect  Red - Green -  Yellow  P r o t a n - Deutan  Yellow - Blue -  Neutral  Tetartan  B l u e - Green -  Blue-Green  Tritan  The m o d i f i c a t i o n s  r e p o r t e d a l l o w the t e s t i n g  of  s u b j e c t s on the t h r e e e q u a t i o n s 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 t h o s e r e p o r t e d by L a k o w s k i 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 t e m p e r a t u r e  than S a a t  The i n s t r u m e n t was m o d i f i e d w i t h r e s p e c t t o i t s  2850°K.  source and  i t s l i g h t m i x i n g e n v i r o n m e n t s i n t h e f o l l o w i n g manner. o r i g i n a l s o u r c e and i t s  s o c k e t was removed from t h e  house assembly and t h e lamphouse  and i n t e g r a t i n g  The  lamp-  chambers  were sprayed w i t h a B a r i u m S u l n h i t e p a i n t m i x t u r e w h i c h was adapted from t h a t r e p o r t e d by M i d d e t o n and. Saunders ( 1 9 5 4 ) . The p a i n t was d i l u t e d i n a p p r o x i m a t e l y  1 n a r t acetone and  t h e l i q u i d was then a p p l i e d t o the s u r f a c e s o f the g r a t i n g chamber and the lamphouse.  The acetone  inte-  subsequently  70.  d r i e d l e a v i n g the barium sulphate  - carbonxymethyl-cell-  u l o s e m i x t u r e adhered t o the w a l l s .  Each o f t h e  integrating  chambers had one 9 0 ° c o r n e r made i n t o a 4 5 ° c o r n e r t o i n crease the b r i g h t n e s s apertures.  o f the l i g h t r e a c h i n g the  comparison  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 a s b e s t o s n l a t e w h i c h 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 w i t h the lamp.  R e f l e c t o r s were p l a c e d b e h i n d the s o u r c e i n  t h e a x i s o f each o f t h e two a p e r t u r e s . volt,  contact  150 w a t t q u a r t z - h a l o g e n  The source was a 24  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 a t p r e v i o u s l y mentioned l e v e l s  (Lakowski  1971)  the lamp was run a t a p p r o x i m a t e l y 13 v o l t s t o r e n d e r t h e 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 t h e 12 v o l t model found i n t h e i n s t r u m e n t as M o n i t o r i n g p l u g s were n l a c e d a t t h e r e a r o f t h e  well.  instrument  t o check t h e a p p l i e d v o l t a g e a t t h e s o c k e t o f t h e s o u r c e . o r d e r t o c o o l t h e source and s u r r o u n d i n g f i l t e r s e t c . ,  In  an  exhaust f a n assembly was f i t t e d t o the bottom o f t h e anomaloscope w h i c h f o r c e d a i r t h r o u g h the laraphouse and out the During 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 transformer used to c o n t r o l the v o l t a g e  t o the t r a n s f o r m e r ,  v o l t m e t e r was used t o m o n i t o r the s o u r c e . from f i g u r e 12 ( a ) ,  was  while a  As can be seen  the l i g h t l e a v i n g both apertures  is  top.  71.  SHUTTER  Figure 12a  SETTING  Aperture luminance i s a f u n c t i o n of shutter s e t t i n g .  72.  Illuminant v A ' 13 volts  2D  3o  $o  Cc  70 80  SHUTTER SETTING  P0  12b  A p e r t u r e luminance i s a function of shutter setting,  73. q u i t e u n i f o r m i n terras o f  brightness.  The anomaloscope f i l t e r s used i n t h i s e x p e r i m e n t those w i t h s p e c t r a l (1971) f o r model I .  characteristics  were  as r e p o r t e d by L a k o w s k i  Energy d i s t r i b u t i o n s f o r t h e s e  filters  a t the A p e r t u r e m o d i f i e d anomaloscope a r e p r e s e n t e d i n F i g u r e 13. METHOD The t w e l v e v o l u n t e e r s u b j e c t s r e p o r t e d i n E x p e r i m e n t  I  were dark adapted f o r 10 m i n u t e s and t h e n t e s t e d m o n o c u l a r l y ( r i g h t eye) under an a p p r o x i m a t i o n o f I l l u m i n a n t t o d e l i v e r 2 . 0 l u x o v e r a 30 x 10 cm a r e a .  T  C  masked  The o b s e r v e r s  wore two l i q u i d f i l t e r s i n f r o n t o f t h e r i g h t eye i n t h e manner r e p o r t e d i n E x p e r i m e n t I .  The f i l t e r s were p l a c e d i n  4 mutually i n c r e a s i n g p a i r s which represented  conditions  r a n g i n g from 31 y e a r s o l d l e n s p l u s low m a c u l a r pigment  to  extreme l e n s p l u s extreme m a c u l a r p i g m e n t .  (1963)  As V e r r i e s t  n o t e s , t h e n o r m a l s u b j e c t becomes ' w h o l l y t r i t a n o p i c ' when t h e i l l u m i n a n c e f a l l s below 0 . 2 l u x .  As a p r e c a u t i o n ,  all  s u b j e c t s were t e s t e d w i t h the P a n e l D-15 t e s t w i t h o u t t h e s i m u l a t i o n f i l t e r s a t 0 . 4 2 l u x t o d e t e r m i n e whether any 49.  These measurements were made on t h e same s o u r c e used i n t h i s e x p e r i m e n t , w h i c h was burned a p p r o x i m a t e l y 10$ 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 ) b e f o r e these measurements were t a k e n .  <Ko  40  *o MO  sa Sbo  *>  <u>,  <o&  WAVELENGTH (nm)  So  Loo  2.6  6>o go  Too  Figure 13 Spectral characteristics of Anomaloscope f i l t e r s (Model at aperture.  I)  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 . d e n s i t y f i l t e r s (combined  Y%-21)  reduction in i l l u m i n a t i o n .  Two n e u t r a l  were used t o a c h i e v e  A l t h o u g h some o b s e r v e r s  the  made  t r i t a n o p i c c o n f u s i o n s , t h e 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  sented i n f i g u r e 1 4 .  pre-  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 t h e n p l a c e d i n t h e 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 - 1 5 ,  and D v o r i n e and AO H-R-R p s e u d o i s o c h r o m a t i c p l a t e s . j e c t s were r e q u i r e d t o h o l d t h e n e u t r a l d e n s i t y throughout the experiment. filters  filter  The maximum d e n s i t y p a i r o f  (ext l e n s + D macular) represent  a reduction of  27% (Y# ~ 7 3 ) , t h e r e f o r e , t h e l o w e s t l e v e l o f  illumination  a c h i e v e d u n d e r t h e reduced i l l u m i n a t i o n and f i l t e r i s 0.31 e q u i v a l e n t l u x . respective  Sub-  conditions  The same o b s e r v e r s w i t h t h e i r  l e n s and m a c u l a r s i m u l a t i n g f i l t e r s  (without  t h e N e u t r a l D e n s i t y f i l t e r s ) were a l s o t e s t e d on t h e  three  anomaloscope  each  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 f o r  e q u a t i o n as r e p o r t e d i n E x p e r i m e n t I .  A l l above mentioned  t e s t s were p r e s e n t e d i n a c o u n t e r b a l a n c e d o r d e r t o e l i m i n a t e 50. S u b j e c t s were r e q u i r e d t o h o l d t h e 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 of t h e i r r i g h t eye.  76.  77.  78. learning effectSo  A s i n E x p e r i m e n t I,  r e c e i v e d any o f t h e t e s t s  no two s u b j e c t s  i n t h e same o r d e r .  RESULTS: The A n o m a l o s c o p e T a b l e IX shows t h e m i d - p o i n t s f o r the three  and s t a n d a r d  deviations  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  i n Experiment I.  There i s a d i s t i n c t  reported  decrease i n the  ranges o f b o t h the y e l l o w - b l u e and b l u e - g r e e n  equations  under t h e extreme c o n d i t i o n s a n d , i n a d d i t i o n ,  the mid-  p o i n t s a p p e a r , t o be s h i f t e d v a l u e s o f each p a i r . the mid-points  slightly  towards the blue  As i n the p r e v i o u s l y noted  filter  findings,  and ranges f o r t h e r e d - g r e e n e q u a t i o n  remain  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 a n d 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  performed under very low i l l u m i n a -  t i o n , with the experimental f i l t e r s . densities affect  The i n c r e a s i n g  B o x one a n d B o x t h r e e  a s c a n b e s e e n b y F i g u r e 15  the most,  there are high e r r o r  t h e b e g i n n i n g and end o f e v e r y b o x i n t h e h i g h conditions.  filter  although scores at  density  79.  3U.5  Figure 15 b  81.  > 0.31 Ix  Figure 15 c  82. Table I X Anomaloscope M i d - P o i n t s and Standard D e v i a t i o n s f o r 10X Luminance o f Exp.1. (Two f i l t e r c o n d i t i o n s . )  Red-Green E q u a t i o n  Yellow-Blue Equation  Blue-Green Equation  63+D  •31+A  ' 45+D  X  41.0  40.3  40.5  39.8  SD  1.5  1.4  0.5  1.2  X  40.0  47.3  38.8  42.6  SD  11.3  11.2  16.1  6.0  X  40.0  40.3  46.7  44.8  SD  7.2  6.4  8.5  5.2  •" EXT+D  83 Table X Means and Standard  D e v i a t i o n s f o r 100-hue Test  (Two-Filter Conditions)  3 IfA  45+B  63+C  EXT+D  0 . 3 Lux  Box 1  Box 2  Box 3  Box 4  X  103.7  70.3  112.0  68.3  SD  40.9  16.7  23.5  22.4  X  107.7  94.0  119.0  51.3  SD  69.9  33.4  9.1  30.3  X  164.0  138.0  163.3  100.0  SD  50.5  28.0  65.0  X  159.0  134.3  188.7  88.3  SD  29.7  17.6  21.9  44.9  84  The P a n e l D-15  Test  As can be n o t e d i n F i g u r e 14,  t h e r e i s a tendency  to  confuse t h e caps i n a manner c h a r a c t e r i s t i c o f t h e TRITAN Defect.  The mean-score diagrams 31-A  and E X T - D . i n d i c a t e t h e  p r o f i l e s o f the l e a s t and most dense e x p e r i m e n t a l 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  i n c r e a s e i n t h e TRITAN ERROR between t h e s e two  conditions  and, as e v i d e n c e d by the EXT-D p r o f i l e s , a l l o b s e r v e r s i n t h i s group p a i r e d caps 7 and 15, strong t r i t a n c l a s s i f i c a t i o n .  thus i n d i c a t i n g a f a i r l y  85.  The P s e u d o i s o c h r o m a t i c  Plates  I n Experiment I I s u b j e c t s made c o n f u s i o n i n b o t h the D v o r i n e and AO H-R-R t e s t s . grams o f t h e s e m i s t a k e s Dvorine t e s t  are p r e s e n t e d  seems t o be a f f e c t e d  mistakes  Frequency  histo-  i n F i g u r e 16.  The  most a t o l a t e s 9 and 1 0 ,  a l t h o u g h 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 t o be more o f t e n confused by o b s e r v e r s w e a r i n g the denser  simulation f i l t e r s .  The AO H-R-R t e s t  s c o r e s show a tendency towards b l u e - y e l l o w c o n f u s i o n . 17 and 18 t e n d t o be w e i g h t e d toward t h e t r i t a n  classification  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 a t i o n i n the h i g h - d e n s i t y group.  Plates  classifi-  The a u t h o r o b s e r v e d  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  that  and form  cues at t h e s e 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  that  c o r r e c t r e s p o n s e s were g i v e n t o some o f t h e AO H-R-R p l a t e s by t h e 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  colour.  (The f r e q u e n c y f o r group 63-C i s based on two i n s t e a d  of  t h r e e o b s e r v e r s , as one s u b j e c t d i d n o t complete t h e AO H-R-R t e s t o r t h e P a n e l D - 1 5 ) .  86  31+A  45 + B  63+C  Ext+D  j  2  3 \  4  I  -f  i  PLATE He  16«l  H lo ll Iz a *  ' 5 li i? '8 c» Jo  NUMBER  Frequency 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 on t h e AO H-R-R t e s t ( 0.31 Lux)  *7  r 31+A  r A5*B  63+C  o c Q) C7"  3  ExtO  I  2  3  H k>  45U  ii  a.  13  if  PLATE No. Figure 16 b  Frequency Histograms f o r Confusion E r r o r s on the Dvorine T e s t ( 0.31  Lux)  88. DISCUSSION I t would appear from t h e d a t a c o l l e c t e d i n E x p e r i m e n t I that the combinations  o f l e n s and m a c u l a r pigment s i m u l a -  t i o n f i l t e r s produce changes I n c o l o r v i s i o n which resemble t h o s e changes w h i c h have been a t t r i b u t e d t o a g e i n g The c o l o r m a t c h i n g d a t a shows a g e n e r a l w i d e n i n g y e l l o w - b l u e and b l u e - g r e e n Blue equation  m a t c h i n g ranges.  processes.  of the  The Y e l l o w -  seems t o be a f f e c t e d most w i t h mid m a t c h i n g  p o i n t s n o t t e n d i n g t o s h i f t towards t h e b l u e as one might expect  from t h e e x p e r i m e n t a l f i l t e r c h a r a c t e r i s t i c s .  In-  s t e a d t h e r e a p p e a r s t o be a g e n e r a l d e s c r i p t i o n o f c o l o r matching a b i l i t y .  Part o f 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 e x p l a i n e d by t h e f a c t t h a t t h e r e a r e a c t u a l l y f e w e r d i s c e r n a b l e d i f f e r e n c e s on t h e y e l l o w s i d e o f the e q u a t i o n than t h e r e i s on t h e 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 t o a f f e c t t h e y e l l o w - b l u e and b l u e - g r e e n lens f i l t e r s . evidence  e q u a t i o n s more than d i d t h e  T h i s 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  f o r t h e e x i s t e n c e o f i n c r e a s e s i n m a c u l a r pigment  due t o a g e i n g . Many s u b j e c t s a c c e p t e d  matches down t o 100% y e l l o w  f i l t e r i n the yellow-blue equation setting).  No one a c c e p t e d  (0 on t h e anomaloscope^  t o t a l l y b l u e matches.  Colour  89.  naming o f the anomaloscope ' p r i m a r i e s '  by the o b s e r v e r s  w i t h t h e d e n s e r e x p e r i m e n t a l f i l t e r s proved t o be difficult.  The b l u e - g r e e n  quite  e q u a t i o n i n p a r t i c u l a r caused  n o t a b l e c o l o u r - n a m i n g d i f f i c u l t i e s , many o b s e r v e r s changing n o t a b l e  ex-  c o l o u r - n a m i n g d i f f i c u l t i e s , w i t h many  o b s e r v e r s e x c h a n g i n g names f o r the p r i m a r y f i l t e r s  shown.  As g r a d u a l i n c r e a s e s i n the m a t c h i n g ranges can be seen t o 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 a g e i n g p o p u l a t i o n , i n c r e a s e d  matching  r a n g e s , a l o n g t h e s e same l i n e s c o u l d be p r o d u c e d by g r a d u a l selective  decreases i n ocular 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 t h e s e h y p o t h e t i c a l o c u l a r changes do n o t c o m p l e t e l y account f o r the e x t e n t o f w i d e n i n g o f t h e m a t c h i n g ranges i n v o l v i n g b l u e l i g h t found i n t h o s e age p o p u l a t i o n s w h i c h c o r r e s p o n d t o the f o u r g r o u p s mentioned h e r e i n .  experimental  T h i s p o i n t becomes more e v i d e n t  when t h e c o l o u r d i s c r i m i n a t i o n and c o n f u s i o n d a t a a r e  noted.  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 s c o r e s f o r t h e f o u r e x p e r i m e n t a 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 creasing  f i l t e r density p a i r s .  Comparing t h i s f i g u r e  V e r r i e s t ' s age d a t a ( F i g . 6a) one may n o t e the between the two l o w e r d e n s i t y c o n d i t i o n s .  with  correspondence  However, t h e r e  seems t o be more e r r o r i n V e r r i e s t ' s d a t a on the  increased  age groups than can be a c c o u n t e d f o r by o c u l a r changes a l o n e ;  90.  a t l e a s t as s i m u l a t e d i n the p r e s e n t s t u d y . d i r e c t i o n o f change appears t o be c o r r e c t .  However, t h e I f reductions  i n t h e t o t a l amount o f l i g h t were made as w e l l , correspondence might be a t t a i n e d .  further  Experiment I I attempted  t o combine t h e s i m u l a t e d r e d u c t i o n s 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 of colour v i s i o n .  investigation  Because t h e c o l o u r m a t c h i n g d a t a o f  E x p e r i m e n t 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 t h e c o l o r m a t c h i n g t a s k c o u l d c o n c e i v a b l y be seen as a l r e a d y a t reduced l e v e l .  a  I n c r e a s e s i n the luminance o f t h e i n s t r u m e n t  produced two changes i n the r e s p o n s e o f t h e e x p e r i m e n t a l observers: 1)  I n c r e a s e d luminance d e c r e a s e d the s i z e o f t h e m a t c h i n g r a n g e s , e s p e c i a l l y the y e l l o w - b l u e equation.  2)  I n c r e a s e d luminance produced a tendency toward s h i f t i n g the m i d - p o i n t towards t h e b l u e ' p r i m a r y ' .  T h i s f i n d i n g seems t o s u p p o r t V e r r i e s t ' s n o t i o n  of  the p o s s i b i l i t y of a 'mesopisation' process taking place i n the v i s u a l system, a t l e a s t from a p h y s i c a l s t a n d p o i n t . performance o f o b s e r v e r s under t h e i n c r e a s e d c o n d i t i o n c l e a r l y shows improvement.  The  luminance  I t would seem t h a t t h e  r e s p o n s e s become more p r e d i c t a b l e i n t h e p h y s i c a l terms o f t h e 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  increase.  I t would be i n t e r e s t i n g t o see t h e s e m i d - p o i n t s and m a t c h i n g ranges measured on a g e i n g o b s e r v e r s a t the i n c r e a s e d l u m i n a n c e .  91  I f the ' r o e s o p i s a t i o n '  p r o c e s s was t o be seen as  reasonable hypothesis,  a  improvement s h o u l d be n o t e d a t  h i g h e r o f the two b r i g h t n e s s  levels.  M a t c h i n g ranges s h o u l d  d e c r e a s e b u t , as w e l l , t h e m i d - m a t c h i n g p o i n t s h o u l d towards the b l u e  'primary'.-'1  the  shift  Colour 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 t o an 'early'  classification  s p e c i f i c degradation  o f the T r i t a n defect  after  that.  and f u r t h e r n o n -  The p r o f i l e s o f  under low l u m i n a t i o n are p r e s e n t e d  in Figs.  15  conditions  (a-d).  A l t h o u g h 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 c o n f u s i o n s do n o t o c c u r u n t i l 0.2 L u x ;  the observers i n the  p r e s e n t study were s c o r i n g i n a manner w h i c h would them as T r i t a n a t a minimum o f the experimental f i l t e r s .  classify  0 . 3 1 l u x w i t h the use  of  The f i r s t two c o n d i t i o n s appear  t o be t r i t a n o p i c w h i l e t h e l a t t e r two apoear a n a r c h i c .  This  breakdown i n c o l o r d i s c r i m i n a t i o n t a k e s p l a c e a t a l e v e l o f 0 . 3 1 l u x and h i g h e r .  T h i s would tenuously i m p l i c a t e  reduct-  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 e n s - m a c u l a r p i g m e n t a t i o n a possible The r e s u l t s 51.  contributor to acquired yellow-blue o f the Pseudoisochromatic  Plates  as  deschromatopsia.  i n Experiment  The e x t e n t o f t h i s s h i f t c o u l d be used as an e s t i m a t e o f t h e 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 m e d i a . P r e s u m a b l y , the measurement would t a k e 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 w a v e l e n g t h s .  II  92. r a i s e some o t h e r i n t e r e s t i n g q u e s t i o n s . f i l t e r d e n s i t y there are increased the D v o r i n e and AO H-R-R confusion  tests.  With i n c r e a s i n g  e r r o r s c o r e s on  The  both  f o u r most common  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  o f the AO H-R-R  and P l a t e s 9 and  f e l t t h a t the experimental  10 o f t h e D v o r i n e .  It i s  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 n o t o n l y c o l o r d i s c r i m i n a t i o n but r e c o g n i t i o n as w e l l .  pattern  In random p r e s e n t a t i o n s o f t h e  D v o r i n e p l a t e s f o r example, t h e  ' h e a v i l y pigmented'  observer  might s t i l l be a b l e t o d i f f e r e n c e s i n c o l o u r but n o t the f i g u r e .  As n o t e d e a r l i e r , the AO  used i n t h i s study  H-R-R  showed some Darts o f f i g u r e s w h i c h were  s e t number o f g e o m e t r i c a l  observer's  identify  test editions  s l i g h t l y d i s c e r n a b l e by f o r m c o n t r a s t s w i t h t h e The  18  f i g u r e s used i n c r e a s e s  chances o f c o r r e c t g u e s s i n g ;  straight l i n e perceived  surround. the  f o r example a  i n t h e 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 o r a square e t c .  I t would seem from the o b s e r -  v a t i o n s of the author that responding to a stimulus i n a manner w h i c h r e q u i r e s some form o f v e r b a l r e c o g n i t i o n o f t h e m e a n i n g f u l n e s s o f t h e s t i m u l u s 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 m e t e r s as i n the 100 hue  test.  o f the s t i m u l u s  Many s u b j e c t s 'saw'  paradiffer-  ences a t t h e reduced i l l u m i n a t i o n l e v e l s but were u n a b l e t o s t a t e what t h e s e d i f f e r e n c e s were.  Of course a n y t h i n g ,  but  K>  M  6b  JO  »D  ?0  fV\ , to  ZO  X>  40  So  to  ?B  8»  ^ 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 i n c r e a s i n g p a i r s of simulation f i l t e r s 100 l u x .  94. b u t t h e 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 m i s t a k e i n t h e 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 o f t h i s s c o r i n g p r o c e d u r e . In terms o f t h e g e n e r a l i z a b i l i t y o f t h e s e f i n d i n g s t o a g e i n g p r o c e s s e s , i t seems t h a t both s e l e c t i v e a b s o r p t i o n o f l i g h t and r e d u c t i o n s i n i l l u m i n a t i o n a r e needed t o e x p r e s s the a g e i n g parameters i n p h y s i c a l terms.  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Wavelength t s i n g l e c e l l . conditions)  390  A .1  B .14  C  ..25  D  .34  31 .07  45 .18  63 .84  EXT 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  .26  490  .14  .32  .42  .60  .01  .04  .06  .13  500  .09  .22  .23  .36  .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  continued  (two c e l l  A-31  A-45  A-63  390  .17  .28  94  400  .20  .30  •. 9 4  410  .21  .31  420  .22  430  A-EXT  conditions) B-31  B-45  B-63  B-EXT  .21  .32  .98  1.38  1.34  .25  .35  .99  1.39  .91  1.30  .26  .36  .96  .30  .82  1.21  .34  .42  .94  1.35 1.33  .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  .04  .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  .  1.34  Appendix A c o n t ' d C-EXT  D-30  D-45  D-63  D - E X T  1.00 .  1.49  .41  .52  1.18  1.58  .47  1.11  1.51  .47  .57  1.21  1.61  .51  .51  1.11  1.50  .54  .64  1.24  1.63  420  .48  .56  1.08  1.47  .64  .72  1.24  1.63  430  .53  .60  .96  1.38  .69  .76  1.12  1.54  440  .55  .61  .83  1.35  .76  .82  1.04  1.54  450  .62  .67  .81  1.19  .81  .86  1.00  1.38  460  . 61  .65  .71  1.03  .78  .82  .88  1.20  ,470  .51  .55  .59  .84  .69  .73  .77  480  .50  • .53  .57  .75  .69  .72  .74  .94  490  .43  .46  .48  .60  .61  .64  .66  .78  500  .29  .32  .33  .44  .37  .40  .41  .52  510  .15  .17  .19  .26  .19  .21  .23  .30  520  .08  .10  .12  .17  .09  .10  .13  .18  530  .04  .04  .08  .12  .04  .04  .08  .12  540  .03  .03  .07  .10  .03  .03  .07  .10  550  .02  .02  .06  .09  .02  .02  .06  .09  C-31  C-45  390  .32  .43  400  .37  410  C-63  1.02  Appendix A cont'd  C-31  C-45  C-63  -C-EXT  390  .32  .43  1.00  1.49  400  .37  .47  1.11  410  .51  .51  420  .48  430  D-30 .41  D-45 .52  D-63 1.13  D-EXT 1.58  1.51  .47  .57  1.21  1.61  1.11  1.50  .54  .64  1.24  1.63  .56  1.08  1.47  .64  .72  1.24  1.63  .53  .60  .96  1.38  .69  .76  1.12  1.54  440  .55  .61  .83  1.35  .76  .82  1.04  1.54  450  .62  .67  .Bl  1.19  .81  .86  1.00  1.38  460  . 61  .65  .71  1.03  .78  .82  .88  1.20  470  .51  .55  .59  .84  .69  .73  .77  1.02  480  .50  .53  .57  .75  .69  .72  .74  .94  490  .43  .46  .48  .60  .61  .64  .66  .78  500  .29  .32  .33  .44  .37  .40  .41  .52  510  .15  .17  .19  .26  .19  .21  .23  .30  520  .08  .10  .12  .17  .09  .10  .13  .18  530  .04  .04  .08  .12  .04  .04  .08  .12  540  .03  .03  .07  .10  .03  .03  .07  .10  550  .02  .02  .06  .09  .02  .02  .06  .09  

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