colour vision &theories colour vision test( in next) pptx including ,defination detail description of theories conclusion of theories,absorption of conepigments graph Reference from{ ak khuranka} book(optometry)

1. THEORIES OF COLOUR
VISION
REPRESENTED BY-
ABHAY KOUNDAL
BSC OPTOMETERY 2ND YEAR
@Mmu solan

3. 1) DEFINATION
2) THEORIES OF COLOUR VISION
3) TESTS FOR COLOUR VISION
1)DEFINATION-
• Ability of the eye to discriminate b/w different colours excited by
light of different wavelengths
• colour vision is the function of cones
• better apperciated In photopic vision
• In dim light scotopic vision all colour are seen gray
•Phenomennon is known as purkinje shift

4. PHOTOPIC &SCTOPIC VISION
PHOTOPIC VISION
• Vision of eye under well light
• Uses cones & provide colour
• Provide the eye colour
sensitivity
SCTOPIC VISION
• Vision of eye under dim light
• Uses only rods to see objects
• Object appear in black &white

5. THEORIES OF COLOURVISION
• There are mainly 2 theories of colour vision
•Trichromatic theory
•Opponent theory of hering

6. TRICHROMATIC THEORY
• Suggested by young & subsequently
• Modified by Helmholtz ,hence called Young Helmholtz theory
•It postulates the existance of 3 kinds of Cones
Each containing a different photopigment which is
maximally sensitive to one of 3 primary colour
red , green, blue
Sensation of any given colour is determined by relative
frequency of the impulse from each of the cone system

7. ADDITIONAL DATA
• Given colour consist of a admixture of 3 primary colours in
different proportion
• Correctness of the youngs helmholtzs trichromatic theory is
demonstrated by identification & chemical characterisation of each
of 3 pigments by recombinant dna techmique
•Each having different absorption
spectrum

8. SENSITIVE CONE PIGMENT
RED SENSITIVE
CONE PIGMENT
• Known as
Erythrolabe
• Long wavelength
sensitive
• Absorbs
maximally in a
yellow portion
with a peak at
565nm
GREEN SENSITIVE
CNE PIGMENT
• known as
chlorolabe
• Medium
wavelength
sensitive
• Absorbs
maximally in
green portion
peak at 535nm
BLUE SENSITIVE
CONE PIGMENT
• Known as cyanolabe
• Short wavelength
sensitive
• Absorbs maximally in
the blueviolet portion
og he spectrum with a
peak at 440nm

9. ABSORPTION SPECTRUM OF 3 CONE PIGMENTS

10. CONCLUSION
• Blue green & red are primary colours
•But cones with their maximally sensitivity in the
•Yellow portion of the spectrum are at lower thresh hold than
green
•Rhodopsin Is located on chromosome 3
•Gene for the blue sensitive cone is located at chromosome 7
•Red & green sensitive cones are arranged on the q
arm of x chromosome

11. OPPONENT COLOUR THEORY OF HERING
• Some colours are appear to be mutually exclusive
•There is no such colour as reddish green & such
phenomenon can be difficult to explain on the basis of
trichromatic theory alone
• Both theories are usefull in that :
• Colour vision is trichromatic : at the level of photoreceptor
• Colour opponency occurs at ganglion cell onward :
• Acc to opponent theory there are 2 main types of colour opponent
colour ganglion cell

12. OPPONENT GANGLION CELLS
• Red green opponent colour
cells
• Use signal from red & green
cones to detect red/green
contrast within their field
• Blue yellow opponent colour
cells
• Obtain a yellow signal from
the summed output of red
&green cones
• Contrasted with the Output
from blue cones within the
field

13. THANK YOU