2. • COLOR VISION
• COLOR VISION THEORIES
• COLOR VISION DEFECTS
• COLOR VISION TESTS
INTRODUCTION
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3. Color vision
• Perception of color by the pigments of cone
according to the genetic code
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4. Characteristics of color vision
• Hue :- capacity of the eye to discriminate
between the adjacent wavelength
• Brightness:- depend on luminous flux
• Saturation :- it measure the minimum
quantity of given wavelength that must be
added to the white light for change in
appearance to be detected
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5. Theories of color vision
1. Additive color theory
2. Subtractive color theory
3. Thomas Young theory
4. Young Helmholtz theory
5. Herring's opponent theory
6. Tetrachromatic theory
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6. Additive color theory
• Based on 3 primary color – red , green & yellow
• Mixture of 2 primary color give rise to secondary
color
A+B=Y (Yellow)
A+C=M (Magenta)
B+C= C (Cyan)
A+B+C=W (White)
W
RED
GREEN
BLUE
M C
A
C
B
Y
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8. Thomas Young theory
• For every color one nerve fiber present in the
retina
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9. Young Helmholtz theory
• 3 cone photoreceptors on the retina which is
sensitive to different wavelength
Erythropsin
Chloropsin
Cyanoipsin
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10. Herring’s opponent theory
• Based on 4 primary colors – Red, Green, Blue &
Yellow arranged in opponent pairs
Red – Green
Yellow -Blue
White- Black
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11. Tetrachromatic theory
• Based on 4 primary colors – Red, Green, Blue &
Yellow
• Yellow is not a combination of Red & Green
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12. Color vision deficiency
• Lack of any color sensation
• It effects either the photoreceptor or the channels
results in the ability to discriminate color
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13. Consequences of color deficiency
• The retina is made of rods and cones .
• The rods give us night vision
• Cone give us color vision & day vision
• Each cone contains light sensitive pigments.
• Gene contains coding instruction for these
pigments .
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14. Consequences of color deficiency
• If the coding instructions are wrong the
wrong pigments will be produced.
• And the cone will be sensitive to different
wavelength of light.
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15. Types of color vision deficiency
1. Congenital color vision deficiency
2. Acquired color vision deficiency
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16. Trichromatism:all three systems are present
Dichromatism: one system is absent.
Monochromatism:two system are absent
The three systems are :
Red ,Green & Blue.
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17. Classification of color Vn defect
Congenital Acquired
Anomalous
trichromatism
Dichromatism Monochromatism
Protenomaly
Deuteranomaly
Tritanomaly
Protanopia
Deutranopia
Tritanopia
Rod monochromatism
Cone monochromatism
Type 1 R-G
deficiency
Type 2 R-G
deficiency
Type 3 B-Y
deficiency
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18. Anomalous trichromatism
• People with anomalous trichromat vision
use all three color receptors but reception of
one pigment is misaligned.
1. Protanomaly: reduced red sensitivity
2. Deuteranomaly: reduced green sensitivity
3. Tritanomaly: reduced blue sensitivity.
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19. Dichromatism
• People with dichromatism use only two of the
three visual pigments.
1. Protanopia: unable to receive red.
2. Deuteranopia: unable to receive green.
3. Tritanopia: unable to receive blue.
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20. Monochromatism
• Two type
1. Rod monochromatism- decrease visual acuity
nystagmus, central scotoma & photophobia
2. Cone monochromatism- normal visual acuity
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21. Acquired color vision defect
• There are 3 types
1. Type -1 red-green deficiency
2. Type -2 red-green deficiency
3 . Type -3 blue-yellow deficiency
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23. Clinical test for color vision assessment
1. Pseudo-isochromatic plate
• Ishihara color Vn chart
• AOHRR plate
2. Arrangement test
• Farnsworth Munsell – 100 hue test
• Farnsworth D-15 test
3. Anamoloscope
• Nagel’s anamoloscope
4. Occupational test
• Lantern test
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24. Ishihara color vision chart
• Based on the color confusion
(Pseudoisochromatism)
• Each pseudoisochromatic plate is crowded
with colored spots
• Use to determine red -green deficiency
• Available in 16, 24 & 38 plates
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25. 1. Demostration plate (1)
• 12 no. plate
• Both normal & color Vn defect pt. can read
2. Transformation plate (2-9)
• 8, 6, 29, 57, 5, 3, 15 & 74
• Normal person can read correctly
• Red – green deficiency person can read them as
3, 5, 70, 35, 2, 5, 17 & 21
• Total color Vn defect person can’t read any no.
Ishihara color vision chart
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26. 3. Vanishing plate (10-17)
• 2, 6, 97, 45, 5, 7, 16 & 73
• Normal person will read correctly
• Red– green deficiency person not able to read
( either completely or incompletely )
• Total color Vn defect person can’t read any no.
Ishihara color vision chart
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4. Hidden plate (18-21)
• 5, 2, 45 & 73
• Normal & total color Vn defect person not able
to read any no.
• Red –green deficiency person will read correctly
Ishihara color vision chart
Jennifer Birch Diagnosis of
defective color vision pg 56
28. 5. Diagnostic plate (22-25)
• 26, 42, 35 & 96
• Normal person able to read correctly
• Strong protenomaly & protenopia read only
6, 2, 5 & 6
• For mild protenomaly - 6, 2, 5 & 6 are clearer
than other
• Strong deuteranomaly & deutranopia read only
2, 4, 3 & 9
• For mild deuternomaly -2, 4, 3 & 9 are clearer
than other
Ishihara color vision chart
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29. Protan & deutran deficiency
Ishihara color vision chart
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30. 6. Tracing plate (26-38)
• It contains the pathways
• It is use in illiterate person & children
Ishihara color vision chart
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31. Analysis of result
• Normal – if the 17 or more plate are read correctly
• Color Vn defect – if the 13 or less than 13 plates
are read
• Repeat test – if between 13-17 plates are read
Ishihara color vision chart
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32. Method for ishihara color vision test
• Good room Illumination as day light.
• Patient should wear appropriate spectacle
correction & occlude one eye.
• The test plate is held at a distance of 75cm.
• Plane of the plate & line of the sight of vision
should be perpendicular ( tilted 45˚)
• Ask to patient to read the plates.
• For illiterate pt. ask to trace the line between
two X’s.
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33. American Optical Hardy Rand
Rittle Plate (AOHRR)
• Based on pseudoisochromatic test
• To determine red green and blue yellow color
vision defect
• Consist of 24 plates with vanishing design
containing geometrical shape
• 4 introducing plates ,6 screening plate,10 plates
for grading severity of protan &deutan, 4 plates
for grading severity of tritan defect
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34. Holmgren Wool Test
• Based on color matching
• the aim is to determine isochromatism color
confusion by encouraging child to select wool
sample which appears similar in hue
• 3 test skeins yellow-green, pink & red
• Wools are placed on gray surface & person select
matching shades for each test skeins
• Viewing time of 1min
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36. Farnsworth-Munsell 100 hue test
• It provides most sensitive assessment of hue
discrimination
• It is use for red-green & blue-yellow deficiency
• Four 20˝×1.75˝×1.25˝ trays, housed in a
21.5˝×6.12˝×2.5˝ carrying case
• Total of 85 numbered disks with varying hues
• Color reference size is 7/16˝ diameter
• Each disk is numbered to facilitate scoring
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38. Farnsworth D –15 test
• It is use for red-green & blue-yellow deficiency
• Capable of detecting moderate to severe color vision
deficiency
• Contains a 12 mm reference cap & 15 numbered
disks with all different hues
• Caps which substends an angle of 1.5 degree at 50
cm
• The patient’s task is to arrange the colored caps in
order compared to the reference cap
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40. Anomaloscope
• Based on color match known as Rayleigh equation
R+G=Y
• it is use to determine red-green defect
• On the instrument monochromatic yellow light is
presented in half of a 2˚ circular field & a mixture of
monochromatic red-green light is presented in other
half
• Patient tasks is to match mix spectral red green lights
to other half the yellow light
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41. Nagel’s Anamaloscopes
• 2 knobs : one changes the brightness of yellow &
other changes the mixture of red & green
• The matching range recorded from matching
limits obtained on red/green mixture scale
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43. Lantern test
• Light used are either red,green or white
• Two light are presented at a time in any combination
• Call out immediately name of the color 1st top then
bottom
• Nine pairs of lights are presented
• Test is failed if the average error on last 2
administration is >1
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