Understand types of hereditary color vision deficiencies. Understand the physiology of color vision deficiencies (spectral sensitivity, wavelength discrimination and saturation) Understand the replacement model of dichromacy. Understand color confusion lines, color discrimination, and labelling associated with color vision deficiencies. Understand the differences between hereditary and acquired color vision deficiencies. Understand the transmittance pattern of X-linked red-green defects. Understand the Kollner’s rule and its exception to color vision deficiencies.

1. Color Vision Defect
Dr Gauri Sr Shrestha
Lecturer, MMC, IOM, TU

2. Learning objectives
• Understand types of hereditary color vision deficiencies.
• Understand the physiology of color vision deficiencies (spectral
sensitivity, wavelength discrimination and saturation)
• Understand the replacement model of dichromacy.
• Understand color confusion lines, color discrimination, and labelling
associated with color vision deficiencies.
• Understand the differences between hereditary and acquired color
vision deficiencies.
• Understand the transmittance pattern of X-linked red-green defects.
• Understand the Kollner’s rule and its exception to color vision
deficiencies.

3. Pretest- MCQs
Q1. The most common type of
color vision defect is:
• A) Monochromacy
• B) Deuteranomaly
• C) Tritanopia
• D) Protanopia
Q2. Protanopia is a type of color
vision defect associated with:
• A) Red defect
• B) Blue defect
• C) Green defect
• D) Yellow defect

4. Pretest- MCQs
Q3 Deuteranomaly primarily
affects the perception of which
colors?
• A) Red and yellow
• B) Blue and green
• C) Red and green
• D) Yellow and blue
Q4. Tritanopia is a rare color
vision defect affecting the
perception of which colors?
• A) Red and green
• B) Blue and yellow
• C) Red and yellow
• D) Green and blue

5. Pretest- MCQs
Q5. Color vision defects are more
common in men than in women
because:
• A) Men have more rod cells than
cone cells
• B) The defect is carried on the Y
chromosome
• C) Men have only one X
chromosome
• D) Women have better overall vision
Q6. Which type of color vision
defect is characterized by the
inability to perceive any color,
seeing everything in shades of gray?
• A) Deuteranopia
• B) Protanopia
• C) Monochromacy
• D) Tritanopia

6. Pretest: true/false statement
1. Color vision defects are more common in females than in males.
(True/False)
2. People with deuteranopia cannot distinguish between red and green
colors. (True/False)
3. Tritanopia is a rare type of color vision defect affecting the perception
of blue and yellow colors. (True/False)
4. Color vision defects can be completely corrected with glasses or
contact lenses. (True/False)

7. Background
• Color vision deficiency (CVD) is the decreased ability to see
color or difference in color.
Types of color vision deficiency
• Monochromacy: Only one pigment type is present
• Dichromacy: Only two pigment types are present
• Anomalous trichromacy: All three pigment types are present

8. Monochromacy
• Monochromacy non-
progressive complete color
deficiency (blindness)
• Patients with monochromacy
perceives objects with shades
of gray and use other cues to
label colors.
• These patients match any
wavelength in the spectrum
by changing the intensity of
another wavelength.

9. Monochromacy
• Rod monochromats: the
most common type,
affecting 10 in 1 million
people
• No cones, extremely poor
visual acuity.
• Blue cone monochromats:
colorblindness in photopic
and scotopic conditions
• Narrow range of color
perception in mesopic
conditions
700
ROD
L
M
S
Rod
Monochromats
Normal spectral sensitivity of retinal
photoreceptors

10. Dichromacy: One of three cones is missing or not
functioning.
• Protanopia
• Missing or defective L-
cones; x-linked
• 1% males, 0.02%
females
• Individuals see short-
wavelengths as blue
• Neutral point occurs at
492 nm
• Above neutral point,
they see yellow.

11. Dichromacy
• Deuteranopia
• Missing or defective M –
cones; x-linked
• 1% males, 0.01% females
• Individuals see short-
wavelengths as blue
• Neutral point occurs at 498
nm
• their brightness vision is
more like that of color-
normal.
• Above neutral point, they see
yellow.

12. Dichromacy
• Tritanopia
• Missing or defective S – cones;
autosomal dominant
• 0.002% males, 0.001% females.
• Individual see short-
wavelengths as green
• Neutral point occurs at 570
nm.
• Above neutral point they see
red.
chrome-extension://gphandlahdpffmccakmbngmbjnjiiahp/http://courses.washington.edu/psy333/lecture_pdfs/Week7_Day2.pdf

13. Neutral Points
• The wavelength where the
two remaining pigments
crosses.
• Colors look very
desaturated and whitish at
that point.
• Patients cannot
distinguish colors at this
area of the spectrum.
• Colors at this wavelength
are perceived as gray.
570

14. Anomalous Trichromacy - three pigment types, reduced
spectral sensitivity of one cone type. There is no neutral point.
• Protanomaly –
• Shifted red pigments, red-weakness, red-pale
• Red, orange, yellow and yellow-green appear somewhat
shifted in hue towards green.
• Violet or lavender color appears bluish.
• In dazzling sunlight or rain or fog, blinking red traffic light
from blinking yellow may not be appreciable.
• Incidence 1% males.

15. Anomalous Trichromacy
• Deuteranomaly
• Shifted green pigments, green-weakness, green-pale
• Red, orange, yellow and yellow-green appear somewhat
shifted in hue towards red.
• No loss of brightness unlike in protanomaly.
• Incidence 5% males.
• Tritanomaly
• Shifted blue pigment
• Will be hard to tell the difference between blue and green
and between yellow and red.

16. Hereditary Color Vision Defects
DEFECT PREV. IN MALES TRANSMISSION
Deuteranopia 1% X-linked recessive
Protanopia 1% X-linked recessive
Deuteranomaly 5% (Most Common) X-linked recessive
Protonomaly 1% X-linked recessive
Tritanopia &
tritanomaly
.005% (Most Rare) Autosomal
Dominant

17. Physiology of color
vision deficiency
Replacement model of
dichromacy
• Missing photopigment is replaced
by a remaining photopigments
• Deuteranope: missing green
cones are replaced by red-cones
• Protanope: missing red cones are
replaced by green cones
• Exception: missing blue-cones are
not replaced by another
photopigment
Deuteranomal
y:
M-cone
displaced
toward long
wavelengths
Protanomaly:
L-cone displaced
toward short
wavelengths

18. Spectral sensitivity: Chromaticity
440nm
520nm
620nm
570nm 530nm

19. Spectral sensitivity: Luminance function
Protanopes can
not see light of
wavelength
above 660nm

20. Wavelength discrimination
Both Protanope and
Deuteranope
• Well developed wavelength
discrimination at 490 nm
• Wavelength discrimination is
poor beyond 545 nm
• Color identification just based
on wavelength is not possible
beyond 545 nm.
• Color detection is still possible
beyond 545 nm using stimuli of
4
9
0
5
9
0

21. Wavelength Discrimination
• Well developed color
discrimination at longer
wavelength
• Poor wavelength
discrimination at
495nm

22. Saturation
• Neutral point: desaturated
appearance of spectral
stimuli at specific
wavelength
570nm

23. Saturation

24. Color confusion lines
•Protanopia
• Protanopes' confusion lines converge at a
point at the red end (right end) of the
spectrum locus
• Essential monochromat above 545nm.
• For both protanopes and deuteranopes, one
isochromatic line lies on the spectrum locus
from 540 nm to 700 nm
• In stead of 150 wavelengths, protanopes can
see only 17 different wavelengths.
• Difficult to distinguishing between red and
green colors.

25. Color confusion lines
• Deuteranopia
• Deuteranopes' confusion lines run
through an extra-spectral point (off
the chart to the lower right)
• Dichromats are essentially
monochromats above 545 nm.
• Green is seen as reddish purple.
• In stead of 150 wavelengths,
deuteranopic candidate can see only
27 different wavelengths.

26. Color confusion lines
• Tritanopia
• Tritanopes confuse colors (of the
same brightness) that lie along
lines passing through a point near
the blue end of the spectrum locus
in the xy diagram
• Difficult to distinguishing between
blue and green colors and
between yellow and violet.

27. Practical implication

28. Color discrimination and labeling
• Color labeling is remarkably good in color vision deficiency.
• However, Industrial color labeling is difficult, such as
stripe/pattern analysis.

29. Color discrimination and labeling

30. Color Vision and Females
• Tend to be carriers
• Tend to have normal color vision
• 20 times less likely to have a color vision deficiency

31. Transmission of X linked, red-green defects
from parents to offspring
X X
X XX XX
Y XY XY
Father Normal (XY)
Mother Normal (XX)
X X
  X  X
Y XY XY
Father Defective ( Y)
Mother Normal (XX)
Daughters Carrier
Sons Normal
 
X  X  X
Y  Y  Y
Father Normal (XY)
Mother Defective ( )
Daughters Carrier
Sons Defective

32. Transmission of X linked, red-green defects
from parents to offspring
 X
    X
Y  Y XY
 X
X  X X X
Y  Y XY
Father Normal (XY)
Mother carrier ( X)
Daughter: 1 carrier, 1 normal
Sons: 1 defective, 1 normall
Father Defective ( Y)
Mother Carrier ( X)
Daughters: 1 carrier, 1 defective
Sons: 1defective, 1 Normal

33. Congenital vs. Acquired
CONGENITAL ACQUIRED
Affects both eyes equally One eye only OR asymmetric
Usually a R-G defect B-Y OR R-G
Other visual functions normal Other visual functions abnormal
Stable through lifetime Variable, dependent on test and diseases conditions
Learned to adapt-can label
objects
Cannot name color correctly
More prevalent in male Equally prevalent in male and female
Not associated diseases or
toxicity
Classification not straightforward with standard
clinical color test

34. Kollner’s Rule
Location Defect condition
Media B-Y Nuclear sclerosis
Outer retina B-Y AMD, DR
Inner retina R-G Optic atrophy, toxic amblyopia
Pathway R-G Lesions
• Outer retinal diseases and media changes result in blue-yellow color vision
defects
• Inner retina, optic nerve visual pathways and visual cortex diseases result in
red-green defects

35. Exception
to The
Kollner’s
Rule

36. Summary
• Defective color vision, or color blindness, is a condition where
individuals have difficulty distinguishing certain colors.
• Protanopia and Protanomaly: problems with red cones
• Deuteranopia and Deuteranomaly: problems with green
cones
• Tritanopia and Tritanomaly: Issues with blue cones
• Complete Color Blindness (Achromatopsia): Inability to
perceive any color.
• Causes: genetic inheritance (most common), diseases,
medications, and exposure to chemicals

37. Thank you