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1. Colour Vision
MOPA 022

2. Definition
Colour vision is the ability to perceive differences in the
composition of wavelengths
Perception of colour depends upon spectral composition of light:
◦ coming from an object &
◦ emanating from surrounding
◦ State of light adaptation of subject
Colour vision can be described as a subjective perception or
sensation
Black and white are not colours

3. Colour Sense
Ability of the eye to discriminate between different colours excited
by light of different wavelengths
Function of cones
These cones have light-sensitive pigments that enable us to
recognize colour
Found in the macula (the central part of the retina), each cone is
sensitive to either red, green or blue light

4. Colour Sense
The cones recognize these lights based on their wavelengths
Better appreciated in photopic vision
In scotopic vision all colours seen as gray-called Purkinje shift

5. Colour Sense
Visual Spectrum 360nm –
760nm
L cones long (560nm) Red light
M cones medium (539nm) Green
light
S cones short (430nm) Blue-
violet light
Defects can be congenital or
acquired
Males > Females B/Y > R/G

6. Colour Deficiency
Usually, is an inherited condition caused by a common X-linked
recessive gene
Passed from a mother to her son, about 8% of white males are
born with some degree of colour deficiency
Women are typically carriers of the colour-deficient gene,
approximately 0.5% of women have colour vision deficiency
Disease or injury that damages the optic nerve or retina can also
cause loss of colour recognition

7. Colour Deficiency
Severity of inherited colour vision deficiency generally remains constant
throughout life
The most common form of colour deficiency is red-green.
Most people with colour vision deficiency can see colours, they simply
have a harder time differentiating between them, which can depend on
the darkness or lightness of the colours
Another form of colour deficiency is blue-yellow
Rarer and more severe form of colour vision loss than just red-green
deficiency because people with blue-yellow deficiency frequently have
red-green blindness, too

8. Colour Deficiency
In both cases, people with colour-vision deficiency often see
neutral or gray areas where color should appear
People who are totally colour deficient, a condition called
achromatopsia, can only see things as black and white or in shades
of grey
Colour vision deficiency can range from mild to severe, depending
on the cause
It affects both eyes if it is inherited and usually just one if it is
caused by injury or illness

9. Colour Deficiency
Congenital color deficiencies are caused by inherited photopigment
abnormalities. One, two, or three cone pigments may be missing or
one of the three types of cones may contain a photopigment that
differs significantly in spectral sensitivity compared to the normal
photopigment

10. Colour Deficiency
Congenital color vision defects Acquired color vision defects
Present at birth Onset after birth
Type and severity of the defect the same
throughout life
Type and severity of the defect fluctuates
Type of defect can be classified precisely Type of defect may not be easy to classify.
Combined or non-specific defects frequently occur.
Both eyes are equally affected Monocular differences in the type and severity of
the defect frequently occur
Visual acuity is unaffected (except in
monochromatism) and visual fields are
normal
Visual acuity is often reduced and visual field
defects frequently occur
Predominantly either protan or deutan Predominantly tritan
Higher incidence in males Equal incidence in males and females

11. Colour Deficiency
The terms protan, deutan, and tritan represent the color
deficiencies involving the absence or abnormality of a single
photopigment (dichromats and anomalous trichromats)

12. Colour Deficiency
Number of cone
photopigments
Type / Denomination Hue discrimination
None Typical or rod monochromat Absent
One Atypical, incomplete, or cone
monochromat
Absent
Two Dichromat
(protanope, deuteranope, tritanope)
Severely impaired
Three (one
abnormal)
Anomalous trichromat
(protanomalous, deuteranomalous,
tritanomalous)
Mildly to severely impaired
(continuous range of severity)
Three Normal trichromat Optimum

13. Colour Vision Tests
There are different types of tests that can be used to assess colour vision:
 Colour Arrangement
oFarnsworth-Munsell D-15 hue test (hue discrimination test)
oFarnsworth 100- hue test
Pseudo-Isochromatic Plates
oIshihara pseudo-isochromatic plates
oHardy Rand Rittler pseudoisohromatic plates (HRR)
Colour matching
oNagel Anomaloscope

14. Farnsworth-Munsell D-15
15 caps, 1 pilot
PROCEDURE
50cm
Instructions: “The objective of the test is to arrange the caps in
order according to colour. Please transfer them onto the panel
without turning them over. Place them so they form a regular colour
sequence based on the previous cap starting with the pilot cap. It
should take you about 2 minutes however accuracy is more
important than speed”

15. Farnsworth-Munsell D-15
Recordings
Crossings – dx caps placed together
Placement errors – adjacent caps swopped
Fail - 2 or more crossings, 3 or more placement errors

16. Farnsworth-Munsell D-15

17. Farnsworth 100- hue test
4 wooden cases, 85 moveable caps, 2 pilots each box
Open the case lengthwise before the patient. The cases themselves
can be presented in any order however the caps should be
presented in random order.
Instructions: “The objective of the test is to arrange the caps in
order according to colour. Please transfer them onto the panel
without turning them over. Place them so they form a regular colour
sequence between the two caps (indicate). It should take you about
2 minutes however accuracy is more important than speed”

18. Farnsworth 100- hue test
Calculate: Dx score, Error score, Total Error Score
Dx Score: involves the actual position of the cap. Look at the
adjacent caps. (add difference)
Error Score: Dx score – 2
Example: Px placed caps as follows: 1, 2, 3, 4, 6, 8, 5
◦ Dx score of cap 3 : Which caps are on either side of 3? 4 and 2
What is the absolute value difference between 3 & 2 = 1 (3-2=1)
and 3 and 4 = 1 (4 - 3 = 1) dx score = 1 + 1 = 2

19. Farnsworth 100- hue test
Error score = distance score – 2 Thus the error score for cap 3 = distance
score of cap 3 – 2
◦ 2 – 2 = 0
Notice cap 3 is actually in the correct place with 2 and 4 on either side.
When caps are placed correctly like this the error score =0
What is the distance and error scores for cap 6?
◦ Dx score (6 is next to 4 and 8) 6-4 = 2, 8-6 = 2
◦ Dx score = 2+2= 4
◦ Error score = dx score – 2
◦ 4-2 = 2

20. Farnsworth 100- hue test
Add the error scores.
For EACH cap work out the error score. Add the error scores and look at the
norms below
TOTAL ERROR SCORE
o< 30 yrs normal if error score <100
o> 30 yrs normal if error score <120
Example: Px is 25 years old with total error score = 120.
oSince px is younger than 30 for her to be normal the total error score should
be less than 100 but it is 120, Therefore, px has deficient colour vision.

21. Farnsworth 100- hue test
You need to look at the record sheet
Remember the 100 hue test is based on different colours that can
be placed in a circle orientation (ie. If all caps are correct on your
record sheet you will see a circle)
On the vertical axis the dx scores for each cap is plotted
You will notice the lowest value on the vertical axis is 2, since a dx
score of a correctly placed cap is 2.
And each cap is represented at the centre in the circle.

22. Farnsworth 100- hue test
First we need to find the cap number and plot its associated dx
score.
Plot the dx score for each cap
Then you will have a page filled with 85 dots
Join the dots and see where the highest spike of the formation is
What direction is the highest spike in relation to the axis of
deutan/protan/tritan?

23. Farnsworth 100- hue test

24. Ishihara pseudo-isochromatic plates
1 Introduction Seen correctly by all observers. Demonstrates the visual
task. Identifies malingerers.
2-9
Transformation
Screening A number is seen by colour normals and a different number
is seen by red-green colour deficient. Sometimes colour-
deficient people see no number
10-17
Vanishing
Screening A number is see by colour deficient but cannot be seen by red-
green colour deficient
18-21
Hidden digits
Screening A number cannot be seen by normals but can be seen by red-green
colour deficient. (These plates have poor sensitivity and
specificity and should be omitted)
22-25
Classification
(Used when screening plates
identify colour deficiency)
Classification of
protan and deutan
deficiency
Protans only see the number on the right side of each plate and
deutans only see the number on the left.

25. Ishihara pseudo-isochromatic plates

26. Ishihara pseudo-isochromatic plates
Present plates to patient and ask them to identify the numbers
they see
If 13 or more plates are correctly identified then the patient has
normal colour vision.
If 9 or less plates are identified then the patient is regarded as
colour deficient.
Those patients who are able to read plates 14 and 15 as numerals 5
and 45, and read them easier than plates 10 and 9 are regarded as
having a red-green colour vision defect

27. Hardy Rand Rittler (HRR)
Provides several very important features to provide the most
advanced colour vision test available
Congenital and acquired testing
Identification of the type of defect and diagnosis of the extent of
the defect
As well as quick positive classification of normals.

28. Hardy Rand Rittler (HRR)
As well as quick positive classification of normals.
Employ a sophisticated test strategy that virtually eliminates the
potential for memorization and malingering.
The figures used by the plates are independent of language
Suitable for both adults and children

29. Hardy Rand Rittler (HRR)
Procedure:
The HRR Pseudoisochromatic Plate Test supports very efficient
colour deficiency screening
The first four plates are used to show the patient how the test
works
The fourth plate in this demonstration series has no figure and
serves to potentially uncover attempts to memorize this test.

30. Hardy Rand Rittler (HRR)
The next six plates (screening series) present the most difficult
protan, deutan and tritan (red, green, yellow, and blue) targets
Success with these plates defines the subject as having normal
colour vision 1 and completes the test
The subsequent 14 plates are the diagnostic series and provide
diagnostic as to the extent (mild, medium or strong) and type of
defect (Protan, Deutan, Tritan).

31. Hardy Rand Rittler (HRR)

32. Hardy Rand Rittler (HRR)
Begin the testing with the screening plates (5-10) at 75cm.
Turn to plate 5 and ask, “How many colored symbols do you see here?”
Then ask, “What are they?” Then ask, “Where are they?”
It is important to obtain an IMMEDIATE response as to the number of
symbols seen.
No revision of the patient’s opinion on this point is allowed.
Record the patient’s response (using X, O) in the box provided for Plate 5
on the Scoring Sheet, recording the exact symbols seen in the location
indicated by the patient. If the patient’s reply to all three questions is
correct, then place a tick mark beside the box to indicate a correct
response

33. Hardy Rand Rittler (HRR)
If, on the other hand, the patient makes an error in answering any
one of the three questions, no tick mark is made.
Proceed in a similar fashion with plates 6-10, turning the pages at
about 3- second intervals, asking the patient to answer the same
three questions as each page is turned.
This completes the screening test.
If all six boxes are checked to show correct responses, the patient
has normal color vision and no more testing need be done.

34. Hardy Rand Rittler (HRR)
If plates 5 or 6 are not checked, the patient has defective blue-
yellow vision and the examiner proceeds to show plates 21-24.
If any of plates 7-10 are not checked, the patient has defective red-
green vision and the examiner proceeds to show plates 11-20.
If any plates of both screening groups (5-6 and 7-10) are not
checked, all remaining plates (11-24) must be given

35. Treatment
There is no cure for inherited colour deficiency
If the cause is an illness or eye injury, treating these conditions may
improve colour vision
Using specially tinted eyeglasses or wearing a red-tinted contact
lens on one eye can increase some people's ability to differentiate
between colours, though nothing can make them truly see the
deficient colour.