Assessment of Inherited Colour Vision Defects

Assessment of Inherited Colour
Vision Defects in Clinical Practice
Yasmine; Maram; Kholoud; Rami30/03/2013
1

contents
 The purpose of the discussion
 Introduction to CVD.
 Diagnostic tests for CVD.
 Management
 Advices to patients
 Special Occupations and CVD
 Short glossary
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Maram Hajir

Purposes
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To recommend tests for primary
care assessment of colour vision
To Learn you about the methods
and analysis for tests
To give you an info. About
Management for CVD
To provide guidance on the advice
that can be given to patients with
CVD
Maram Hajir

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 The retina of the human eye contains about 7
million cone cells
 and more than 100 million rod cells that enable
normal vision.

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 Color is light, which is carried as specific
wavelengths that the eye absorbs and the brain
converts into messages so that we ‘see colors.

Colour Vision Deficiency ( CVD )
 Colour vision deficiency (CVD) is the
inability to distinguish certain shades of color or in
more severe cases, see colours at all.
 It is a common functional disorder of vision.
 Prevalence of CVD among Caucasian population is
reported as 8% on males and 0.4% on females
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Maram Hajir

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The mood of inheritance
Maram Hajir

Classifications of CVD
-Typical Monochromasy( rare)
-Blue cone Monochromasy ( rare)
-Protanopia (1% of men 0.01% women)
-Deuteranopia (1% of men 0.01% women)
-Tritanopia (1 in 13,000 both men & women equally)
-Protanomaly (1% of men 0.03% women)
-Deuteranomaly (5% of men 0.35% women)
-Tritanomaly (rare)
Monochromasy
Dichromasy
Anomalous
trichromasy
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Maram Hajir

MonochromasyTypicalMonochromasy
(rare)
 mechanism
 mutation of genes encoding the cone-specific alpha
and beta sub-units of the cation channel
 Characteristics
 Colour blind. No perception of colours. Colours
distinguished by brightness differences only. Very
insensitive to red light.
 Nystagmus.
 Low visual acuity 6/36 to 6/60
 Painless photophobia.
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Maram Hajir

Cont.
Blueconemonochromasy
 mechanism
 S (blue) cone pigment only.
 Characteristics
 Colour blind. Colours distinguished by brightness
differences only.
 Rudimentary colour vision in mesopic vision from rod
and blue cone activation.
 Very insensitive to red light.
 Nystagmus.
 Low visual acuity 6/12 to 6/24.
 Painless photophobia.
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Maram Hajir

Dichromasy
Protanopia(1%ofmen0.01%women)
 mechanism
 Absence of L (red) cone pigment.
 Characteristics
 Very reduced ability to identify colours.
 Confuse red, yellow and green, white and green, and
blue and purple.
 Reduced sensitivity to red light.
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Maram Hajir

Cont.
Deuteranopia(1%ofmen0.01%women)
 Mechanism
 Absence of M (green) cone pigment.
 Characteristics
 Confuse red, yellow and green, and white and green.
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Maram Hajir

Cont.
Tritanopia(1in13,000bothme&
womenequally)
 mechanism
 Absence of S (blue) cone pigment.
 Characteristics
 Confuse blue with blue green and green, and white
with yellow.
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Maram Hajir

Anomalous trichromasy
Protanomaly(1%ofmen0.03%women)
 mechanism
 L (Red) cone pigment absorption spectrum shifted to
shorter wavelengths of light
 Characteristics
 May confuse white with green and confuse reds,
yellows and greens but loss of colour discrimination
varies greatly between individuals.
 Reduced sensitivity to red light.
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Maram Hajir

Cont.
Deuteranomaly(5%ofmen0.35%
women)
 mechanism
 M (Green) cone pigment absorption spectrum shifted
to longer wavelengths of light.
 Characteristics
 May confuse white with green and confuse reds,
yellows and greens but loss of colour discrimination
varies greatly between individuals.
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Maram Hajir

Cont.
Tritanomaly(rare)
 mechanism
 Partial loss of S cone pigment.
 Characteristics
 Loss of colour discrimination for blues, blue-greens,
and greens.
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Maram Hajir

Tests that used in CVD detection
CVD
Jasmine R. AbdulRahman
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Types of tests
Ishihara test
Farnsworth Panel D‐15
Farnsworth‐ Munsell 100‐hue
Medmont C100 test
Richmond HRR test (2002)
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Isochromatic Vs Pseudoisochromatic!
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 Pseudoisochromatic plates frequently are used by
eye specialists to get an idea of one’s color
efficiency or deficiency. i.e.:
 The Ishihara color test
 Richmond HRR 2002
 SPP2
 Dvorine

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 “isochromatic”: To a color-deficient person,
all the dots in one or more of the plates will appear
similar or the same.
 “Pseudoisochromatic” : To a person without
a color deficiency, some of the dots will appear
dissimilar enough from the other dots to form a
distinct figure (number) on each of the plates

Ishihara test
 It was created by Dr. Shinobu
Ishihara (1879‐1963).
 designed to detect congenital
color deficiencies.
 Ishihara contains 38 plates.
 Pseudoisochromatic plates
History Ishihara plates
http://www.guldenophthalmics.com/ccp7/media/ecom/prodl
g/Ishihara-Color-Test-Book.jpg
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Capability
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 Detects protan and deutan CVD with high sensitivity
and specificity.
Screening Congenital Acquired Ability to
classify
No. of plates
Yes Yes No No 38

Methods
 Dr. Liana, Please chose one paper from this box :D
 Please read the name that you select.
 Please …. If you don’t mind, the test will be done on
you.
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Methods
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 lit adequately by daylight or under electric light
 Electric light should be as far as possible to resemble the effect of the natural
daylight
 The plates are held 75 cm from the subject and tilted
 the plane of the paper is at right angles to the line of vision
 each answer should be given without more than three seconds delay.
 If the subject is unable to read numerals, plates 26-38 are used and the
winding lines between the two X’s are traced with the brush. Each
tracing should be completed within ten seconds

Methods
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 In a large scale examination the test may be
simplified to an examination of six plates only
1. No 1
2. one of the Numbers 2, 3, 4, 5
3. one of Numbers 6, 7, 8, 9
4. one of Numbers 10,11, 12, 13
5. one of Numbers 14, 15, 16, 17
6. one of Numbers 18,19,20,21.
 It may be necessary to vary the order of the plates if it is
suspected that there is a deliberate deception on the part
of the subject.

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Word Document

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Plate number How normal read How red-green Deficiencies read How total blind
read
No. 1 12 12 12
No. 2 8 3 X
No. 4 29 70 X
No. 6 5 2 X
No. 7 3 5 X
No. 8 15 17 X
No. 9 74 21 X
No.11 6 X or read incorrectly X
No. 13 45 X or read incorrectly X
No. 18 X 5 X
No. 20 X 45 X
Strong
protan
Mild Protan Strong
Deutan
Mild Deutan
No.22 26 6 2 & 6 (6 clearer) 2 2 & 6 (2 clearer)
No. 23 42 2 4 & 2 (2 clearer) 4 4 & 2 (4 clearer)

How to interpret results
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 Scoring occurs on the first 21 plates
 17/21 or more is considered normal
 13/21 or less is abnormal.

Interpretation
 Errors on three or more of the numeral plates indicates red-
green CVD with a small chance (2%) of misdiagnosing
normal colour vision.
 Five or more errors indicates certain red-green CVD.
 Number of errors is not a useful measure of severity.
 Subjects making very few errors will probably have a mild defect
but those who make a large number of errors may be mild or severe.
 Failure to see the red numeral indicates protan.
 failure to see the red-purple numeral indicates deutan.
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Care of the book
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 Book of the test plates should be kept closed.
 Except during use :P
 Exposure to sunlight causes a faiding of the color of
the plates.
 Use sterile cotton swap in tracing plates.
 Don’t touch the plate.

Farnsworth Panel D‐15
 designed by Dean
Farnsworth
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History Farnsworth Panel D‐15
http://www.e-mfp.org/Assets/Farnsworth_Panel1.jpg
Kholoud Abu Abdoun

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 most widely used of the colour sorting tests and
must be part of primary care colour vision
assessment.
Kholoud Abo Abdoun
Screening Congenital Acquired Ability to
classify
No. of plates Time to
Administer
Yes Yes Yes Yes 16 chips Slow

Purposes
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 To reveal the color blindness
 To differentiate among subjects affected with
 Dyschromatopsia ( little affected abnormal
trichromatic) from those who are
 Severely affected ( dichromatic)
Kholoud Abo Abdoun

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Description of the test
Cautions
 It is recommended:
 Not to expose the caps to light.
 To avoid touching the colors with fingers.
 To avoid damage the caps and their colors
Kholoud Abo Abdoun

Methods
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 Either on Daylight or on front of a wide window
and under a clear sky.
 The position for examiner and patient is a cross the
table.
 The caps numbered from 1-15 are arranged in
random order.
 The subject educated to choose the cap after cap
and arrange them on the case based on the color
degree as he/she see.
 patient start from the reference cap P.
Kholoud Abo Abdoun

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 To eliminate the waste time, examiner told the
patient that the test take only 1-2 minutes to finish.
 anyway examiner let the patient to finish normally.
 Those who finished quickly, ask him to check their
classifications.
 The case is closed and turned over; it is now ready
for future testing.
 Starting from the reference cap, the points of
diagram are connected according to the order
presented by the subject.
Kholoud Abo Abdoun

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Kholoud Abo Abdoun

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Kholoud Abo Abdoun

Interpretation
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 The results of the test can be either a:
 ”success” circular diagram.
 or “failure” diagram with parallel lines
http://webvision.med.utah.edu/imageswv/KallColor25.jpg

The diagrams of subject
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 Either normal or slightly deficient follow the circle.
 For color blind subject the diagrams from parallel
or crisscrossed lines (with at least two parallel lines
crossing the diagram)
 Note: test should be repeated in the event of a
doubtful interpretation.
Kholoud Abo Abdoun

some cases of success and failure
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 Example of success: normal and slightly deficient results. The subjects
with normal vision place the caps in a perfect order or in interchanging one
or two caps .
 Example of failure: results of color blind subjects.
 Fig. 4 shows the diagram of a red blind patient (dichromatich). The lines f
diagram are parallel to the protan axis.
 Fig. 6 shows the diagram of a subject blind to blue or purple with lines
parallel to the tritan axis.
 There is a very uncommon case of complete color blindness: the patient
will be totally unable to place the caps in a logical order.
Kholoud Abo Abdoun

Richmond HRR
 The HRR
pseudoisochromatic
test was developed by
Hardy, Rand and
Rittler.and it is
supports very
efficient color
defeciency screening
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History
Maram Hajir

Capability
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1. Detects protan and deutan CVD with a sensitivity
and specificity only slightly less than that of the
Ishihara test.
2. Ideal confirmation test for the Ishihara test.
3. Detects tritan defects
4. May differentiate protan, deutan and tritan
defects.
5. Classifies severity as mild, medium and strong.

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 It serves as a confirmation of the result of the
Ishihara test and can guard against the possibility
that the patient has learned the correct answers for
the Ishihara. It has a sensitivity and specificity
almost as good as the Ishihara. It can also detect
tritan defects, which the Ishihara does not.
Maram Hajir

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 This might be thought to be of little importance as
inherited tritan defects are rare, having a prevalence
of only 1 in 13,00021 and blue and yellow are not
as important in colour codes as are red, green and
yellow, however, tritans can encounter occupational
colour problems.
Maram Hajir

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 So do u think that HRR can detect the aquired CVD
?
Maram Hajir

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 Yes , by popular configuration of the HRR , called
the HRR Combo and provides the full 24 plates
laminated with plastic to protect them against the
acid in fingerprints. The Combo also provides a full
set of Amsler Grids. Amsler testing completes the
prescribed regimen for acquired color testing
Maram Hajir

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 The last advantage of the HRR test is that it can be
used with very young children because it uses
symbols, a circle, a triangle and a cross, which can
often be named or traced by young children before
they can read numbers.
Maram Hajir

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 Alternatively, key cards can be made so children
can identify the symbols they see.
Maram Hajir

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Richmond HRR (24 plates )
first 4 plates
to show how
the test work
the fourth
plate has no
figure
4 plates for
R/G
screening
contain 6
symbols
2 plates for
tritan
screening
contain 4
sbmbols
14 plate for
extent
10 for R/G
4 for blue
CVD
Maram Hajir

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 Two or more errors with the six symbols on the four red-green screening
plates indicates abnormal colour vision but a few patients (4%) with
normal colour vision will make two errors.
 Three or more errors indicates certain red-green CVD. The majority (98%)
of those with a red/green defect make three or more errors on the screening
plates.
 No data on detection of tritan defects with the Richmond HRR 2002 test
but the screening plates of the original AO HRR test have been shown to
detect tritan defects, but not all.

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 If no errors are made on the four symbols on the two tritan screening plates ask
if one of each pair of symbols in the tritan screening and classification plates is
much fainter than the other. If the tritan symbols look fainter, a tritan defect is
probable.
 Correct classification as protan or deutan on 86% of occasions, 3% wrongly
classified, remainder ambiguous. Tritan defects clearly differentiated if
detected.
 Errors in first five classification plates indicates mild CVD (30% CVDs).
Errors on next three classification plates = medium CVD (45% CVDs) Errors
on last two classification plates = strong CVD (25% CVDs). However,
meaning of ‘medium’ and ‘severe’ is uncertain as some mild CVD are
classified ‘medium’ or ‘strong’ and dichromats may be classified as ‘medium’.

Medmont C100 test
 The Medmont C-100 owes it
origin to Estvez and
colleagues.
 who thought of applying the
principle of flicker
photometry to the assessment
of colour vision.
 The first commercially
available instrument using
this principle was the
OSCAR, produced by a
Dutch company Medilog
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History Medmont C100 test
http://www.medmont.com.au/medi
a/2722/c100_top.jpg

Overview
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 The Medmont C-100 test is not well known but it
must be a part of the basic battery of colour vision
tests.
 It has only one function, which is to differentiate
protans and deutans among those who have red-
green abnormal colour vision

Overview
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 objective screening of colour anomalies and
reductions.
 It is an inexpensive test and takes only a minute or
two to administer.

Features
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1. Rapid colour deficiency indication
2. Unique, easy to read scale (graphic colour bar indicator)
3. Portable, with mains operated power pack (no batteries)
4. 3 Years Warranty
5. Comes with protective case, plug-in mains power pack and User
Guide.
6. Dimensions (mm): 70W x 35H x 113L

Procedure
1. Normal room light
conditions are suitable but
any fluorescent lights which
exhibit noticeable flicker
should be switched off.
2. The subject was asked to
hold the instrument at a
distance of about 40 cm,
and look at the small
circular flickering disk.  http://www.medmont.com.au/p
roducts/c100-colour-vision-
tester.aspx
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Steps Medmont C100

Procedure
3. The subject was instructed
to adjust the control knob
located on the top of the
Medmont C100 case
4. Then the subject would
adjust the knob slowly to a
point where the light flicker
disappears or is a minimum.
 http://www.medmont.com.au/produc
ts/c100-colour-vision-tester.aspx
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Steps Medmont C100

Recommendations
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 The experimenter records the readings as shown on
the indicator at the rear of the instrument.
 It is recommended that the patient be given two
practice attempts at obtaining a minimum flicker
point, and the measurements should be repeated at
least four times for statistical averaging.

Results Analysis
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 The settings chosen to achieve no or minimum
flicker are read on an arbitrary scale from -5 to
+ 5.
 +2.0 to -2.0 is the extreme range of normal
settings
 but typically settings are within ± 1.0
 The scale is colour-coded red for protan
settings, green for deutan and yellow for
normal
 The colour-coded scale lights correspond to
integers (1, 2, 3 ...)
 but can be interpolated to 0.5, when two
adjoining lights are illuminated.

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 If two adjacent LEDs are equally illuminated, the
reading would be halfway between the two LED
values.
 if the two yellow LEDs are equally illuminated, the
reading would be zero.
 Similarly, if a yellow LED and its adjacent green LED
are equally illuminated, the reading would be 1.5

Results
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 The Medmont C-100 can also diagnose women
who have normal colour vision but are carriers of
the abnormal gene for protanomaly or protanopia.
 The Medmont C-100 colour vision test measures
relative spectral sensitivity using flicker photometry
to differentiate protans and deutans. It should be able
to diagnose Schmidt's sign.

Fransworth‐ Munsell 100‐hue
 designed by Dean
Farnsworth
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History
Rami Danaa
http://www.utsl.co.th/upload/product/Munsell%2
0Color%20FM%20100%20Hue%20Test.jpg

Fransworth‐ Munsell 100‐HUE
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Purpose
Divide persons with normal CV
into classes of superior, average
and low color discrimination
Determining the type and
severity of CVD
Rami Danaa

Fransworth‐ Munsell 100‐HUE
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Components
Four wooden cases
Lighting
Administrator-to-
patient Position
Scoring sheet
Rami Danaa

Procedure
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Rami Danaa

Procedure
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Rami Danaa

Indications of Re-testing
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Rami Danaa

Interpretation
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• About 68% of the population wit normal
CV has average color discrimination
• The pattern will be characterized by TEC
ranges from 20 to 100
Average
discrimination
CV has superior color discrimination
ranges from zero to 16
superior
discrimination
CV has low color discrimination
more than 100
Low
discrimination
Rami Danaa

Interpretation
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Rami Danaa

Interpretation
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• The mid point is located
between 62 and 70Protans
between 56 and 61Duetans
between 46 to 52Triatns
Rami Danaa

Interpretation
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Rami Danaa

Limitation
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 The major limitation of the test is the long time
required to perform the test and to analyze the
results.
Rami Danaa

To avoid waste time see the video
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Video

Why color vision test is not always done in
routine clinical practice?
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1. there is no single test of colour vision that
provides the clinician with all the information
needed to advise patients.
2. proper assessment of abnormal colour vision
needs several tests, which takes time, and the
clinician has to decide which supplementary
colour vision tests should be used.
Rami Danaa

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3. there is no treatment for abnormal colour vision so
there may seem little point in diagnosing it.
4. the classification of CVDs is complex and may
not be easily remembered by practitioners who do
not routinely diagnose abnormal colour vision
with an anomaloscope.
Rami Danaa

Treatment, „Compensation‟ & Cure
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• Some CVD sufferers can be helped by
color filters which act to increase the
contrast and reportedly make it possible to
distinguish colors close to the confusion
lines
• Some people benefit from the use of an X-
Chrom lens which is available as a contact
lens. Again, these filters may serve to
increase color contrast. Further, spectacles
that reduce glare may also help congenital
CVD sufferers.
‘THERAPEUTIC’
METHODS
• In 2009 the Departments of Ophthalmology
at the University of Washington in Seattle,
the University of Florida in Gainsville and
the Medical College of Wisconsin in
Milwaukee published the results of a
research program aimed at correcting the
red-green vision of squirrel monkeys with
congenital (dichromatic) CVD using gene
therapy. It was shown that after applying
gene therapy the monkeys were able to
distinguish between patterns of gray, green
and red dots.
GENE THERAPY
RESEARCH IN
PRIMATES
Rami Danaa

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 In the absence of the development of a cure for
congenital CVD, safety remains a key issue. Those
with a strong or medium level of congenital CVD
need to avoid activities where color confusion may
jeopardize others.
Rami Danaa

Advice to Patients
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 The difficulties of giving advice
 There is always great potential for misunderstanding
and misremembering.
 It should not be assumed that the patient who learns of
his abnormal colour vision for the first time will
receive the news with interest or gratitude
Rami Danaa

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 Steward and Cole report that of the 18 patients in their survey who were
previously unaware of their abnormal colour vision, half expressed
disbelief and denied they had any problem with colour and half were
accepting and acknowledged that on reflection they did have problems
with colour.
 Pickford and Cobb found 44 per cent of a sample of 36 subjects diagnosed
to have CVD for the first time exhibited denial, which they define as ‘a
wide range of attitudes from plain disbelief in the tests to an unwillingness
to agree that the defect, if it does exist, would have any influence on their
daily life’. Only 22 per cent of the sample demonstrated a coping attitude,
that is, acceptance of the defect and an effort to adapt. The rest of the
sample exhibited some form of overcompensation about their defect
Rami Danaa

Career advice
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 Some occupations have a statutory colour vision requirement
but these vary between countries and between states within
countries and are often poorly defined and administered.
 There are also several occupations, for which there is no
statutory colour vision requirement but for which abnormal
colour vision is a handicap.
 it is not possible to provide a comprehensive list and full
details of all occupational colour vision standards
Kholoud Abo Abdoun

Occupational colour requirements broad
categories
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1. Normal colour vision
2. Defective colour vision that is sufficiently mild
to enable the colour task to be performed
Kholoud Abo Abdoun

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Normalcolour
vision Normal colour vision is required for occupations that involve
precise colour matching
Also for occupations for which it is deemed that recognition
of signal lights and other colour codes is absolutely critical
to safety
Examples: deck officers and seamen, train drivers, air traffic
controllers
(in Australia) and some occupations in the defence forces
All patients with CVD, however mild, can be told that it is
very likely that these careers will not be open to them.
Kholoud Abo Abdoun

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Defectivecolour
vision that is sufficiently mild to enable the colour
task to be performed
The two most common occupational colour tasks
that give rise to an occupational colour vision
standard are the recognition of signal lights and
surface colour codes
Lantern test for recognition of signal lights
Farnsworth D15 test for surface colour codes
Kholoud Abo Abdoun

Lantern
 The present instrument was
developed when the College and
the Association of Optometrists
jointly organised a competition
to meet the need for a new
lantern design for certain British
Aviation & Marine colour vision
tests. In 2002 the CAM
prototype lantern designed by
Prof. R. Fletcher won the
competition.
 The Fletcher CAM
Lantern
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History
Kholoud Abo Abdoun

Overview
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 Lanterns are valuable practical ways of detecting colour vision
defects, having been used in clinical, aviation and marine
assessments for many years.
 Lantern tests can instil confidence perhaps lacking with other
conventional tests.
 The task of naming small coloured lights resembles practical signals
& transport situations
 This is valuable in Optometric and Ophthalmological practice for
inherited and acquired colour vision defects.
Kholoud Abo Abdoun

Typical Uses
1. tests for aircraft pilots, mariners, railway drivers
and other occupations.
2. assessment of inherited anomalies of colour
perception (about 5 – 8 % of the male
population).
3. detection of visual changes sometimes caused by
diabetes, cataract, retinal degeneration, etc
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Kholoud Abo Abdoun

Methods
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 Naming the colours, at 6 metres reflected in a
standard mirror, is the essential task.
 Aviation and Clinical tests These are presented in
a quiet room with illumination between 80 and 200
lux.
 Two manual knobs at the back control the
Aperture sequence & the Colour sequence.
 A shutter exposes the coloured lights for 2
seconds, & subjects should respond within 5
seconds.
Kholoud Abo Abdoun

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Kholoud Abo Abdoun

How Can Color Deficiencies Limit
Humans?
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 Careers
 Bus Driver, Firefighters, Police Officers, Paint Makers,
Doctors, Chemists, Decorators, Computer Programmers
 School
 Affects Reading and Math Skills

Traffic signs
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Normal Deuteranopes protanopes
relying on brightness or location, rather than color, to identify objects or situations
can help.
For example, by learning the order of the three colored lights on a traffic signal and
knowing that if the lowermost light is illuminated, it means that the light is green

Telecommunications and electrical
cables.
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 They will recognise the blue and white cables but will be uncertain about the
red, orange, brown and green.

Colour indicates how well meat is
cooked?
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 lack of perception of red makes it hard for them to identify
the uncooked piece of meat.

Colour indicates ripeness of fruit
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 Nearly 30 per cent of people with abnormal colour vision
report they have trouble judging the ripeness of fruit.

diagnosis of illness!!
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 Medical practitioners and optometrists who have abnormal colour vision
often report that they have trouble seeing redness of inflammation.
 18% of those with abnormal colour vision report that they have difficulty
seeing skin rashes, sunburn and blushing.

Colour is often used to distinguish an object from
others that are similar
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 This is especially the case in police work, where colour is often
used to describe suspects, evidence and motor cars.
 They will be able to identify the yellow car and the blue, white and
silver cars but not the red and green cars. Note that the
illuminated brake lights in the red car in the second row of parked
cars are not evident in the dichromatic transformations.

Denotative use of colour
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 Colour is often used as an identifier at school.
 An instruction to colour a drawing in a certain colour can be
bewildering for the colour vision deficient school child
 Parents should write the names of the colours on the pencils.

Colour in search
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 Colour often marks out objects and facilitates
search for them.

Colour and search
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 Colour coding in maps is used to code the class of feature.
 to mark out and differentiate for example, blue for district
names and route numbers.

Short Glossary
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Maram Hajir

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 Achromatism/Achromatopsia
 Rare inability to distinguish colors. See also Monochromacy.
 Cone
 Light-sensitive retinal receptor cell that provides sharp visual acuity and
color discrimination. See also Rod.
 Deutan
 Refers to a person who has deuteranopia, a type of dichromatism in
which red and green are confused. Also deteranomaly, a type of
anomalous trichromatism in which an abnormally high proportion of
the green is needed when mixing red and green to produce yellow.
 Dichromatism
 Moderately severe color vision defect in which one of the three basic
color mechanisms is absent or not functioning.
Maram Hajir

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 Protan
 Refers to a person who has protanopia, a type of dichromatism in which
only two hues are seen. Also protanomaly, a type of anomalous
trichromatism in which an abnormally high proportion of the red
primary stimulus is needed when mixing red and green to produce
yellow.
 Dyschromatopsia
 Any type or degree of defective color vision.
 HRR
 Hardy-Rand-Rittler pseudoisochromatic plate test of colored dots that
appear as recognizable geometric shapes. Used for identifying color
vision deficiencies.
 Ishihara
 Pseudoisochromatic plate test similar to the HRR test, but with certain
limitations.
Maram Hajir

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 Monochromacy/ Achromatism/Achromatopsia
 Rare inability to distinguish colors
 Munsell Scale
 Standardized scale of colored materials having
variations in hue and saturation.
 Tetartan
 Refers to a person with tetartanopia or tetartanopsia,
theoretical conditions and terms for a type of blue-
yellow blindness in which there are two neutral points.
Maram Hajir

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 Trichromatic
 Requiring the use of three color mixture primaries to match all
perceived hues. Anomalous trichromatic is a form of defective
color vision in which three primary colors are also required for
color matching, but the proportion of primaries in the
mixturematches are significantly different from those required in
normal trichromatism.
 Tritan
 Refers to a person having tritanomaly or tritanopia. The former is
a rare type of defective color vision in which an abnormally large
proportion of blue must be mixed with green to match a standard
blue-green stimulus. Tritanopia is a form of dichromatism in
which all colors can be matched by suitable mixtures of only a
red primary and a green or blue primary.
Maram Hajir

References
 Michael N. Wiggins, MD. How we should really be doing and interpreting the Ishihara. Retrieved by
March 16,2013 from www.jomtonline.com/jomt/articles/volumes/5/2/HowWeIshihara.pdf
 Alotaibi Z.A et.al. Assessment of the Medmont C100 test for colour vision screening of male Saudi
Arabians. S Afr Optom 2011 70(1) 14-20
 Ross W Harris & Barry L Cole. Diagnosing protan heterozygosity using the Medmont C-100 colour
vision test. Clin Exp Optom 2005; 88: 4: 240–247
 Cole B.L, Lian K.L & Lakkis C. The new Richmon HRR Pseudoisochromatic test for color vision is better
that ishihara test. Clin Exp Optom 2006; 89: 2: 73–80
 Maciej Laskowski. USING CUSTOMIZED PSEUDOISOCHROMATIC PLATES FOR
DETECTING CHOSEN FORMS OF DICHROMACY. Journal of KONES Powertrain and Transport,
Vol. 19, No. 1 2012
 SHINOBU ISHIHARA. Ishihara Instructions. Retrieved by March 16,2013 from
white.stanford.edu/newlm/.../Ishihara.14.Plate.Instructions.pdf
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