Colour vision , How to check color vision, About colour vision, Types of colour vision , Color vision tests , Theories of colour vision , Characteristics of colour vision , Causes of colour vision , Colour blindness , Defects of colour vision , Optometry , Causes of colour vision , All about color vision , Colour disability , monochromatism , Determine colour deficiency patients ,
2. CONTENT
• What is color vision ?
• Characteristics of color vision.
• Theories of color vision.
• Defects of color vision.
• Clinical test for color vision assessment.
3. WHAT IS COLOUR VISION ?
Colour vision is the ability of the eyes to see and
distinguish between colors based upon their
varying wavelengths in the visible spectrum of light
.
4. CHARACTERISTICS OF COLOUR
VISION
• Hue – Capacity of the eye to discriminate between
the adjacent wavelength . (i.e.. Identification of
colour)
• Brightness – Depends on luminous flux (i.e.
intensity of colour).
• Saturation – It measure the minimum quantity of
given wavelength that must be added to the white
5.
6. THEORIES OF COLOUR VISION
Many theories have been put forward to explain
the properties of human colour vision , but two
have been particularly influential .
I. Trichromatic theory
II. Opponent colour theory
7. TRICHROMATIC THEORY
• It was originally suggested by Young and
subsequently modified by Helmholtz . Hence it is
called Young – Helmholtz theory .
• It postulates the existence of three kinds of cone,
each contains a different photopigment and
maximally sensitive to one of three primary
colours that are red , green and blue.
8. • Red Sensitive Cone Pigment also known as
erythrolabe or long wavelength sensitive (LWS),
absorbs maximally in a yellow position with a
peak at 565nm.
• Green Sensitive Cone Pigment also known as
chlorolabe or medium wavelength (MWS) cone
pigment, absorbs maximally in the green portion
with a peak at 535nm.
• Blue Sensitive Cone Pigment also known as
cyanolabe or short wavelength (SWS) cone
9. OPPONENT COLOUR THEORY
• The opponent colour theory of Hering points out
that some colours appear to be “mutually
exclusive”.
• There is no such colour as “reddish green” and
such phenomenon can be difficult to explain on
the basis of Trichromatic theory alone.
10. COLOUR BLINDNESS
• Insensitive to light i.e. inability on the part of an
individual to recognize the colours is called
colour blindness .
• An individual with normal colour vision is known
as trichromat.
• The ability to appreciate one or more primary
colour is either defective (anomalous) or absent
(anopia).
11.
12. • Congenital :
• Dyschromatopsia – It means color confusion due
to deficiency of mechanism to perceive color .
• Anomalous trichromatism – Here the mechanism
to appreciate all the three primary colour is
present but is defective for one or two of them .
• Protanomaly – It refers to defective red color
appreciation .
• Deuteranomaly – It refers to defective green color
appreciation .
13. • Tritanomaly – It refers to defective blue colour
appreciation .
• Dichromatism – In this condition , the ability to
perceive one of the three primary colour is
completely absent .
• Protanopia – unable to receive red colour.
• Deuteranopia – unable to receive green colour.
• Tritanopia – unable to receive blue colour.
14. • Achromatopsia – It is an extremely rare condition
, where the patient will see only one colour or
shades of that colour.
• Cone monochromatism – Only one primary colour
is present and have visual acuity of 6/12 or
better.
• Rod monochromatism – In this , the person is
totally colour blind and sees everything in shades
of grey.
15. • Acquired colour blindness :
• Type 1 – Red-Green deficiency : It is seen in optic
nerve lesions such as optic neuritis (inflammation
of the optic nerve ) , Leber’s optic atrophy (It is a
mitochondrial disorder , hereditary disorder ,
main symptom blurriness of the central vision ,
affects young males ) , compression of the optic
nerve.
16. • Type 2 – Red-Green deficiency : It is seen in
progressive cone dystrophies (functional disorder
, functionally abnormal), retinal pigment
epithelium dystrophies.
• Type 3 – Blue-Yellow deficiency : It is seen in
retinal lesions such as macular edema (swelling of
the macula)
17. CLINICAL TEST FOR COLOUR
VISION ASSESSMENT
1. Pseudoisochromatic test
a. Ishihara colour vision chart
b. AOHRR – American Optical Hardy Rand Rittle
Plate
2. Arrangement test
a. Fransworth Munsell – 100 Hue test
b. Fransworth D–15 test
19. ISHIHARA COLOUR VISION CHART
• It is based on the colour confusion .
• Available in 17 , 25 and 38 plates .
• Each plate known as pseudoisochromatic plate is
crowded with coloured spots .
• It is used to determine red – green deficiency .
20. 1. Demonstration plate (1)
a. Number written on the plate is 12
b. Both normal and colour vision defect patient can
read.
2. Transformation plate (2-9)
a. Numbers written on the plates are 8, 6, 29, 57, 5, 3,
15 and 74.
b. Normal person will read correctly.
c. Red – green deficiency person can read them as 3,
5, 70, 35, 2, 5, 17 and 21.
22. 3. Vanishing plate(10-17)
• Number written on the plates are 2,6,97,45,5,
7,16, 73.
• Normal people will read them correctly.
• Red-green deficiency person will not be able to
read.
• Total color vision defect can’t read any number.
4. Hidden plate (18-21)
• The numbers written on the plates are 5, 2, 45,
73 .
• Normal and total color defect person will not be
24. 5. Diagnostic plate (22-25)
• The numbers written on the plate are 26, 42, 35,
96 .
• Normal person will read correctly .
• Strong protanomaly and protanopia read only 6,
2, 5, 6 .
• For mild protanomaly 6, 2, 5, and 6 are clearer
than other.
• Strong deuteranomaly and deuteranopia read only
2, 4, 3 and 9
26. 6. Tracing plate (26-38)
• It contains pathways .
• It is used for illiterate and children.
27. ANALYSIS OF RESULT FOR
ISHIHARA CHART
• NORMAL – if 17 or more plate are read correctly .
• COLOR VISION DEFECT – if 13 or less than 13
plates are read .
• REPEAT TEST – if between 13 to 17 plates are read
.
28. METHOD FOR ISHIHARA COLOR
VISION TEST
1. The room should have good illumination as day
light.
2. Patient should wear appropriate spectacle
correction and occlude one eye.
3. The test plate is held at a distance of 75 cm.
4. Ask the patient to read the plates.
5. For illiterate patient ask to trace the line
29. AOHRR(American Optical Hardy,
Rand, Rittler Plates )
• American Optical Hardy, Rand, Rittler (H-R-R)
plates are another type of pseudoisochromatic
plate test. This test is similar to the Ishihara test
except that the H-R-R plates classify and quantify
the type of colour defect whether protan, deutran
or tritan.
30. • H-R-R plates have coloured symbols/shapes
rather than numbers.
• H-R-R plates is a good choice for children and
illiterates.
• Lighting, viewing distance, and viewing time are
the same as that of testing with Ishihara plates.
32. Farnsworth-Munsell 100- Hue
Test (Pigment Matching Test)
• Farnsworth-Munsell test is a psycho-technical
test, which quantifies a person's ability to
discriminate hues of pigment colour.
• This test consists of 85 coloured chips that are
designed to approximate the minimum difference
between the hues that a normal observer can
distinguish.
33. • Color deficient persons make characteristic errors
in arranging the chips.
• The results are recorded on a circular graph.
• The greater the error arranging the
chips, the farther the score is plotted
from the centre of the circle.
34. Farnsworth D-15 Test
• The Farnsworth D-15 test consists of single box
of 15 coloured chips and a reference cap that is
fixed. The test can be carried out more rapidly
than the 100-hue test.
• Viewing distance required is 50 cm.
• Unlimited testing time is usually allowed but the
subject may be told he/she has two minutes to
complete the test in order to prevent wasting of
time .
35. • Main purpose of this test is to divide the patient
into one of the two groups , those with mild or no
deficiencies and those with moderate to severe
deficiencies .
• The object of the test is to arrange the caps in
order using the fixed reference cap as a starting
point.
• First let the patient see the correct sequence and
then we have to take the chips out of the box ,
mix them up and place it Infront of the patient .
36. • The patient is instructed to take the cap which
most closely resembles the fixed reference cap,
and place it next to it; then find the cap that most
closely resembles the cap he just placed, and
place it next to it.
• Once the subject has arranged all the caps, the lid
is closed and the box flipped over and scoring is
done on the scoring card.
37. Nagel Anomaloscope
(Spectral Matching Test)
• Nagel (1970) contructed anomaloscope for
studying the colour vision defects.
• It is based on the colour match known as the
Rayleigh equation, that is Red (R) +Green(G) =
Yellow(Y).
39. • In anomaloscope, the observer is asked to match
a mixture of red and green wavelengths to a
yellow.The instrument consists of a source of
white light, which is split into spectral colours by
a prism. These colours are viewed through a
telescope. The filed of vision consists of a circle
divided into two halves.
• The lower half projects a spectral Yellow (Sodium
line) and this has to be matched by a mixture of
Red (Lithium line) and Green(Thallium line) in the
