2. Color blindness
Inability or decreased ability to see color,
or perceive color differences, under
normal lighting conditions.
Affects a significant percentage of the
population.
No actual blindness -- deficiency of color
vision
3. • No treatment
• Nor the cause of any significant disability
• No actual blindness -- fault in the
development of one or more sets of retinal
cones that perceive color in light and
transmit that information to the optic
nerve.
• It is a sex-linked condition.
4. • Perception of color begins with specialized
retinal cells containing pigments with
different spectral sensitivities, known as
cone cells.
• In humans, there are three types of cones
sensitive to three different spectra,
resulting in trichromatic color vision.
6. The Genetics
of ColorBlindness
The Retina Contains Two Types of
Light-Detecting Cells
Rods – “See in shades of grey”
– Cannot distinguish different wavelengths
(colors) of light.
– More sensitive to low light
– Used for night-vision
6
7. •
Cones – “See in colors”
– Three types of cones; differ in
which photoreceptor protein
(opsin) they make
• L-cones sense longwavelength (red) light
– Make the long-wavelength
opsin protein
• M-cones sense mediumwavelength (green) light
– Make the mediumwavelength opsin protein
• S-cones sense shortwavelength (blue) light
– Make the short-wavelength
opsin protein
8. Visible light is small part of electromagnetic
spectrum.
IR
UV
700
8
600
500
400
9. Cone cells in the human eye
Cone type
Name
Range
Peak wavelength
S
β
400–500 nm
420–440 nm
M
γ
450–630 nm
534–555 nm
L
ρ
500–700 nm
564–580 nm
12. Color-Vision Genes
• Three kinds of color-vision genes in
humans:
"blue" pigment gene on chromosome 7
"red" and "green" pigment genes at the tip
of the long arm of the X chromosomeXq28
13. Types of Color Vision Deficiencies
By cause
Inherited:
•Trichromacy (“three-color vision”)
– Normal Color Vision
•Anomalous Trichromacy (“unusual three-color vision”)
– See all three primary colors.
– One color is seen weakly
• Protanomaly (L-cone defect) red-weak
• Deuteranomaly (M-cone defect) green-weak, by far the most
common type of color vision deficiency
• Tritanomaly (S-cone defect) blue-weak
13
14. How Color-Blind People See
Things
Normal
Defect in L-cone
(poor red vision)
Defect in M-cone
(poor green vision)
Defect in S-cone
(poor blue vision)
14
15. Dichromacy (“two-color vision”)
– See only two of the three primary colors
– One type of cone is totally absent or nonfunctional
• Protanopia (L-cone absent)
Pure reds cannot be seen, instead appearing black; purple colors cannot be
distinguished from blues; more orange-tinted reds may appear as very dim
yellows
• Deuteranopia (M-cone absent)
moderately affecting red–green hue discrimination
• Tritanopia (S-cone absent)
Blues appear greenish, yellows and oranges appear pinkish, and purple colors
appear deep red
16. A rainbow of colors as
viewed by a person with
no color vision
deficiencies
The same rainbow as
viewed by a person with
protanopia
17. The same rainbow as
viewed by a person with
deuteranopia
The same rainbow as
viewed by a person with
tritanopia
18. Monochromacy, -- "total color blindness", is the lack of
ability to distinguish colors
•Rod Monochromacy (no cones at all) (“no-color vision”)
– Sees no colors, only shades of gray.
•Cone monochromacy is a rare total color blindness
-result of having more than one type of dichromatic color
blindness
21. Acquired Causes
Damage to the eyes, nerves, brain
Some metabolic disorders like
• diabetes
• glaucoma
• macular degeneration
Chronic illness
• Sickle cell anaemia
Exposure to industrial toxins
Drug over dose such as- digoxin, barbiturates, antitubercular drugs
Drug side effects like- Sildenafil (Viagra), Ethambutol,
Chloroquine
22. By Clinical Appearance
Total or partial. Total color blindness is much less common than
partial color blindness.
Partial color blindness
– Red–green
Dichromacy (protanopia and deuteranopia)
Anomalous trichromacy (protanomaly and deuteranomaly)
– Blue–yellow
Dichromacy (tritanopia)
Anomalous trichromacy (tritanomaly)
23. How Color-Blind People See Things
What people with normal
color vision see.
What a red-green color-blind
person sees.
23
24. Congenital color vision deficiency (CVD) is an X
chromosome-linked recessive, autosomal dominant and
very rarely autosomal recessive inherited trait.
Red-Green defects (Protan and Deutan) show the
highest prevalence in the general population.
Impaired color vision, in the case of red-green color
blindness, is genetically determined by X- linked
recessive inheritance and thus occurs in males but is
transmitted via female and about 8.0% of all women are
its carrier.
27. Populations
• Manipur -- small hilly state
• Situated in the north eastern extreme
corner of India.
• Connects the Indian subcontinent to East
Asia and South East Asia as a unique
narrow passageway
28. • Shares an international boundary with
Myanmar (Burma)
• Isolated from the rest of India, both
geographically and economically
30. • Manipuri Muslims -- 8.32% of the total
population -- 2001 census.
• Mostly migrants -- started coming -middle of the 16th century
Muslims
-endogamous
• Manipur
population
31. • Sheikh
• Syed
• Pathan
• Mughal
• Clan names which in Manipuri are called
Yumnak
• About 74 clans are reported in Manipur in
the present times
32. Methods
A cross-sectional, descriptive and analytical study to
detect color-blindness -- Ishihara color test
Individuals belonging to both sexes (Male-1352, Female
-1302) from the area of Imphal East and Imphal west
districts during house to house visit.
Survey was also conducted taking Manipuri students
studying in Aligarh Muslim University, Aligarh.
33. Population groups
Muslims with castes
•Sheikh
•Syed
•Pathan
•Mughal
Hindu (Meitei)
tribal(Naga)
Prior informed consent from the individuals, taking into
consideration the factors like caste, consanguity, age,
religion etc.
34. Color vision deficiency -- 24-plate Ishihara’s Test of Color
Vision
Testing plates -- 75 cm from the person
Tilted at right angle to the line of vision
Done in a properly lighted place
Read the numbers -- test plates 1 to 17
Assessment of the reading of plates 1 to 15 -- normality or
defectiveness of color vision
If 13 or more plates are read correctly, the color vision is
regarded as normal.
If only 9 or less than 9 plates are read correctly, the color
vision was regarded as red green deficient.
The plates 16 and 17 are used to differentiate protan and
deutan types of color vision efficiency.
35. Plate 1
Both normal and those with all
colour vision deficiencies
should read the number 12
36. Plate 2
Those with normal colour vision
should read the number 8.
Those with red-green colour
vision deficiencies should read
the number 3.
Total colour blindness should
not be able to read any numeral.
37. Plate 3
Normal vision should read the number 29.
Red-green deficiencies should read the
number 70.
Total colour blindness should not read any
numeral
38. Plate 4
Normal colour vision should read the number 5.
Red-Green colour deficiencies should read the
number 2.
Total colour blindness should not be able
toread any numeral.
39. Plate 5
Normal colour vision should read the
number 3.
Red-Green deficiencies should read the
number 5.
Total colour blindness should not be able
to read any numeral.
40. Plate 6
Normal colour vision should read the number
15.
Red-Green deficiencies should read the
number 17.
Total colour blindness should not be able to
read any numeral.
41. Plate 7
Normal colour vision should read
the number 74.
Red-Green colour deficiencies
should read the number 21.
Total colour blindness should not
be able to read any numeral.
42. Plate 8
Normal colour vision should read the number
6.
The majority of those with colour vision
deficiencies cannot read this number or will
read it incorrectly.
43. Plate 9
Normal colour vision should read the
number 45.
The majority of those with colour vision
deficiencies cannot read this number or
will read it incorrectly.
44. Plate 10
Normal colour vision should read the number 5.
Those with colour vision deficiencies will not
read the number or read it incorrectly.
45. Plate 11
Normal colour vision should read the
number 7.
Those with colour vision deficiencies
will not read this number or read it
incorrectly.
46. Plate 12
Normal colour vision should read the
number 16.
Those with colour vision deficiencies
will not read this number or read it
incorrectly.
47. Plate 13
Normal colour vision will read the number
73.
Those with colour vision deficiencies should
nor be able to read this number or will read it
incorrectly.
48. Plate 14
Normal colour vision and those with
total colour blindness should not be
able to read any number.
The majority of those with red-green
deficiencies should read the number 5.
49. Plate 15
Normal colour vision and those with
total colour blindness should not be
able to read any number.
The majority of those with red-green
deficiencies should read the number
45.
50. Plate 16
Normal colour vision should read the
number 26.
In protanopia and strong protanomalia the
number 6 is read and in mild protanomalia
both numerals are read but the number 6 is
clearer than the number 2.
In deuteranopia and strong deuteranomalia
only the number 2 is read and in mild
deuteranomalia both the number 2 is clearer
than the number 6.
51. Plate 17
Normal colour vision should read the
number 42.
In protanopia and strong protanomalia the
number 2 is read and in mild protanomalia
both numerals are read but the number 2
is clearer than the number 4.
In deuteranopia and strong
deuteranomalia only the number 4 is read
and in mild deuteranomalia both the
number 4 is clearer than the number 2
.
52. Plate 18
The normal should trace along the
purple and red lines between the two
X's.
In protanopia and strong protanomalia
only the purple line is traced and in
mild protanomalia both lines can be
traced but the purple line is easier to
follow.
In deuteranopia and strong
deuteranomalia only the red line is
traced and in mild deuteranomalia both
lines are traced but the red line is
easier to follow.
53. Plate 19
The majority of those with redgreen colour blindness can trace
the winding line between the two
X's.
The majority of those with normal
and total colour blindness are
unable to follow the line.
54. Plate 20
Normal will trace the blue-green line
between the two X's.
The majority of those with colour vision
deficiencies will be unable to follow the
line or will follow a line different to the
normal one.
55. Plate 21
Normal will trace the orange line
between the two X's.
The majority of those with colour vision
deficiencies will be unable to follow the
line or will follow a line different to the
normal one.
56. Plate 22
Normal should trace the line
connecting the blue-green and
the yellow-green.
Those with red-green
deficiencies trace the line
connecting the blue-green and
purple.
Those with total colour
blindness cannot trace any
line.
57. Plate 23
Normal should trace the line connecting
the purple and the orange between the two
X's.
Red-green deficiencies should trace the
line connecting the purple and the bluegreen.
Total colour blindness and weakness
cannot trace any line.
58. Plate 24
Both normal and those with colour
vision deficiencies can trace the
winding line between the two X's.
59. Genetic Data Analysis
• Phenotypes were recorded for color
blindness for each individual
• Allele frequencies were calculated -Hardy-Weinberg law.
• Level of heterozygosity
Hetrozygosity = 1- ΣHo
Ho -- homozygosity of the allele
60. Results
Face many difficulties in every-day life, some discussed
during the survey include
•Inability to recognize red and green LED displays on
electrical goods
•Difficulties in driving vehicles
Regarding health -- difficulties faced in differentiating
primary colors
•Lack of confidence
•Poor social image i.e. a fear that they are not alike to
normal vision individuals.
61. • Males -- denied the military jobs on grounds of color
blindness have stopped pursuing further studies
• Very few of well educated families have taken this in a
positive way and have started their life in a new way
• General population was mostly unaware of the difficulties
that color blindness can cause; besides they have
neither undergone any screening test
62. • Naga tribes -- least prevalence of color
blindness in both males and females
• Four Muslim caste and the Meitei
population -- higher prevalence of color
blindness.
67. Discussion
• Prevalence of the trait -- muslims is
important -- consanguineous marriages -might result in the birth of children with this
disorder
• The overall percentage of color blindness
-- 5.28%
• higher percentage -- males than in females
• Females -- carriers – 8.37%
68. • Meitei male -- highest color blindness
prevalence rate of 14.93%
• Syed population (11.48%) belonging to
Muslim religion
• Naga population -- the least prevalence
rate of 3.75%
69. • High prevalence rate in Muslims -- higher
frequency of consanguineous marriages
• Meitei population -- highest prevalence
percentage of 8.16% -- large number of
migration by Manipuri people over the past few
years, to different parts of India, indirectly
leading to increase in the rate of exogamous
marriages with non-manipuri populations
70. • Deuteranomaly cases -- higher percentage
• Overall prevalence rate of Protanomaly,
Deuteranomaly, Protanopia, Deuteranopia is
17.14%, 54%, 8.57% and 20% respectively
• Several researchers -- green color receptor is
commonly affected more than red or blue color
receptors
71. Early diagnosis -- beneficial for future family planning and
lifestyles
Helpful to create awareness among the parents and general
public about screening of color vision defects in apparently
healthy children
Nonfatal disorder; usually remain unaware of the defect since
their vision is otherwise normal.
Important for daily life work such as to recognize the traffic
signals during crossing roads or to build career in several
professions like- in Military, Pilot, Driver or Chemist etc.
72. • Congenital color blindness cannot be treated -- non
pathologic, incurable, and remain constant throughout life
• Several therapies have been proposed
Electrical eye stimulation
Iodine injections
Large doses of vitamins
• No treatments or surgical procedures to improve the quality of
an individual’s chromatic vision.
• Optometrists give colored spectacle lenses or a single red-tint
contact lens to be worn over the non-dominant eye. Although
this may improve discrimination of some colors, it can make
other colors more difficult to distinguish.
• X-chrom contact lens
73. • Education, screening and prenatal counseling for the
disease in these areas could help
Minimizing the occurrence of the disorder
Help them to make informed choices and avoid the birth
of children with color blindness
• Moral support from the family and society is required for
the healthy development of mental status of the
individual suffering from this disorder
• Government should also make certain policies and
programmes regarding career choices and jobs for color
blind individuals.