Color vision : introduction, classification, causes

for optometry students

1. Anantapoudel
B.Optom1
st
batch NAMS

2. Presentation layout.
Introduction on color vision
Introduction on color blindness.
Types of colourvision defect and its classification, causes.
Prevalence.
Congenital vsacquired colourvision defect.

3. Introduction on color vision
Color vision is that attribute of the sense of sight
which provides an appreciation of differences in the
physical composition of wavelength of light that excite
the retina.
John daltonfirst reported color vision in 1798 (reports
of his own color blindness as compared to his
colleagues with normal color vision.

4. Colourvision is a function of the cones and thus,
better appreciated in photopicvision.
In dim light (scotopicvision), all colors are seen grey
and this phenomenon is called Purkinje shift.

5. There are three different types of cones viz.
redsensitive, 56%(erythrolabe)
greensensitive, 37% (chlorolabe)
bluesensitive, 7% (cynolabe)
which combinedlyperform the function of colour
vision

7. Facts.
Color perceptions best in the fovea and declines in the
periphery.
The "green" and "red" cones are mostly packed into
thefovea centralis.
Sensitivity to red–green color variations declines more
steeply toward the periphery than sensitivity to luminance
or blue–yellow colors. Due to the increasing size of
receptive fields of parvocellularretinal ganglion cells
ref.ARVO journal

8. •Illustration of the distribution of cone cells in thefoveaof an
individual with normal color vision (left), and a color blind
(protanopic) retina. The center of the fovea holds very few blue
sensitive cones.

9. Colourshave three attributes :
(1)Hue:Definedashowmostofusperceiveandname
acolor–usingthecolorsoftherainbow(red,orange,
green,blue,etc.).Referencethecolorwheel,tosee
howcolorsshiftfromonehuetothenext.

10. (2)Chroma(saturation):Describesthevividnessor
dullnessofcolor.theorangeontherightisvivid,while
thecarrotontheleftappearstobemoredull.
(3) Brightness : which indicates the intensity of light
emitted or reflected by the surface.

11. Our eyes perceive colourwith wavelength of light
ranging from 400 to 700nm.
Three classes of cones:
1
st
class :SWS receptors.
7% in retina i.eBlue cone.
More sensitive to blue violet wavelength around 453
nm.
2
nd
class :MWS receptor
37% in retina i.eGreen cones
Most sensitive to green wavelength around 530 nm.

12. 3
rd
class : LWS receptors .
56% in retina i.e. Red cones.
More sensitive to Red wavelength about 565 nm.

13. COLOR BLINDNESS
Colourblindness (color vision deficiency) is a condition
in which certain colors or shades of colors cannot be
distinguished to some degree or , commonly due to
inherited condition.
Normal colourvision is known as ‘trichromate’.
Color blindness is called daltonism.
Humans beings are born color blind, Photoreceptors are
not developed till the child is 4 months old
Defective perception is anomalous and absence of
colourperception is anopia.

14. There are two principal types of color defect: inherited
(congenital) and acquired.
Congenital CV defect :
X –linked recessive inherited condition.
Major colourblindness is Hereditary (Congenital)
Affects about 8% of men, and approximately 0.5% of
women.

15. Chances of color blindness showing up in men are
much higher than in Female, Female are often,
Carriers of the color deficient gene.
Males only have one X chromosome and therefore
express the genetic disorder.
Diagnosis is typically with themany color test, a
number of other testing methods, includinggenetic
testing, also exist.

16. Color Defects by the Terms Protan,
Deutan, and Tritan
Protan Deutan Tritan
Anomalous
trichromat
Protanomaly Deuteranomaly Tritanomaly
Dichroma Protanopia Deuteranopia Tritanopia

17. Trichromats Dichromats Monochromats
Classification of colourblindness
All 3 types of
cones are
present
2 types of cones are present
Only one type of cone is
present
& only shades of
gray are present
Protanomaly: red weakness
Deuteranomaly: green blindness
Tritanomaly:blue blindness
Protanopia: red blindness
Deuteranopia:Green blindness
Tritanopia:blue blindness

18. Congenital colourblindness:
1.Red-green colourblind (most commonly)
2.affecting males more (5-8%) than females (0.5%)
3.Yellow-blue colourblind are much rare deficiencies
Types:
-Dyschromatopsia
-Achromatopsia

19. Dyschromatopsia
colourconfusion due to
deficiency of mechanism to
perceive coloursand it can be –
•Anomalous trichromatism
•Dichromatism

20. Anomalous trichromaticcolor vision:
appreciate all three primary colourbut have
difficulty distinguishing colors of low saturation.
(partial deficiencies)
-Protanomalous: abnormal level of red pigment.
-Deuteranomalous: abnormal level of green pigment.
-Tritanomalous: abnormal level of blue pigment.

21. Dichromatic colourvision:
faculty to perceive one of three primary coloursis
completely absent-called dichromates.
Types:
-Protanopia: only blue and green cones are functional
(complete red colourdefect).
-Deuteranopia: only blue and red cones are
functional(complete green colourdefect)
-Tritenopia: blue and some green cones are functional
(absence of blue colourappreciation)

22. Red-green deficiency ( prt0nomalous ,protanopia,
deuteranomalous, and deuteranopia) is more common.
Blue deficiency (tritanomalousand tritanopia) is rare.

23. Achromatoiaps:
Itisaveryrareconditionpresentingasconemonochromatismor
rodmonochromatism.
Conemonochromatism–
Itischaracterizedbypresenceofonlyoneprimarycolorandthus
apersonistrulycolourblindbutsuchpatienthavegoodvisual
acuity.
Rodmonochromatism–
itmaybecompleteorincompleteandinheritedasanautosomal
recessivetraitandischaracterizedby:
-Totalcolourblindness
-Poorvisualacuity
-Seeeverythingaswhite,black,orsomeshadeofgray
-Nystagmus
-Normalfundus

24. Prevalence and Inheritance of Color Vision
Defects

25. These color charts show how different colorblind
people see compared to a person with normal
color vision.

26. S.NCongenital color vision defectAcquired color vision defect
1.The defect is the same in each eye
with regard to both type and
severity.
defect may be greater in one eye than in
the
other
2.defect is constant throughout life.defect changes with the progression or
regression of the primary cause.
3.Test results are stable Test results are influenced with changes
in test conditions, such as viewing time
and light level.
4.defect is almost always a red-green defect is frequently a blue-yellow defect
5.Colors of familiar objects are
correctly named.
Changes occur in the color appearance of
familiar objects.
6.No other signs and symptoms defect is always associated with disease
(systemic or ocular),toxicity, or trauma.
7.Inherited defects are more
prevalent in males than females.
Acquired defects are equally prevalent in
males and females
8.Results of color tests are reliable,
and it is easy to
categorize the type of defect
differences in test results from one test to
another,

27. Acquired Color Deficiencies
Acquired color defects are frequently classified as red
green and blue-yellow.
Because of the rarity of inherited tritandefects, a
tritancolor defect is usually acquired.
Achromatopsiamay also be acquired; often the
macula is involved resulting in a reduction in visual
acuity.

28. Summary of the Ocular Diseases and Commonly Used Drugs
Associated with Acquired Color Defects
Diseases:
Red-Green Defects
Optic neuritis
Papillitis
optic atrophy
Toxic amblyopia
Lesions of the optic nerve and pathway
Dominant cystoidmacular dystrophy
Hereditary juvenile macular degeneration
ref.borisclinical refraction

29. Blue-Yellow Defects
Glaucoma*
Diabetes
Retinal detachment
Age-related maculopathy
Chorioretinitis
Central serous retinopathy
Papilledema
Hereditary autosomaldominant optic atrophy

30. Drugs induced cvD
Red-Green Defects
Antidiabetics(oral)
Tuberculostatics
Blue-Yellow Defects
Erythromycin : antibiotic used to treat bacterial infections.
Indomethacin: to treat osteoarthritis,rheumatoid
arthritis,gouty arthritis, orankylosingspondylitis.
Trimethadione: anti-epileptic medication.
Chloroquinederivatives :Antimalarialmedications.
Phenothiazinederivatives : antipsychoticsmedication.

31. Red-Green and/or Blue-Yellow Defects
Ethanol : in management oftoxicity due to ingestion of
methanol, or ethylene glycol.
Cardiac glycosides : for improving the cardiac function.
Oral contraceptives.

32. Thediagnosisofthespecifictypeofacquired
colordefectcanleadtocluesaboutthesiteinthe
visualsystematwhichtheanomalylies,andthismay
facilitatethedifferentialdiagnosisoftheunderlying
diseaseorcause.
Diagnosismayallowaperson'stochangetheirmethod
ofteachingtoaccommodatethedecreasedabilityto
recognizecolors.

33. Reference.
BORISH'S CLINICAL Refraction, SECOND EDITION
CLINICAL PROCEDURES IN OPTOMETRY.
Diagnostic Procedures in OPHTHALMOLOGY ,SECOND EDITION
Journals.

34. Thank
you..
..for your valuable time..