7.2 Classification of Congenital Colour Vision Defects
Description
This article is from the Vision and Eye Care FAQ, by grants@research.canon.com.au (Grant Sayer) with numerous contributions by others.
7.2 Classification of Congenital Colour Vision Defects
Colour vision defects are classified via the number of primary spectral
colours which an individual requires to match any other spectral colour.
The normal individual usually requires 3 primaries and is classified as
a trichromat.
(a) Achromatic (Monochromatic) Colour Vision
+ no colour vision
+ only light - dark discrimination
+ lack of retinal function (typical case)
+ higher centre defects (generally atypical)
(b) Dichromatic Colour Vision
+ colour distinctions of 2 kinds (achromatic or R-G/Y-B)
+ 4 types
- protanopia and deutranopia (confusion of colours from green
through yellow to red)
- tritanopia and tetartanopia (confusion of colours from blue
through green to yellow.
(c) Trichromatic Colour Vision
+ anomalous type requires 3 stimulus primaries to match stimuli
but matches are outside the normal range
+ 3 types - protan, deutran, tritan
The colour defective person has difficult in distinguising colours that
are on "confusion lines". For example, protanopes confuse blue-greens
(and greys) with red (and browns). The deutranopes make mistakes with
blue-greens and purple. While tritanopes confuse yellow with violet.
The last dichromat group; tetartanopes, confuse yellow with blue. The
anomalous types have difficulty with light tints and dark shades.
Colour defective vision is inherited as a sex-linked recessive characteristic.
It is more common in men than women. The most common defect is
deutranomoly with an incidence of 5% or males, protanomaly affects 1.5% and
protanopia and deutranopia about 1% each.
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