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Untitled Document
Color blindness, in the formal medical term, color vision deficiency is any abnormality of the color vision system that causes a person to see colors differently than most people or to have difficulty distinguishing among certain colors.
Color vision deficiency is detected by tests that use special color plates under daylight conditions. The test usually is conducted during the childhood years. It is also performed when an adult applies for a job in which color vision is essential, such as airline pilot. The exact degree of color vision deficiency can be determined by a test that requires the arrangement of sequences of colored chips or by an instrument called an anomaloscope, which shines a mixture of red and green lights. The person being tested adjusts the mixture until it appears the same as a fixed spot of yellow light. An adjustment that yields a mixture that is too red or too green indicates the presence and severity of color vision deficiency.
Many people with color vision deficiency are not aware of the problem because it does not interfere with everyday living. It can be detected during employment tests for an occupation requiring normal color vision. Such positions include airline pilot, commercial artist, marine pilot, color photographer, or electrician, where the ability to distinguish color-coded wires is important. There is no treatment for the condition.
A person with color blindness is unable to distinguish some or all of the colors visible to a person with normal color vision.
Color blindness falls into three sub-categories:
- Monochromacy
Monochromacy, also known as “total color blindness”, is the lack of ability to distinguish colors; caused by cone defect or absence. Monochromacy occurs when two or all three of the cone pigments are missing and color and lightness vision is reduced to one dimension.
- Dichromacy
Dichromacy is a moderately severe color vision defect in which one of the three basic color mechanisms is absent or not functioning. It is hereditary and sex-linked, affecting predominantly males. Dichromacy occurs when one of the cone pigments is missing and color is reduced to two dimensions.
- Trichromacy
Anomalous trichromacy is a common type of inherited color vision deficiency, occurring when one of the three cone pigments is altered in its spectral sensitivity. This results in an impairment, rather than loss, of trichromacy (normal three-dimensional color vision)
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