Color blindness (color vision deficiency) is the decreased ability to see color or differences in color. It can impair tasks such as selecting ripe fruit, choosing clothing, and reading traffic lights. Color blindness may make some educational activities more difficult. However, problems are generally minor, and most color-blind people adapt. People with total color blindness (achromatopsia) may also be uncomfortable in bright environments and have decreased visual acuity.
|Other names||Colour blindness, color deficiency, impaired color vision|
|An Ishihara color test plate. With properly configured computer displays, people with normal vision should see the number "74". Viewers with red-green color blindness will read it as "21", and those with total color blindness may not see any numbers.|
|Symptoms||Decreased ability to see colors|
|Causes||Genetic (inherited usually X-linked)|
|Diagnostic method||Ishihara color test|
|Treatment||Adjustments to teaching methods, mobile apps|
|Frequency||Red–green: 8% males, 0.5% females (Northern European descent)|
The most common cause of color blindness is an inherited problem in the development of one or more of the three sets of the eyes' cone cells, which sense color. Among humans, males are more likely to be color blind than females, because the genes responsible for the most common forms of color blindness are on the X chromosome. Females have two X chromosomes, so a defect in one is typically compensated for by the other. Non-color-blind females can carry genes for color blindness and pass them on to their children. Males only have one X chromosome and therefore always express the genetic disorder if they have the recessive gene. Color blindness can also result from physical or chemical damage to the eye, the optic nerve, or parts of the brain. Diagnosis is typically with the Ishihara color test; other methods include genetic testing.
There is no cure for color blindness. Diagnosis may allow a person's teacher to change the teaching method to accommodate the condition. Special lenses such as X-chrome lenses may help people with red–green color blindness in bright light. Mobile apps can help people identify colors.
Red–green color blindness is the most common form, followed by blue–yellow color blindness and total color blindness. Red–green color blindness affects up to 8% of males and 0.5% of females of Northern European descent. The ability to see color also decreases in old age. In certain countries, color blindness may make people ineligible for certain jobs, such as those of aircraft pilots, train drivers, crane operators, and people in the armed forces. The effect of color blindness on artistic ability is controversial. The ability to draw appears to be unchanged, and a number of famous artists are believed to have been color blind.