Color Blindness Color blindness is a misleading term that is used to describe a wide range of color deficiencies. Complete color blindness is extremely rare. Color deficiencies can usually be attributed to genetics, but it is also possible to acquire them through eye, nerve, or brain damage. About 10% of American males are "color blind" in varying types and degrees, and I am one of them! Some individuals can go their whole lives without realizing they are color blind, depending on the type and severity of their condition. The different types of color blindness can first be divided into the following categories: red-green color blindness, blue-yellow color blindness, and monochromacy (complete color blindness). Red-green is the most common form of color blindness. Blue-yellow color blindness is rare and distributed equally among males and females. Monochromacy is extremely rare except in certain isolated societies (such as the island of Pohnpei). But these are all biological issues that you will have to look into on your own time! Blue-yellow color blindness is caused by inactivation of the short-wavelength cone cells. Monochromacy has two causes. If a person only has one functioning set of cone cells, they will be completely color blind. If a person has no functioning sets of cone cells, their vision relies entirely upon their rod cells, which also makes them completely color blind. Red-green color blindness can be divided into the following categories: Protanopia Individuals with this type of color deficiency lack the cone cells that respond to long-wavelength light. Therefore, since they only have two types of cone cells, their human color space can be reduced to two dimensions. This means that any color they perceive can be created with a mixture of only two primary colors. This is a rare form of color blindness. Deuteranopia This is similar to protanopia except that individuals afflicted with this condition lack the cone cells that respond to medium-wavelength light. Just as with protanopia, the human color space of individuals with deuteranopia can be reduced to two dimensions. This is another rare form of color blindness, making up about 1% of the American male population. Protanomaly The long-wavelength cones of people with this type of color deficiency have a mutated sensitivity to light. The sensitivity distribution for the long-wavelength cones is shifted towards the short-wavelength side of the color spectrum. Subsequently, mixed colors do not appear the same to these individuals as they would with normal color vision. Also, "this causes reds to reduce in intensity to the point where they can be mistaken for black" (Wikipedia). About 1% of American males have this type of color deficiency, including me! Original picture from: http://en.wikipedia.org/wiki/Color Deuteranomaly This is similar to protanomaly except that it refers to a mutated sensitivity of the medium-wavelength cones where the distribution is shifted toward the long-wavelength side of the color spectrum. However, "unlike protanomaly the intensity of colors is unchanged" (Wikipedia). Deuteranomaly is the most common form of color blindness, occurring in about 8% of American males. Original picture from: http://en.wikipedia.org/wiki/Color The Ishihara Test for Color Blindness Below are two examples of the Ishihara test for color blindness. Individuals with normal color vision should see a number formed out of the dots. Individuals who are red-green color blind will only see a circle of dots with nothing inside. These tests are not foolproof, however, because even the different types of color blindness can afflict people in varying degrees (corresponding to the number of cone cells missing in the cases of protanopia or deuteranopia, or the degree to which a sensitivity distribution is shifted in the cases of protanomaly and deuteranomaly). I chose these two Ishihara test examples specifically because I don't see anything inside of them. Both pictures from: http://www.toledo-bend.com/colorblind/Ishihara.html

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