Color Blindness

From Citizendium, the Citizens' Compendium

Color blindness is a defect of vision affecting the ability to distinguish colors. This condition is caused by a defect in the retina or in other nerve portions of the eye. It occurs most often in males.

The first detailed report on color blindness was written by the British chemist John Dalton, who was himself afflicted with it.

Total color blindness, in which all hues are perceived as variations of gray, is known as achromatopsia or monochromatism. This condition is congenital, extremely rare, and affects men and women almost equally. Color blindness also may occur as a temporary condition following a serious illness.

Partial color blindness, called dichromatism, consists generally of the inability to differentiate between reds and greens or to perceive either reds or greens; infrequently, the confusion may involve blues and yellows. Dichromatism is the most common form of color blindness, affecting about seven percent of men and less than one percent of women. Dichromatism is identified as a sex-linked hereditary characteristic.

The vision of most color-blind people is normal in all other respects. In addition, color-blind people can generally learn by experience to associate certain colors with varying sensations of brightness. Consequently, many color-blind persons are unaware that they are color-blind.