Color Blindness

Inherited color vision deficiency, red green most common

Overview

Color blindness, or color vision deficiency, is a reduced ability to distinguish certain colors. The most common forms are red green deficiencies, the protan and deutan types, caused by variants in the genes for the long and medium wavelength cone opsins on the X chromosome. Because of this X linked inheritance, red green deficiency is far more common in males, affecting about 8 percent of men and 0.5 percent of women of Northern European ancestry. Blue yellow, or tritan, deficiency is rarer and not X linked, and complete absence of color vision, achromatopsia, is rarer still. The English chemist John Dalton described his own color deficiency in 1798, and the condition is still sometimes called daltonism. Diagnosis commonly uses pseudoisochromatic plates such as the Ishihara test, with arrangement tests and anomaloscopes used for classification. Color vision deficiency can affect everyday tasks, and color vision standards apply in some occupations such as aviation. Tinted lenses can alter color contrast but do not restore normal color vision.