Color blindness or color vision deficiency is the inability or decreased ability to see color, or perceive color differences, under lighting conditions when color vision is not normally impaired. "Color blind" is a term of art; there is no actual blindness but there is a fault in the development of either or both sets of retinal cones that perceive color in light and transmit that information to the optic nerve. The gene that causes color blindness is carried on the X chromosome, making the handicap far more common among men (who have just one X chromosome) than among women (who have two, so must inherit the gene from both parents).
The symptoms of color blindness also can be produced by physical or chemical damage to the eye, optic nerve, or the brain generally. These are not true color blindness, however, but they represent conditions of limited actual blindness. Similarly, a person with achromatopsia, although unable to see colors, is not "color blind" per se but they suffer from a completely different disorder, of which atypical color deficiency is only one manifestation.
Click HERE to take the Test
