Color blindness or color vision deficiency is the inability or decreased ability to see color, or distinguish color differences, under normal lighting conditions. Color blindness affects many people in a population. "Color blind" is a term of art; there is no actual blindness but there is a fault in the development of one or more sets of retinal cones that perceive color in light and transmit that inform ation to the optic nerve. Symptoms like those of color blindness can also be produced by physical or chemical damage to the eye, the optic nerve, or parts of the brain. These damages are not true color blindness, as defined. The English chemist John Dalton published the first scientific paper on this subject in 1798, "Extraordinary facts relating to the vision of colours", after the realization of his own color blindness. Because of Dalton's work, the general condition has been called daltonism. Color blindness is usually classed as a slight disability; but there are situations where it can give an advantage. Some studies conclude that color blind people are better at penetrating certain color camouflages. Such findings may give an evolutionary reason for the high prevalence of red–green color blindness.
Types of color vision deficiency
* Monochromatism: Either no cones are available or just one type of them is. * Dichromatism: Only two different cone types are found, the third one is missing completely. * Anomalous trichromatism: All three types are present but with shifted peaks of sensitivity for one of them. This results in a smaller color spectrum. Dichromats and anomalous trichromats exist again in three different types according to the missing cone or in the latter case of its malfunctioning. * Tritanopia: Missing/failure of the S -cone (blue).
* Deuteranopia: Missing/failure of the M-cone (green).
* Protanopia: Missing/failure of the L-cone (red).
Here are some illustrations of the most common forms of color-blindness:
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