Color Vision Deficiency

Topics: Color blindness, Color, Color vision Pages: 5 (1613 words) Published: June 4, 2012
Color Vision Deficiency
Eight out of every one hundred men and one out of every two hundred women, or 8% of men and .5% of women, has a color vision deficiency, commonly known as color blindness (Color Vision). The first documented case was in1792 by John Dalton, better known for his atomic theory, who discovered he was color blind himself when viewing a pink flower that appeared to be blue to him. "I accidently observed the colour of the flower geranium zonale by candlelight. The flower was pink, but it appeared to me almost an exact sky-blue by day; in candlelight it was astonishingly changed; not having then any blue in it but being what I call red, a colour which forms a striking contrast to blue,"(sic)(Snyder). Color vision deficiency is the inability to distinguish certain shades of color, or in more severe cases, see only black and white. The severity of color vision deficiency can range from a minor disability to a severe disability depending on the cause. Color blindness will affect both eyes if it is inherited and most likely just one if the cause for the deficiency is aging, medication, or illness. Color sight is important in many everyday tasks, such a driving a car, or transcribing notes at school written on a whiteboard in red or green. It can be extremely difficult to decipher graphs and charts because the colors in use cannot be distinguished between by a person with color vision defects. Individuals with color vision defects are excluded by law from certain occupations such as a police officer, firefighter, pilot, or public transportation driver (Color Vision Defects) Although in some rare instances, color blindness has its’ advantages, in “World War II, colorblind men were sent on special missions because their decreased ability to see green led to an increased ability to see through camouflage” (Turner). Color vision deficiency has no known cure, is a vision defect that is difficult to understand, affects primarily men in varying degrees, and creates a multitude of issues in daily lives. Deuteranomaly, deuteranopia, protanomaly, protanopia, tritanomaly, tritanopia, and monochromacy are the technical terms of color vision deficiencies that involve the retina, cones, and rods that can be found in healthy eyes (What). The retina, a light-sensitive tissue at the back of the eye, contains two types of light receptor cells called rods and cones. These cells transmit visual signals from the eye to the brain. Rods are responsible for vision in low light. Cones provide vision in bright light, including colour vision. Three types of cones each contain a special pigment (a photopigment) that is most sensitive to a particular wavelength of light. The brain combines input from all three types of cones to produce normal colour vision (sic) (Colour). The three types of cones found in an individual with trichromatic vision (normal vision) are blue, green and red or S, M, and L respectively, and each has a different sensitivity light of different lengths. S-cones, are sensitive to short wavelength light (blue), M-cone are sensitive to medium wavelength light (green), and L-cones are sensitive to long wavelength light (red) (Rods). An individual, whose cones do not function properly or has missing cones, sends the wrong message through the optic nerve to the brain enabling the incorrect distinguishing of color or color vision deficiency. In monochromic vision, the worst of the defects, cones do not exist or just one type can be found and individuals see in black, white, and grays only. The most common type is red-green color blindness or deuteranomaly/deuteranopia and protanomaly/protanopia; it accounts for 99% of all color vision defects. Tritanomaly/tritanopia the S-cone is missing or malfunctioning that allows blue hues to be distinguishable. Several causes for color vision deficiency exist but heredity accounts for the largest percentage of defects. In the majority of...
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