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Color blindness or color vision deficiency (CVD) is the decreased ability to see color or differences in color. The severity of color blindness ranges from mostly unnoticeable to full absence of color perception. Color blindness is usually an inherited problem or variation in the functionality of one or more of the three classes of cone cells in the retina, which mediate color vision. The most common form is caused by a genetic condition called congenital red–green color blindness (including protan and deutan types), which affects up to 1 in 12 males (8%) and 1 in 200 females (0.5%). The condition is more prevalent in males, because the opsin genes responsible are located on the X chromosome. Rarer genetic conditions causing color blindness include congenital blue–yellow color blindness (tritan type), blue cone monochromacy, and achromatopsia. Color blindness can also result from physical or chemical damage to the eye, the optic nerve, parts of the brain, or from medication toxicity. Color vision also naturally degrades in old age. Diagnosis of color blindness is usually done with a color vision test, such as the Ishihara test. There is no cure for most causes of color blindness, however there is ongoing research into gene therapy for some severe conditions causing color blindness. Minor forms of color blindness do not significantly affect daily life and the color blind automatically develop adaptations and coping mechanisms to compensate for the deficiency. However, diagnosis may allow an individual, or their parents/teachers to actively accommodate the condition. Color blind glasses (e.g. EnChroma) may help the red–green color blind at some color tasks, but they do not grant the wearer "normal color vision" or the ability to see "new" colors. Some mobile apps can use a device's camera to identify colors. Depending on the jurisdiction, the color blind are ineligible for certain careers, such as aircraft pilots, train drivers, police officers, firefighters, and members of the armed forces. The effect of color blindness on artistic ability is controversial, but a number of famous artists are believed to have been color blind. Effects A color blind person will have decreased (or no) color discrimination along the red–green axis, blue–yellow axis, or both. However, the vast majority of the color blind are only affected on their red–green axis. The first indication of color blindness generally consists of a person using the wrong color for an object, such as when painting, or calling a color by the wrong name. The colors that are confused are very consistent among people with the same type of color blindness. Confusion colors Confusion colors are pairs or groups of colors that will often be mistaken by the color blind. Confusion colors for red–green color blindness include: cyan and grey rose-pink and grey blue and purple yellow and neon green red, green, orange, brown Confusion colors for tritan include: yellow and grey blue and green dark blue/violet and black violet and yellow-green red and rose-pink These colors of confusion are defined quantitatively by straight confusion lines plotted in CIEXYZ, usually plotted on the corresponding chromaticity diagram. The lines all intersect at a copunctal point, which varies with the type of color blindness. Chromaticities along a confusion line will appear metameric to dichromats of that type. Anomalous trichromats of that type will see the chromaticities as metameric if they are close enough, depending on the strength of their CVD. For two colors on a confusion line to be metameric, the chromaticities first have to be made isoluminant, meaning equal in lightness. Also, colors that may be isoluminant to the standard observer may not be isoluminant to a person with dichromacy. Color tasks Cole describes four color tasks, all of which are impeded to some degree by color blindness: Comparative – When multiple colors must be compared, such as with mixing paint Connotative – When colors are given an implicit meaning, such as red = stop Denotative – When identifying colors, for example by name, such as "where is the yellow ball?" Aesthetic – When colors look nice – or convey an emotional response – but do not carry explicit meaning The following sections describe specific color tasks with which the color blind typically have difficulty. Food Color blindness causes difficulty with the connotative color tasks associated with selecting or preparing food. Selecting food for ripeness can be difficult; the green–yellow transition of bananas is particularly hard to identify. It can also be difficult to detect bruises, mold, or rot on some foods, to determine when meat is done by color, to distinguish some varietals, such as a Braeburn vs. a Granny Smith apple, or to distinguish colors associated with artificial flavors (e.g. jelly beans, sports drinks). Skin color Changes in skin color due to bruising, sunburn, rashes or even blushing are easily missed by the red–green color blind. Traffic lights The colors of traffic lights can be difficult for the red–green color blindness. This difficulty includes distinguishing red/amber lights from sodium street lamps, distinguishing green lights (closer to cyan) from normal white lights, and distinguishing red from amber lights, especially when there are no positional clues available (see image). The main coping mechanism to overcome these challenges is to memorize the position of lights. The order of the common triplet traffic light is standardized as red–amber–green from top to bottom or left to right. Cases that deviate from this standard are rare. One such case is a traffic light in Tipperary Hill in Syracuse, New York, which is upside-down (green–amber–red top to bottom) due to the sentiments of its Irish American community. However, the light has been criticized due to the potential hazard it poses for color blind drivers. There are other several features of traffic lights available that help accommodate the color blind. British Rail signals use more easily identifiable colors: The red is blood red, the amber is yellow and the green is a bluish color. Most British road traffic lights are mounted vertically on a black rectangle with a white border (forming a "sighting board"), so that drivers can more easily look for the position of the light. In the eastern provinces of Canada, traffic lights are sometimes differentiated by shape in addition to color: square for red, diamond for yellow, and circle for green (see image). Signal lights Navigation lights in marine and aviation settings employ red and green lights to signal the relative position of other ships or aircraft. Railway signal lights also rely heavily on red–green–yellow colors. In both cases, these color combinations can be difficult for the red–green color blind. Lantern Tests are a common means of simulating these light sources to determine.... Discover the I D Blind popular books. Find the top 100 most popular I D Blind books.