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Color blindness
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====Red–green color blindness==== Red–green color blindness includes '''protan''' and '''deutan''' CVD. Protan CVD is related to the L-cone and includes protanomaly (anomalous trichromacy) and protanopia (dichromacy). Deutan CVD is related to the M-cone and includes deuteranomaly (anomalous trichromacy) and deuteranopia (dichromacy).<ref name=pmid21774112> {{cite journal | last = Wong |first = B. | date = June 2011 | title = Color blindness | journal = Nature Methods | volume = 8 | issue = 6 | pages = 441 | s2cid = 36690778 | pmid = 21774112 | doi = 10.1038/nmeth.1618 }} </ref><ref>{{cite journal | vauthors = Neitz J, Neitz M | title = The genetics of normal and defective color vision | journal = Vision Research | volume = 51 | issue = 7 | pages = 633–51 | date = April 2011 | pmid = 21167193 | pmc = 3075382 | doi = 10.1016/j.visres.2010.12.002 }}</ref> The phenotype (visual experience) of deutans and protans is quite similar. Common colors of confusion include red/brown/green/yellow as well as blue/purple. Both forms are almost always symptomatic of [[congenital red–green color blindness]], so affects males disproportionately more than females.<ref name=harrison>{{cite book|last1=Harrison|first1=G.A.|last2=Tanner|first2=J.M.|last3=Pilbeam|first3=D.R.|last4=Baker|first4=P.T.|title=Human Biology|pages=[https://archive.org/details/humanbiologyintr00gaha/page/183 183–187, 287–290]|location=Oxford|publisher=Oxford University Press|date=1988|isbn=978-0-19-854144-8|url=https://archive.org/details/humanbiologyintr00gaha/page/183}}</ref> This form of color blindness is sometimes referred to as ''daltonism'' after [[John Dalton (scientist)|John Dalton]], who had red–green dichromacy. In some languages, ''daltonism'' is still used to describe red–green color blindness. [[File:ConeMosaics.jpg|thumb|upright=1.4|Illustration of the distribution of cone cells in the [[Fovea centralis|fovea]] of an individual with normal color vision (left), and a color blind (protanopic) retina. The center of the fovea holds very few blue-sensitive cones.]] {{anchor|Protanopia}} {{anchor|Protanomaly}} {{anchor|Protan}} * '''Protan''' (2% of males): Lacking, or possessing anomalous [[OPN1LW|L-opsins]] for long-wavelength sensitive cone cells. Protans have a neutral point at a [[cyan]]-like wavelength around 492 nm (see [[spectral color]] for comparison)—that is, they cannot discriminate light of this wavelength from [[white]]. For a protanope, the brightness of red is much reduced compared to normal.<ref name="Genetics">{{cite journal|last1=Neitz|first1=Jay|first2=Maureen|last2=Neitz|title=The genetics of normal and defective color vision|journal=Vision Research|volume=51|issue=7|date=2011|pages=633–651| doi=10.1016/j.visres.2010.12.002|pmid=21167193|pmc=3075382}}</ref> This dimming can be so pronounced that reds may be confused with black or dark gray, and red traffic lights may appear to be extinguished. They may learn to distinguish reds from yellows primarily on the basis of their apparent brightness or lightness, not on any perceptible hue difference. [[shades of violet|Violet]], [[shades of purple|lavender, and purple]] are indistinguishable from various [[shades of blue]]. A very few people have been found who have one normal eye and one protanopic eye. These ''unilateral dichromats'' report that with only their protanopic eye open, they see wavelengths shorter than neutral point as blue and those longer than it as yellow. {{anchor|Deuteranopia}} {{anchor|Deuteranomaly}} {{anchor|Deutan}} * '''Deutan''' (6% of males): Lacking, or possessing anomalous [[OPN1MW|M-opsin]]s for medium-wavelength sensitive cone cells. Their neutral point is at a slightly longer wavelength, 498 nm, a more greenish hue of cyan. Deutans have the same hue discrimination problems as protans, but without the dimming of long wavelengths. Deuteranopic unilateral dichromats report that with only their deuteranopic eye open, they see wavelengths shorter than neutral point as blue and longer than it as yellow.<ref>{{cite book |title= Contributions to color science |editor1-last= MacAdam |editor1-first=David L. |editor2-last=Judd |editor2-first=Deane B. |publisher=NBS |year=1979 |page=584 |url=https://books.google.com/books?id=jgz_iI8NAzYC&pg=PA584}}</ref>
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