Editing Color blindness (section)

==Classification==
[[File:Color blindness.svg|thumb|upright=1.5|These color charts show how different color blind people see compared to a person with normal color vision.{{Dubious|date=March 2023}}]]
Much terminology has existed and does exist for the classification of color blindness, but the typical classification for color blindness follows the [[Von Kries transform|von Kries]] classifications,<ref>{{cite journal |last1=von Kries |first1=J. |date=1897 |title=Ueber Farbensysteme |journal=Zeitschrift für Psychologie Physiologie Sinnesorg |volume=13 |pages=241–324}}</ref> which uses severity and affected cone for naming.

===Based on severity===
Based on clinical appearance, color blindness may be described as total or partial. Total color blindness (monochromacy) is much less common than partial color blindness.<ref>{{cite web |url=http://micro.magnet.fsu.edu/primer/lightandcolor/humanvisionhome.html |title=Human Vision and Color Perception |publisher=[[Florida State University]] |last1=Spring |first1=Kenneth R. |first2=Matthew J. |last2=Parry-Hill |first3=Thomas J. |last3=Fellers |first4=Michael W. |last4=Davidson |access-date=2007-04-05 |url-status=live |archive-url=https://web.archive.org/web/20070827191749/http://micro.magnet.fsu.edu/primer/lightandcolor/humanvisionhome.html |archive-date=2007-08-27 }}</ref>  Partial color blindness includes dichromacy and anomalous trichromacy, but is often clinically defined as mild, moderate or strong.

====Monochromacy====
{{Main|Monochromacy}}
Monochromacy is often called ''total color blindness'' since there is no ability to see color. Although the term may refer to acquired disorders such as [[cerebral achromatopsia]], it typically refers to congenital color vision disorders, namely [[Achromatopsia|rod monochromacy]] and [[blue cone monochromacy]]).<ref name=":0">{{cite web|url=http://www.colourblindawareness.org/colour-blindness/types-of-colour-blindness/|title=Types of Colour Blindness|work=Colour Blind Awareness|url-status=live|archive-url=https://web.archive.org/web/20140529052207/http://www.colourblindawareness.org/colour-blindness/types-of-colour-blindness/|archive-date=2014-05-29}}</ref><ref name=blom>
{{cite book |title       = A Dictionary of Hallucinations |first       = Jan Dirk |last        = Blom |publisher   = Springer |year        = 2009 |isbn        = 978-1-4419-1222-0 |page        = 4 |url=https://books.google.com/books?id=KJtQptBcZloC&pg=PA4 |url-status     = live |archive-url  = https://web.archive.org/web/20161227164302/https://books.google.com/books?id=KJtQptBcZloC&pg=PA4 |archive-date = 2016-12-27 }}</ref>

In cerebral achromatopsia, a person cannot perceive colors even though the eyes are capable of distinguishing them. Some sources do not consider these to be true color blindness, because the failure is of perception, not of vision. They are forms of [[visual agnosia]].<ref name=blom/>

[[Monochromacy]] is the condition of possessing only a single channel for conveying information about color. Monochromats are unable to distinguish any colors and perceive only variations in brightness. Congenital monochromacy occurs in two primary forms:
# Rod monochromacy, frequently called complete [[achromatopsia]], where the retina contains no cone cells, so that in addition to the absence of color discrimination, vision in lights of normal intensity is difficult.
# Cone monochromacy is the condition of having only a single class of cone. A cone monochromat can have good pattern vision at normal daylight levels, but will not be able to distinguish hues. Cone monochromacy is divided into classes defined by the single remaining cone class. However, red and green cone monochromats have not been definitively described in the literature. [[Blue cone monochromacy]] is caused by lack of functionality of L (red) and M (green) cones, and is therefore mediated by the same genes as red–green color blindness (on the X chromosome). Peak spectral sensitivities are in the blue region of the visible spectrum (near 440&nbsp;nm). People with this condition generally show [[nystagmus]] ("jiggling eyes"), [[photophobia]] (light sensitivity), reduced [[visual acuity]], and [[myopia]] (nearsightedness).<ref>{{cite journal | vauthors = Weiss AH, Biersdorf WR | title = Blue cone monochromatism | journal = Journal of Pediatric Ophthalmology and Strabismus | volume = 26 | issue = 5 | pages = 218–23 | year = 1989 | doi = 10.3928/0191-3913-19890901-04 | pmid = 2795409 | s2cid = 23037026 }}</ref> Visual acuity usually falls to the 20/50 to 20/400 range.

====Dichromacy====
{{main|Dichromacy}}
Dichromats can match any color they see with some mixture of just two [[primary color]]s (in contrast to those with normal sight ([[Trichromacy|trichromats]]) who can distinguish three primary colors).<ref name=":0" /> Dichromats usually know they have a color vision problem, and it can affect their daily lives. Dichromacy in humans includes protanopia, deuteranopia, and tritanopia. Out of the male population, 2% have severe difficulties distinguishing between red, orange, yellow, and green (orange and yellow are different combinations of red and green light). Colors in this range, which appear very different to a normal viewer, appear to a dichromat to be the same or a similar color. The terms protanopia, deuteranopia, and tritanopia come from Greek, and respectively mean "inability to see (''anopia'') with the first (''prot-''), second (''deuter-''), or third (''trit-'') [cone]".

====Anomalous trichromacy====
Anomalous trichromacy is the mildest type of color deficiency{{Citation needed|date=February 2025}}, but the severity ranges from almost dichromacy (strong) to almost normal trichromacy (mild).<ref>{{cite journal | vauthors = Simunovic MP | title = Colour vision deficiency | journal = Eye | volume = 24 | issue = 5 | pages = 747–55 | date = May 2010 | pmid = 19927164 | doi = 10.1038/eye.2009.251 | doi-access = free }}</ref> In fact, many mild anomalous trichromats have very little difficulty carrying out tasks that require normal color vision and some may not even be aware that they have a color vision deficiency. The types of anomalous trichromacy include protanomaly, deuteranomaly and tritanomaly.  It is approximately three times more common than [[dichromacy]].<ref>{{Cite journal |doi=10.1016/j.gde.2006.04.002|title=Genetics of variation in human color vision and the retinal cone mosaic|year=2006|last1=Deeb|first1=Samir S.|journal=Current Opinion in Genetics & Development|volume=16|issue=3|pages=301–307|pmid=16647849}}</ref> Anomalous trichromats exhibit [[trichromacy]], but the color matches they make differ from normal trichromats. In order to match a given spectral yellow light, protanomalous observers need more red light in a red/green mixture than a normal observer, and deuteranomalous observers need more green. This difference can be measured by an instrument called an [[Anomaloscope]], where red and green lights are mixed by a subject to match a yellow light.<ref>{{cite journal|doi=10.1016/0042-6989(79)90209-8|title=Optimization of a Rayleigh-type equation for the detection of tritanomaly|year=1979|last1=Moreland|first1=J.D.|last2=Kerr|first2=J.|journal=Vision Research|volume=19|issue=12|pages=1369–1375|pmid=316945|s2cid=29379397 }}</ref>

===Based on affected cone===
There are two major types of color blindness: difficulty distinguishing between red and green, and difficulty distinguishing between blue and yellow.<ref>{{cite web|url=http://www.digitalspaceart.com/articles/ColorBlindness.pdf |title=Accommodating Color Blindness |first=Paul S. |last=Hoffman |access-date=2009-07-01 |url-status=dead |archive-url=https://web.archive.org/web/20080515103432/http://www.digitalspaceart.com/articles/ColorBlindness.pdf |archive-date=15 May 2008 }}</ref><ref>{{cite web|url=http://healthlink.mcw.edu/article/999211295.html |title=Severity of Colorblindness Varies |last=Neitz |first=Maureen E. |author-link= Maureen Neitz |publisher=[[Medical College of Wisconsin]] |access-date=2007-04-05 |url-status=dead |archive-url=https://web.archive.org/web/20070205055320/http://healthlink.mcw.edu/article/999211295.html |archive-date=5 February 2007 }}</ref>{{Dubious |Tritanopia|date=September 2020}} These definitions are based on the [[phenotype]] of the partial color blindness. Clinically, it is more common to use a genotypical definition, which describes which [[cone cell|cone]]/[[opsin]] is affected.

====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&nbsp;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&nbsp;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>

====Blue–yellow color blindness====
Blue–yellow color blindness includes '''tritan''' CVD. Tritan CVD is related to the S-cone and includes tritanomaly (anomalous trichromacy) and tritanopia (dichromacy). Blue–yellow color blindness is much less common than red–green color blindness, and more often has acquired causes than genetic. Tritans have difficulty discerning between bluish and greenish hues.<ref>Steefel, Lorraine T., and Timothy E. Moore, PhD. "Color Blindness." ''The Gale Encyclopedia of Nursing and Allied Health'', edited by Jacqueline L. Longe, 4th ed., vol. 2, Gale, 2018, pp. 890–892. ''Gale eBooks'', Accessed 29 Dec. 2021.</ref> Tritans have a neutral point at 571&nbsp;nm (yellowish).<ref>{{Cite journal |last=Graham |first=C. H. |last2=Hsia |first2=Y. |date=1958-03-28 |title=Color defect and color theory; studies of normal and colorblind persons, including a subject color-blind in one eye but not in the other |url=https://pubmed.ncbi.nlm.nih.gov/13529033/ |journal=Science |volume=127 |issue=3300 |pages=675–682 |doi=10.1126/science.127.3300.675 |issn=0036-8075 |pmid=13529033}}</ref><ref>{{Cite web |title=SBFAQ Part 4: Color Blindness |url=https://visualexpert.com/Resources/cfaqPart4.html |access-date=2025-03-09 |website=visualexpert.com}}</ref>

{{anchor|Tritanopia}}
{{anchor|Tritanomaly}}
{{anchor|Tritan}}
* '''Tritan''' (<&nbsp;0.01% of individuals): Lacking, or possessing anomalous [[OPN1SW|S-opsins]] or short-wavelength sensitive cone cells. Tritans see short-wavelength colors ([[blue]], [[indigo]] and spectral [[Violet (color)|violet]]) as greenish and drastically dimmed, some of these colors even as [[black]]. Yellow and orange are indistinguishable from [[white]] and [[pink]] respectively, and purple colors are perceived as various [[shades of red]]. Unlike protans and deutans, the mutation for this color blindness is carried on chromosome 7. Therefore, it is not sex-linked (equally prevalent in both males and females). The OMIM gene code for this mutation is 304000 "Colorblindness, Partial Tritanomaly".<ref>{{cite web | title = Disease-causing Mutations and protein structure |url=http://www.biochem.ucl.ac.uk/bsm/humgen/chr__034.html#304000 | archive-url=https://web.archive.org/web/20050501081119/http://www.biochem.ucl.ac.uk/bsm/humgen/chr__034.html#304000 | url-status = dead | archive-date = 2005-05-01 | publisher = UCL Biochemistry BSM Group | access-date = 2007-04-02 }}</ref>
{{anchor|Tetartanopia}}
{{anchor|Tetartanomaly}}
{{anchor|Tetartan}}
* '''Tetartan''' is a hypothetical "fourth type" of color blindness, and a type of blue–yellow color blindness. Given the molecular basis of human color vision, it is unlikely this type could exist.<ref>{{Cite journal |last1=V |first1=Ionica |last2=Gastaud |first2=P |title=Test chromatique pour dépistage et étalonnage des dyschromatopsies |trans-title=Color vision test for detection and evaluation of dyschromatopsia |url=https://pubmed.ncbi.nlm.nih.gov/9033889/ |journal=Journal Français d'Ophtalmologie |date=1996 |language=fr |volume=19 |issue=11 |pages=679–688 |pmid=9033889 |access-date=13 June 2024 |archive-date=13 June 2024 |archive-url=https://web.archive.org/web/20240613193630/https://pubmed.ncbi.nlm.nih.gov/9033889/ |url-status=live }}</ref>

===Summary of cone complements===
The below table shows the cone complements for different types of human color vision, including those considered color blindness, normal color vision and 'superior' color vision. The cone complement contains the types of cones (or their opsins) expressed by an individual.
{|class="wikitable"
|- style="background:#eaecf0;color:#000000;"
|colspan="2" rowspan="2" style="text-align:right; vertical-align:top;"|Cone system
|colspan="2"|Red  || rowspan="13" style="font-size:1px;" |
|colspan="2"|Green|| rowspan="13" style="font-size:1px;" |
|colspan="2"|Blue
|colspan="3" rowspan="2" style="vertical-align:bottom;"|'''N'''&nbsp;=&nbsp;normal<br />'''A'''&nbsp;=&nbsp;anomalous
|- style="background:#eaecf0;color:#000000;"
|'''N'''||'''A'''||'''N'''||'''A'''||'''N'''||'''A'''
|-
|style="text-align:right;"|1||Normal vision
|style="background:#FF0000"| ||style="background:#000000"|
|style="background:#00FF00"| ||style="background:#000000"|
|style="background:#0000FF"| ||style="background:#000000"|
|Trichromacy||colspan="2"|Normal
|- style="border-top:double #a2a9b1;"
|style="text-align:right;"|2||Protanomaly
|style="background:#000000"| ||style="background:#FF0000"|
|style="background:#00FF00"| ||style="background:#000000"|
|style="background:#0000FF"| ||style="background:#000000"|
|Anomalous trichromacy
|rowspan="6"|Partial<br />color<br />blindness||rowspan="4"|Red–<br />green
|-
|style="text-align:right;"|3||Protanopia
|style="background:#000000"| ||style="background:#000000"|
|style="background:#00FF00"| ||style="background:#000000"|
|style="background:#0000FF"| ||style="background:#000000"|
|Dichromacy
|- style="border-top:2px solid #a2a9b1;"
|style="text-align:right;"|4||Deuteranomaly
|style="background:#FF0000"| ||style="background:#000000"|
|style="background:#000000"| ||style="background:#00FF00"|
|style="background:#0000FF"| ||style="background:#000000"|
|Anomalous trichromacy
|-
|style="text-align:right;"|5||Deuteranopia
|style="background:#FF0000"| ||style="background:#000000"|
|style="background:#000000"| ||style="background:#000000"|
|style="background:#0000FF"| ||style="background:#000000"|
|Dichromacy
|- style="border-top:2px solid #a2a9b1;"
|style="text-align:right;"|6||Tritanomaly
|style="background:#FF0000"| ||style="background:#000000"|
|style="background:#00FF00"| ||style="background:#000000"|
|style="background:#000000"| ||style="background:#0000FF"|
|Anomalous trichromacy||rowspan="2"|Blue–<br />yellow
|-
|style="text-align:right;"|7||Tritanopia
|style="background:#FF0000"| ||style="background:#000000"|
|style="background:#00FF00"| ||style="background:#000000"|
|style="background:#000000"| ||style="background:#000000"|
|Dichromacy
|- style="border-top:double #a2a9b1;"
|style="text-align:right;"|8||Blue cone monochromacy
|style="background:#000000"| ||style="background:#000000"|
|style="background:#000000"| ||style="background:#000000"|
|style="background:#0000FF"| ||style="background:#000000"|
|rowspan="2"|Monochromacy
|colspan="2" rowspan="2"|Total color blindness
|-
|style="text-align:right;"|9||Achromatopsia
|style="background:#000000"| ||style="background:#000000"|
|style="background:#000000"| ||style="background:#000000"|
|style="background:#000000"| ||style="background:#000000"|
|- style="border-top:double #a2a9b1;"
| style="text-align:right;" |10|| rowspan="2" |Tetrachromacy<br />(carrier theory)
| style="background:#FF0000" | || style="background:#FF0000" |
| style="background:#00FF00" | || style="background:#000000" |
| style="background:#0000FF" | || style="background:#000000" |
| rowspan="2" |Tetrachromacy
| colspan="2" rowspan="2" |'Superior'
|-
| style="text-align:right;" | 11
| style="background:#FF0000" | || style="background:#000000" |
| style="background:#00FF00" | || style="background:#00FF00" |
| style="background:#0000FF" | || style="background:#000000" |
|}