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Color blindness

Color blindness or color vision deficiency (CVD) is the decreased ability to see color or differences in color.[2] 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.[2] 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%).[2][3] The condition is more prevalent in males, because the opsin genes responsible are located on the X chromosome.[2] 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.[2] Color vision also naturally degrades in old age.[2]

"Colorblind" redirects here. For the disorder that causes most forms of color blindness, see Congenital red–green color blindness. For other uses, see Color blind (disambiguation).

Color blindness

Color vision deficiency, impaired color vision[1]

Ophthalmology

Decreased ability to see colors[2]

Long term[2]

Genetic (inherited usually X-linked)[2]

Ishihara color test[2]

Adjustments to teaching methods, mobile apps[1][2]

Red–green: 8% males, 0.5% females (Northern European descent)[2]

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.[2] 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.[2] However, diagnosis may allow an individual, or their parents/teachers, to actively accommodate the condition.[1] Color blind glasses (e.g. EnChroma) may help the red–green color blind at some color tasks,[2] but they do not grant the wearer "normal color vision" or the ability to see "new" colors.[4] Some mobile apps can use a device's camera to identify colors.[2]


Depending on the jurisdiction, the color blind are ineligible for certain careers,[1] such as aircraft pilots, train drivers, police officers, firefighters, and members of the armed forces.[1][5] The effect of color blindness on artistic ability is controversial,[1][6] but a number of famous artists are believed to have been color blind.[1][7]

Normal sight

Normal sight

Deuteranopic sight

Deuteranopic sight

Protanopic sight

Protanopic sight

Tritanopic sight

Tritanopic sight

Monochromatic sight

Monochromatic sight

Protan (2% of males): Lacking, or possessing anomalous 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.[39] 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. Violet, 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.

L-opsins

Inherited: inherited or congenital/genetic color vision deficiencies are most commonly caused by mutations of the genes encoding opsin proteins. However, several other genes can also lead to less common and/or more severe forms of color blindness.

Acquired: color blindness that is not present at birth, may be caused by chronic illness, accidents, medication, chemical exposure or simply normal aging processes.

[44]

Pseudoisochromatic plates, a classification which includes the and HRR test, embed a figure in the plate as a number of spots surrounded by spots of a slightly different color. These colors must appear identical (metameric) to the color blind but distinguishable to color normals. Pseudoisochromatic plates are used as screening tools because they are cheap, fast, and simple, but they do not provide precise diagnosis of CVD.

Ishihara color test

Lanterns, such as the , project small colored lights to a subject, who is required to identify the color of the lights. The colors are those of typical signal lights, i.e. red, green, and yellow, which also happen to be colors of confusion of red–green CVD. Lanterns do not diagnose color blindness, but they are occupational screening tests to ensure an applicant has sufficient color discrimination to be able to perform a job.

Farnsworth Lantern Test

A red-tint contact lens worn over the non-dominant eye will leverage to improve discrimination of some colors. However, it can make other colors more difficult to distinguish. A 1981 review of various studies to evaluate the effect of the X-chrom (one brand) contact lens concluded that, while the lens may allow the wearer to achieve a better score on certain color vision tests, it did not correct color vision in the natural environment.[59] A case history using the X-Chrom lens for a rod monochromat is reported[60] and an X-Chrom manual is online.[61]

binocular disparity

Tinted glasses (e.g. Pilestone/Colorlite glasses) apply a tint (e.g. magenta) to incoming light that can distort colors in a way that makes some color tasks easier to complete. These glasses can circumvent many , though this is typically not allowed.[62]

color vision tests

Glasses with a (e.g. EnChroma glasses) filter a narrow band of light that excites both the L and M cones (yellow–green wavelengths).[63] When combined with an additional stopband in the short wavelength (blue) region, these lenses may constitute a neutral-density filter (have no color tint). They improve on the other lens types by causing less distortion of colors and will essentially increase the saturation of some colors. They will only work on trichromats (anomalous or normal), and unlike the other types, do not have a significant effect on Dichromats. The glasses do not significantly increase one's ability on color blind tests.[64]

notch filter

In April 2003, Romania removed color blindness from its list of disqualifying conditions for learner driver's licenses.[96] It is now qualified as a condition that could potentially compromise driver safety, therefore a driver may have to be evaluated by an authorized ophthalmologist to determine if they can drive safely. As of May 2008, there is an ongoing campaign to remove the legal restrictions that prohibit color blind citizens from getting driver's licenses.[97]

[95]

In June 2020, India relaxed its ban on driver's licenses for the color blind to now only apply to those with strong CVD. While previously restricted, those who test as mild or moderate can now pass the medical requirements.

[98]

Australia instituted a tiered ban on the color blind from obtaining commercial driver's licenses in 1994. This included a ban for all , and a stipulation that deutans must pass the Farnsworth Lantern. The stipulation on deutans was revoked in 1997 citing a lack of available test facilities, and the ban on protans was revoked in 2003.[94]

protans

All color blind individuals are banned from obtaining a driver's license in China and since 2016 in Russia (2012 for dichromats).[100]

[99]

– Ability to see colors, but inability to recognize colors.

Color agnosia

– Ability to see colors, but inability to name colors.

Color anomia

List of people with color blindness

Motion blindness

Tetrachromacy

at Curlie

Color blindness

Archived 4 October 2015 at the Wayback Machine

"A Glossary of Color Science."