Color blindness

Source: Wikipedia, the free encyclopedia.
(Redirected from
Color vision deficiency
)

Color blindness
Other namesColor vision deficiency, impaired color vision
mobile apps[1][2]
FrequencyRed–green: 8% males, 0.5% females (Northern European descent)[2]

Color blindness or color vision deficiency (CVD) is the decreased ability to

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]

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,

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]

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.

  • Normal sight
    Normal sight
  • Deuteranopic sight
    Deuteranopic sight
  • Protanopic sight
    Protanopic sight
  • Tritanopic sight
    Tritanopic sight
  • Monochromatic sight
    Monochromatic sight

Confusion colors

Confusion lines for the three types of dichromacy superimposed on CIEXYZ color space.

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.[8] 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:[9]

  • 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

Simulation of the normal (above) and dichromatic (below) perception of red and green apples

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 lack of standard positional clues makes this light difficult to interpret.

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 infamous inverted traffic light in Syracuse, NY

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

Irish American community.[10] However, the light has been criticized due to the potential hazard it poses for color blind drivers.[11]

Horizontal traffic light in Halifax, Nova Scotia, Canada

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.[citation needed] 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 not necessarily whether someone is color blind, but whether they can functionally distinguish these specific signal colors. Those who cannot pass this test are generally completely restricted from working on aircraft, ships or rail, for example.

Fashion

Color analysis is the analysis of color in its use in fashion, to determine personal color combinations that are most aesthetically pleasing.[12] Colors to combine can include clothing, accessories, makeup, hair color, skin color, eye color, etc. Color analysis involves many aesthetic and comparative color task that can be difficult for the color blind.

Art

Inability to distinguish color does not necessarily preclude the ability to become a celebrated artist. The 20th century expressionist painter

Charles Méryon became successful by concentrating on etching rather than painting after he was diagnosed as having a red–green deficiency.[14] Jin Kim's red–green color blindness did not stop him from becoming first an animator and later a character designer with Walt Disney Animation Studios.[15]

Advantages

Deuteranomals are better at distinguishing shades of khaki,[16] which may be advantageous when looking for predators, food, or camouflaged objects hidden among foliage.[17] Dichromats tend to learn to use texture and shape clues and so may be able to penetrate camouflage that has been designed to deceive individuals with normal color vision.[18][19]

Some tentative evidence finds that the color blind are better at penetrating certain color camouflages. Such findings may give an evolutionary reason for the high rate of red–green color blindness.[18] There is also a study suggesting that people with some types of color blindness can distinguish colors that people with normal color vision are not able to distinguish.[20] In World War II, color blind observers were used to penetrate camouflage.[21]

In the presence of chromatic noise, the color blind are more capable of seeing a luminous signal, as long as the chromatic noise appears

Ishihara plates) that are discernible to the color blind but unreadable to people with typical color vision.[citation needed
]

Digital design

snippet of colored cells in a table (foreground), surrounded in background showing how the image appears in color-blindness simulations.
Testing the colors of a web chart, (center), to ensure that no information is lost to the various forms of color blindness.

Color codes are useful tools for designers to convey information. The interpretation of this information requires users to perform a variety of Color Tasks, usually comparative but also sometimes connotative or denotative. However, these tasks are often problematic for the color blind when design of the color code has not followed best practices for accessibility.[23] For example, one of the most ubiquitous connotative color codes is the "red means bad and green means good" or similar systems, based on the classic signal light colors. However, this color coding will almost always be undifferentiable to deutans or protans, and therefore should be avoided or supplemented with a parallel connotative system (symbols, smileys, etc.).

Good practices to ensure design is accessible to the color blind include:

  • When possible (e.g. in simple video games or apps), allowing the user to choose their own colors is the most inclusive design practice.
  • Using other signals that are parallel to the color coding, such as patterns, shapes, size or order.[24] This not only helps the color blind, but also aids understanding by normally sighted people by providing them with multiple reinforcing cues.
  • Using brightness contrast (different shades) in addition to color contrast (different hues)
  • To achieve good contrast, conventional wisdom suggests converting a (digital) design to grayscale to ensure there is sufficient brightness contrast between colors. However, this does not account for the different perceptions of brightness to different varieties of color blindness, especially protan CVD, tritan CVD and monochromacy.
  • Viewing the design through a CVD Simulator to ensure the information carried by color is still sufficiently conveyed. At a minimum, the design should be tested for deutan CVD, the most common kind of color blindness.
  • Maximizing the area of colors (e.g. increase size, thickness or boldness of colored element) makes the color easier to identify. Color contrast improves as the angle the color subtends on the retina increases. This applies to all types of color vision.
  • Maximizing brightness (value) and saturation (chroma) of the colors to maximize color contrast.
  • Converting connotative tasks to comparative tasks by including a legend, even when the meaning is considered obvious (e.g. red means danger).
  • Avoiding denotative color tasks (color naming) when possible. Some denotative tasks can be converted to comparative tasks by depicting the actual color whenever the color name is mentioned; for example, colored typography in "purple",  purple  or "purple ()".
  • For denotative tasks (color naming), using the most common shades of colors. For example, green and yellow are colors of confusion in red–green CVD, but it is very common to mix forest green () with bright yellow (). Mistakes by the color blind increase drastically when uncommon shades are used, e.g. neon green () with dark yellow ().
  • For denotative tasks, using colors that are classically associated with a color name. For example, use "firetruck" red () instead of burgundy () to represent the word "red".

Unordered Information

Colors of board game pieces must be carefully chosen to be accessible to the color blind

A common task for designers is to select a subset of colors (qualitative colormap) that are as mutually differentiable as possible (salient). For example, player pieces in a board game should be as different as possible.

Classic advice suggests using Brewer palettes, but several of these are not actually accessible to the color blind.

Unfortunately, the colors with the greatest contrast to the red–green color blind tend to be colors of confusion to the blue–yellow color blind, and vice versa. However, since red–green is much more prevalent than blue–yellow CVD, design should[according to whom?] generally prioritize those users (deutans then protans).

Ordered Information

Three sequential colormaps that have been designed to be accessible to the color blind.

A common task for data visualization is to represent a color scale, or sequential colormap, often in the form of a

monotonic
and perceptually uniform to all forms of color vision.

Classification

These color charts show how different color blind people see compared to a person with normal color vision.[dubious ]

Much terminology has existed and does exist for the classification of color blindness, but the typical classification for color blindness follows the von Kries classifications,[26] 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.[27] Partial color blindness includes dichromacy and anomalous trichromacy, but is often clinically defined as mild, moderate or strong.

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

blue cone monochromacy).[28][29]

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.[29]

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:

  1. 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.
  2. 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 nm). People with this condition generally show nystagmus ("jiggling eyes"), photophobia (light sensitivity), reduced visual acuity, and myopia (nearsightedness).[30]
    Visual acuity usually falls to the 20/50 to 20/400 range.

Dichromacy

Dichromats can match any color they see with some mixture of just two primary colors (in contrast to those with normal sight (trichromats) who can distinguish three primary colors).[28] 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, but the severity ranges from almost dichromacy (strong) to almost normal trichromacy (mild).[31] 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.[32] 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.[33]

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.[34][35][dubious ] 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/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).

John Dalton
, who had red–green dichromacy. In some languages, daltonism is still used to describe red–green color blindness.

Illustration of the distribution of cone cells in the 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.

  • Protan (2% of males): Lacking, or possessing anomalous 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.[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.

  • Deutan (6% of males): Lacking, or possessing anomalous M-opsins 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.[40]

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.[41] Tritans have a neutral point at 571 nm (yellowish).[citation needed]

  • Tritan (< 0.01% of individuals): Lacking, or possessing anomalous S-opsins or short-wavelength sensitive cone cells. Tritans see short-wavelength colors (blue, indigo and spectral 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".[42]

  • Tetartan is the "fourth type" of color blindness, and a type of blue–yellow color blindness. However, its existence is hypothetical and given the molecular basis of human color vision, it is unlikely this type could exist.[citation needed]

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.

Cone system Red Green Blue N = normal
A = anomalous
N A N A N A
1 Normal vision Trichromacy Normal
2 Protanomaly Anomalous trichromacy Partial
color
blindness
Red–
green
3 Protanopia Dichromacy
4 Deuteranomaly Anomalous trichromacy
5 Deuteranopia Dichromacy
6 Tritanomaly Anomalous trichromacy Blue–
yellow
7 Tritanopia Dichromacy
8 Blue cone monochromacy Monochromacy Total color blindness
9 Achromatopsia
10 Tetrachromacy
(carrier theory)
Tetrachromacy 'Superior'
11

Causes

Color blindness is any deviation of color vision from normal

photons
and thereby convert light into chemical signals.

Color vision deficiencies can be classified as inherited or acquired.

Genetics

Color blindness is typically an inherited genetic disorder. The most common forms of color blindness are associated with the

Photopsin genes, but the mapping of the human genome has shown there are many causative mutations that do not directly affect the opsins. Mutations capable of causing color blindness originate from at least 19 different chromosomes and 56 different genes (as shown online at the Online Mendelian Inheritance in Man
[OMIM]).

Genetics of red–green color blindness

A chart showing likelihoods of genetic combinations and outcomes for red–green color blindness
Punnett squares for each combination of parents' color vision status giving probabilities of their offsprings' status; A superscript 'c' denotes a chromosome with an affected gene

By far the most common form of color blindness is congenital red–green color blindness (Daltonism), which includes protanopia/protanomaly and deuteranopia/deuteranomaly. These conditions are mediated by the OPN1LW and OPN1MW genes, respectively, both on the X chromosome. An 'affected' gene is either missing (as in Protanopia and Deuteranopia - Dichromacy) or is a chimeric gene (as in Protanomaly and Deuteranomaly).

Since the

alleles are recessive, color blindness specifically follows X-linked recessive inheritance
. Males have only one X chromosome (XY), and females have two (XX); Because the male only has one of each gene, if it is affected, the male will be color blind. Because a female has two alleles of each gene (one on each chromosome), if only one gene is affected, the dominant normal alleles will "override" the affected, recessive allele and the female will have normal color vision. However, if the female has two mutated alleles, she will still be color blind. This is why there is a disproportionate prevalence of color blindness, with ~8% of males exhibiting color blindness and ~0.5% of females.

Genetics of blue–yellow color blindness

Congenital blue–yellow color blindness is a much rarer form of color blindness including tritanopia/tritanomaly. These conditions are mediated by the OPN1SW gene on Chromosome 7 which encodes the S-opsin protein and follows autosomal dominant inheritance.[44] The cause of blue–yellow color blindness is not analogous to the cause of red–green color blindness, i.e. the peak sensitivity of the S-opsin does not shift to longer wavelengths. Rather, there are 6 known point mutations of OPN1SW that degrade the performance of the S-cones.[45] The OPN1SW gene is almost invariant in the human population. Congenital tritan defects are often progressive, with nearly normal trichromatic vision in childhood (e.g. mild tritanomaly) progressing to dichromacy (tritanopia) as the S-cones slowly die.[45] Tritanomaly and tritanopia are therefore different penetrance of the same disease, and some sources have argued that tritanomaly therefore be referred to as incomplete tritanopia.[44]

Other genetic causes

Several inherited diseases are known to cause color blindness, including

congenital or commence in childhood or adulthood. They can be static/stationary or progressive. Progressive diseases often involve deterioration of the retina and other parts of the eye, so often progress from color blindness to more severe visual impairments
, up to and including total blindness.

Non-genetic causes

Physical trauma can cause color blindness, either neurologically – brain trauma which produces swelling of the brain in the

ultraviolet light
exposure).

Color blindness may also present itself as a symptom of degenerative diseases of the eye, such as cataract and age-related macular degeneration, and as part of the retinal damage caused by diabetes. Vitamin A deficiency may also cause color blindness.[46]

Color blindness may be a

Viagra.[48] Hydroxychloroquine can also lead to hydroxychloroquine retinopathy, which includes various color defects.[49] Exposure to chemicals such as styrene[50] or organic solvents[51][52]
can also lead to color vision defects.

Simple colored filters can also create mild color vision deficiencies. John Dalton's original hypothesis for his deuteranopia was actually that the

vitreous humor
of his eye was discolored:

I was led to conjecture that one of the humours of my eye must be a transparent, but coloured, medium, so constituted as to absorb red and green rays principally... I suppose it must be the vitreous humor.

— John Dalton, Extraordinary facts relating to the vision of colours: with observations (1798)

An autopsy of his eye after his death in 1844 showed this to be definitively untrue,

lens
.

The opponent channels can also be affected by the prevalence of certain cones in the retinal mosaic. The cones are not equally prevalent and not evenly distributed in the retina. When the number of one of these cone types is significantly reduced, this can also lead to or contribute to a color vision deficiency. This is one of the causes of tritanomaly.

Some people are also unable to distinct between blue and green, which appears to be a combination of culture and exposure to UV-light.[54]

Diagnosis

Color vision test

An Ishihara test image as seen by subjects with normal color vision and by those with a variety of color deficiencies

The main method for diagnosing a color vision deficiency is in testing the color vision directly. The

Ishihara color test is the test most often used to detect red–green deficiencies and most often recognized by the public.[1] Some tests are clinical in nature, designed to be fast, simple, and effective at identifying broad categories of color blindness. Others focus on precision and are generally available only in academic settings.[55]

A Farnsworth D-15 test
  • Arrangement tests can be used as screening or diagnostic tools. The Farnsworth–Munsell 100 hue test is very sensitive, but the Farnsworth D-15 is a simplified version used specifically for screening for CVD. In either case, the subject is asked to arrange a set of colored caps or chips to form a gradual transition of color between two anchor caps.[56]
  • Anomaloscopes are typically designed to detect red–green deficiencies and are based on the Rayleigh match, which compares a mixture of red and green light in variable proportions to a fixed spectral yellow of variable luminosity. The subject must change the two variables until the colors appear to match. They are expensive and require expertise to administer, so they are generally only used in academic settings.

Genetic testing

While genetic testing cannot directly evaluate a subject's color vision (phenotype), most congenital color vision deficiencies are well-correlated with genotype. Therefore, the genotype can be directly evaluated and used to predict the phenotype. This is especially useful for progressive forms that do not have a strongly color deficient phenotype at a young age. However, it can also be used to sequence the L- and M-Opsins on the X-chromosome, since the most common alleles of these two genes are known and have even been related to exact spectral sensitivities and peak wavelengths. A subject's color vision can therefore be classified through genetic testing,[57] but this is just a prediction of the phenotype, since color vision can be affected by countless non-genetic factors such as your cone mosaic.

Management

Despite much recent improvement in gene therapy for color blindness, there is currently no FDA approved treatment for any form of CVD, and otherwise no cure for CVD currently exists. Management of the condition by using lenses to alleviate symptoms or smartphone apps to aid with daily tasks is possible.

Lenses

There are three kinds of lenses that an individual can wear that can increase their accuracy in some color related tasks (although none of these will "fix" color blindness or grant the wearer normal color vision):

  • A red-tint contact lens worn over the non-dominant eye will leverage binocular disparity 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.[58] A case history using the X-Chrom lens for a rod monochromat is reported[59] and an X-Chrom manual is online.[60]
  • 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 color vision tests, though this is typically not allowed.[61]
  • Glasses with a
    notch filter (e.g. EnChroma glasses) filter a narrow band of light that excites both the L and M cones (yellow–green wavelengths).[62] 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.[63]

Aids

Many mobile and computer applications have been developed to aid color blind individuals in completing color tasks:

  • Some applications (e.g. color pickers) can identify the name (or coordinates within a color space) of a color on screen or the color of an object by using the device's camera.
  • Some applications will make images easier to interpret by the color blind by enhancing color contrast in natural images and/or information graphics. These methods are generally called daltonization algorithms.[64]
  • Some applications can simulate color blindness by applying a filter to an image or screen that reduces the gamut of an image to that of a specific type of color blindness. While they do not directly help color blind people, they allow those with normal color vision to understand how the color blind see the world. Their use can help improve inclusive design by allowing designers to simulate their own images to ensure they are accessible to the color blind.[65]

In 2003, a cybernetic device called

TED Conference, Harbisson explained how he could now perceive colors outside the ability of human vision.[67]

Epidemiology

Rates of color blindness[clarification needed][citation needed]
Males Females
Dichromacy 2.4% 0.03%
Protanopia 1.3% 0.02%
Deuteranopia 1.2% 0.01%
Tritanopia 0.008% 0.008%
Anomalous trichromacy 6.3% 0.37%
Protanomaly 1.3% 0.02%
Deuteranomaly 5.0% 0.35%
Tritanomaly 0.0001% 0.0001%

Color blindness affects a large number of individuals, with protans and deutans being the most common types.[36] In individuals with Northern European ancestry, as many as 8 percent of men and 0.4 percent of women experience congenital color deficiency.[68] Interestingly, even Dalton's very first paper already arrived upon this 8% number:[69]

...it is remarkable that, out of 25 pupils I once had, to whom I explained this subject, 2 were found to agree with me...

— John Dalton, Extraordinary facts relating to the vision of colours: with observations (1798)

History

An 1895 illustration of normal vision and various kinds of color blindness.

During the 17th and 18th century, several philosophers hypothesized that not all individuals perceived colors in the same way:[70]

...there is no reason to suppose a perfect resemblance in the disposition of the Optic Nerve in all Men, since there is an infinite variety in every thing in Nature, and chiefly in those that are Material, 'tis therefore very probable that all Men see not the same Colours in the same Objects.

— Nicolas Malebranche, The search after truth (1674) [71]

In the power of conceiving colors, too, there are striking differences among individuals: and, indeed, I am inclined to suspect, that, in the greater number of instances, the supposed defects of sight in this respect ought to be ascribed rather to a defect in the power of conception.

— Dugald Stewart, Elements of the philosophy of the human mind (1792) [72]

The phenomenon only came to be scientifically studied in 1794, when English chemist John Dalton gave the first account of color blindness in a paper to the Manchester Literary and Philosophical Society, which was published in 1798 as Extraordinary Facts relating to the Vision of Colours: With Observations.[73][69] Genetic analysis of Dalton's preserved eyeball confirmed him as having deuteranopia in 1995, some 150 years after his death.[74]

Influenced by Dalton, German writer

J. W. von Goethe studied color vision abnormalities in 1798 by asking two young subjects to match pairs of colors.[75]

In 1875, the

Alarik Frithiof Holmgren, a physiologist, investigated and concluded that the color blindness of the engineer (who had died) had caused the crash. Professor Holmgren then created the first test for color vision using multicolored skeins of wool to detect color blindness and thereby exclude the color blind from jobs in the transportation industry requiring color vision to interpret safety signals.[76] However, there is a claim that there is no firm evidence that color deficiency did cause the collision, or that it might have not been the sole cause.[77]

In 1920, Frederick William Edridge-Green devised an alternative theory of color vision and color blindness based on Newton's classification of 7 fundamental colors (ROYGBIV). Edridge-Green classified color vision based on how many distinct colors a subject could see in the spectrum. Normal subjects were termed hexachromic as they could not discern Indigo. Subjects with superior color vision, who could discern indigo, were heptachromic. The color blind were therefore dichromic (equivalent to dichromacy) or tri-, tetra- or pentachromic (anomalous trichromacy).[78][79]

Rights

In the United States, under federal anti-discrimination laws such as the Americans with Disabilities Act, color vision deficiencies have not been found to constitute a disability that triggers protection from workplace discrimination.

A Brazilian court ruled that the color blind are protected by the Inter-American Convention on the Elimination of All Forms of Discrimination against Person with Disabilities.[80][81][82] At trial, it was decided that the carriers of color blindness have a right of access to wider knowledge, or the full enjoyment of their human condition.[citation needed]

Occupations

Color blindness may make it difficult or impossible for a person to engage in certain activities. Persons with color blindness may be legally or practically barred from occupations in which color perception is an essential part of the job (e.g., mixing paint colors), or in which color perception is important for safety (e.g., operating vehicles in response to color-coded signals). This occupational safety principle originates from the aftermath of the 1875

Alarik Frithiof Holmgren blamed on the color blindness of the engineer and created the first occupational screening test (Holmgren's wool test) against the color blind.[76]

...I consider that to [Holmgren] above all others do we owe the present and future control of color-blindness on land and sea, by which life and property are safer, and the risks of travelling less.

— Benjamin Joy Jeffries, Color-blindness: Its Danger & Its Detection (1879)

Color vision is important for occupations using telephone or computer networking cabling, as the individual wires inside the cables are color-coded using green, orange, brown, blue and white colors.[83] Electronic wiring, transformers, resistors, and capacitors are color-coded as well, using black, brown, red, orange, yellow, green, blue, violet, gray, white, silver, and gold.[84]

Participation, officiating and viewing sporting events can be impacted by color blindness. Professional football players Thomas Delaney and Fabio Carvalho have discussed the difficulties when color clashes occur, and research undertaken by FIFA has shown that enjoyment and player progression can be hampered by issues distinguishing the difference between the pitch and training objects or field markings.[85] Snooker World Champions Mark Williams and Peter Ebdon sometimes need to ask the referee for help distinguishing between the red and brown balls due to their color blindness. Both have played foul shots on notable occasions by potting the wrong ball.[86][87][88]

Driving

Red–green color blindness can make it difficult to drive, primarily due to the inability to differentiate red–amber–green

traffic lights. Protans are further disadvantaged due to the darkened perception of reds, which can make it more difficult to quickly recognize brake lights.[89] In response, some countries have refused to grant driver's licenses
to individuals with color blindness:

Piloting aircraft

Although many aspects of aviation depend on color coding, only a few of them are critical enough to be interfered with by some milder types of color blindness. Some examples include color-gun signaling of aircraft that have lost radio communication, color-coded glide-path indications on runways, and the like. Some jurisdictions restrict the issuance of pilot credentials to persons with color blindness for this reason. Restrictions may be partial, allowing color-blind persons to obtain certification but with restrictions, or total, in which case color-blind persons are not permitted to obtain piloting credentials at all.[96]

In the United States, the Federal Aviation Administration requires that pilots be tested for normal color vision as part of their medical clearance in order to obtain the required medical certificate, a prerequisite to obtaining a pilot's certification. If testing reveals color blindness, the applicant may be issued a license with restrictions, such as no night flying and no flying by color signals—such a restriction effectively prevents a pilot from holding certain flying occupations, such as that of an airline pilot, although commercial pilot certification is still possible, and there are a few flying occupations that do not require night flight and thus are still available to those with restrictions due to color blindness (e.g., agricultural aviation). The government allows several types of tests, including medical standard tests (e.g., the Ishihara, Dvorine, and others) and specialized tests oriented specifically to the needs of aviation. If an applicant fails the standard tests, they will receive a restriction on their medical certificate that states: "Not valid for night flying or by color signal control". They may apply to the FAA to take a specialized test, administered by the FAA. Typically, this test is the "color vision light gun test". For this test an FAA inspector will meet the pilot at an airport with an operating control tower. The color signal light gun will be shone at the pilot from the tower, and they must identify the color. If they pass they may be issued a waiver, which states that the color vision test is no longer required during medical examinations. They will then receive a new medical certificate with the restriction removed. This was once a Statement of Demonstrated Ability (SODA), but the SODA was dropped, and converted to a simple waiver (letter) early in the 2000s.[97]

Research published in 2009 carried out by the

Civil Aviation Authority and the U.S. Federal Aviation Administration, has established a more accurate assessment of color deficiencies in pilot applicants' red/green and yellow–blue color range which could lead to a 35% reduction in the number of prospective pilots who fail to meet the minimum medical threshold.[98]

See also

References

  1. ^
    PMID 9581449
    .
  2. ^ a b c d e f g h i j k l m n o p "Facts About Color Blindness". NEI. February 2015. Archived from the original on 28 July 2016. Retrieved 29 July 2016.
  3. ^ "Colour vision deficiency (colour blindness)". nhs.uk. 18 October 2017. Retrieved 17 March 2022.
  4. S2CID 53721875
    .
  5. ^ "OSHA does not have requirements for normal color vision. | Occupational Safety and Health Administration". www.osha.gov. Retrieved 6 May 2019.
  6. PMID 11274694
    .
  7. .
  8. .
  9. .
  10. ^ "New documentary uncovers the Irish links to America's Tipperary Hill". TheJournal.ie. 6 November 2016. Archived from the original on 15 August 2017. Retrieved 15 August 2017.
  11. ^ Zhang, Sarah (17 March 2014). "The Story Behind Syracuse's Upside-Down Traffic Light". Gizmodo. Archived from the original on 16 September 2014.
  12. ^ "What is Color Analysis?". London Image Institute. 1 January 2022. Retrieved 21 February 2024.
  13. S2CID 21676461
    .
  14. ^ Anon. "Charles Meryon". Art Encyclopedia. The Concise Grove Dictionary of Art. Oxford University Press. Archived from the original on 25 November 2010. Retrieved 7 January 2010.
  15. ^ Lee Hw (15 May 2011). "Dreams come true, Disney style". The Korea Times. Retrieved 25 November 2019.
  16. .
  17. .
  18. ^ .
  19. .
  20. .
  21. ^ "Colour blindness not all it seems". BBC News. 6 December 2015. Archived from the original on 23 June 2016. Retrieved 21 June 2016.
  22. PMID 33087826
    .
  23. .
  24. ^ Caprette H. "14 Avoiding the Use of Color Alone to Convey Meaning and Algorithms That Help". Best Practices in Accessible Online Design. Pressbooks @ MSL.
  25. ^
    PMID 30067751
    .
  26. ^ von Kries J (1897). "Ueber Farbensysteme". Zeitschrift für Psychologie Physiologie Sinnesorg. 13: 241–324.
  27. ^ Spring KR, Parry-Hill MJ, Fellers TJ, Davidson MW. "Human Vision and Color Perception". Florida State University. Archived from the original on 27 August 2007. Retrieved 5 April 2007.
  28. ^ a b "Types of Colour Blindness". Colour Blind Awareness. Archived from the original on 29 May 2014.
  29. ^ a b Blom JD (2009). A Dictionary of Hallucinations. Springer. p. 4. from the original on 27 December 2016.
  30. .
  31. .
  32. .
  33. .
  34. ^ Hoffman PS. "Accommodating Color Blindness" (PDF). Archived from the original (PDF) on 15 May 2008. Retrieved 1 July 2009.
  35. ^ Neitz ME. "Severity of Colorblindness Varies". Medical College of Wisconsin. Archived from the original on 5 February 2007. Retrieved 5 April 2007.
  36. ^ a b Wong B (June 2011). "Color blindness". Nature Methods. 8 (6): 441.
    S2CID 36690778
    .
  37. .
  38. .
  39. .
  40. ^ MacAdam DL, Judd DB, eds. (1979). Contributions to color science. NBS. p. 584.
  41. ^ 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.
  42. ^ "Disease-causing Mutations and protein structure". UCL Biochemistry BSM Group. Archived from the original on 1 May 2005. Retrieved 2 April 2007.
  43. ^ "Acquired colour vision defects". colourblindawareness.org. Archived from the original on 16 December 2014.
  44. ^ a b Sharpe LT, Stockman A, Jägle H, Nathans J (1999). "Opsin genes, cone photopigments, color vision, and color blindness.". Color vision: From genes to perception (PDF). p. 351. True cases of tritanomaly, as distinct from partial or incomplete tritanopia, have never been satisfactorily documented. Although the separate existence of tritanopia and tritanomaly, with different modes of inheritance, has been postulated, it now seems more likely that tritanomaly does not exist, but rather has been mistaken for incomplete tritanopia.
  45. ^
    S2CID 226504635
    .
  46. ^ Leikin JB, Lipsky MS, eds. (2003). Complete Medical Encyclopedia. Random House Reference (First ed.). New York, NY: Random House, for the American Medical Association. p. 388. . Retrieved 1 December 2011 – via archive.org.
  47. ^ "Myambutol (Ethambutol)". RxList.com. drug information. Archived from the original on 8 July 2014. Retrieved 24 May 2014. Description, user reviews, drug side effects, interactions–prescribing information
  48. ^ "VIAGRA (SILDENAFIL CITRATE) DRUG". RxList.com. drug information. Retrieved 3 June 2022. Description, user reviews, drug side effects, interactions–prescribing information
  49. ^ Fraunfelder FT, Fraunfelder FW, Chambers WA (2014). Drug-Induced Ocular Side Effects: Clinical ocular toxicology e‑book. Elsevier Health Sciences. p. 79. .
  50. ^ Choi AR, Braun JM, Papandonatos GD, Greenberg PB (November 2017). "Occupational styrene exposure and acquired dyschromatopsia: A systematic review and meta-analysis". American Journal of Industrial Medicine. 60 (11): 930–946.
    PMID 28836685
    .
  51. ^ Betancur-Sánchez AM, Vásquez-Trespalacios EM, Sardi-Correa C (January 2017). "Impaired colour vision in workers exposed to organic solvents: A systematic review". Archivos de la Sociedad Espanola de Oftalmologia. 92 (1): 12–18.
    PMID 27422480
    .
  52. ^ Dick F (March 2006). "Solvent neurotoxicity". Occupational and Environmental Medicine. 63 (3): 221–6, 179.
    PMID 16497867
    .
  53. .
  54. ^ Environment and culture shape both the colour lexicon and the genetics of colour perception
  55. PMID 15192692
    .
  56. .
  57. ^ Reference GH. "Color vision deficiency". Genetics Home Reference. Retrieved 6 May 2019.
  58. PMID 6971497
    .
  59. .
  60. ^ An X-Chrom manual Archived 2015-04-12 at the Wayback Machine. Artoptical.com. Retrieved on 2016-12-10.
  61. PMID 313209
    . Retrieved 30 September 2022.
  62. ^ Zhou L. "A Scientist Accidentally Developed Sunglasses That Could Correct Color Blindness". Smithsonian. Retrieved 6 January 2018.
  63. S2CID 53721875
    .
  64. .
  65. ^ "Colour Blindness: Experience it". Colour Blind Awareness. Retrieved 11 December 2019.
  66. ^ "I listen to color" Archived 2012-08-12 at the Wayback Machine, Neil Harbisson at TED Global, 27 June 2012.
  67. .
  68. ^ a b Dalton J (1798). "Extraordinary Facts relating to the Vision of Colours: With Observations". Manchester Literary and Philosophical Society. Memoirs. 5 (1). England, Manchester: 28–45.
  69. . Retrieved 14 April 2022.
  70. ^ Malebranche N (1712) [1674]. Malebranch's search after truth, or, A treatise of the nature of the humane mind and of its management for avoiding error in the sciences : vol I: done out of French from the last edition. p. 88. Retrieved 14 April 2022.
  71. ^ Stewart D (1792). Elements of the philosophy of the human mind (1 ed.). p. 80. Retrieved 14 April 2022.
  72. ^ Lanthony 2018, p. 14.
  73. S2CID 6764146
    .
  74. ^ Lanthony 2018, pp. 25–26.
  75. ^
    S2CID 41486427
    .
  76. .
  77. .
  78. .
  79. ^ "Full text of the decision of the court – in Portuguese language". Archived from the original on 14 July 2012. Retrieved 9 March 2012.
  80. ^ "Decree issued by president of a republic ratifying Legislative Decree No. 198, of june 13, which approved the Inter-American Convention AG/RES. 1608 – in Portuguese language". Archived from the original on 25 March 2012. Retrieved 9 March 2012.
  81. ^ "Inter-American Convention on the Elimination of All Forms of Discrimination against Person with Disabilities". Archived from the original on 16 April 2013. Retrieved 9 March 2012.
  82. ]
  83. ]
  84. ^ "Football players shocked when experiencing Colour Blindness". Tacbis.
  85. ^ "Billiard Index: Mark Williams MBE player profile". Billiard Index. Archived from the original on 8 July 2008. Retrieved 15 November 2023.
  86. ^ "Hawkins on Top Down Under". World Snooker Tour. 15 July 2012. Archived from the original on 17 October 2023. Retrieved 15 November 2023.
  87. ^ "Rueful Ebdon mistakes brown for red". BBC Sport. 13 October 2008. Archived from the original on 4 May 2012. Retrieved 15 November 2023.
  88. ^
    S2CID 26368283
    .
  89. ^ "ORDIN 87 03/02/2003 – Portal Legislativ". PORTAL LEGISLATIV (in Romanian). Ministerul Justiției. Retrieved 31 December 2021.
  90. ^ "ORDIN 87 03/02/2003 – Portal Legislativ". PORTAL LEGISLATIV (in Romanian). Ministerul Justiției. Retrieved 31 December 2021.
  91. ^ Corlăţean T. "Discrimination against Romanians with genetic chromatic deficiencies". Retrieved 31 December 2021.
  92. ^ "Mild to medium colour blind people can now obtain driver's license". The Times of India. Press Trust of India. 26 June 2020. Retrieved 1 June 2022.
  93. ^ Lu F. "Some of us see the world in a different light". Shine. Retrieved 1 June 2022.
  94. ^ "Do color blindmen a driver's license. Color blindmen allowed to drive cars". Rozavet. Retrieved 1 June 2022.
  95. ^ "Answers for Pilots: Color vision". January 2012.
  96. ^ "Aerospace Medical Dispositions – Color vision". Archived from the original on 12 May 2009. Retrieved 11 April 2009.
  97. ^ Warburton S (29 May 2009). "Colour-blindness research could clear more pilots to fly: UK CAA". Air transport. Reed Business Information. Archived from the original on 2 June 2009. Retrieved 29 October 2009.

Further reading

External links