Color vision test

Last updated

A color vision test is used for measuring color vision against a standard. These tests are most often used to diagnose color vision deficiencies (color blindness), though several of the standards are designed to categorize normal color vision into sub-levels. With the large prevalence of color vision deficiencies (8% of males) and the wide range of professions that restrict hiring the colorblind for safety or aesthetic reasons, clinical color vision standards must be designed to be fast and simple to implement. Color vision standards for academic use trade speed and simplicity for accuracy and precision.

Contents

Applications

Color vision standards are used to evaluate the color vision of a subject. They are most commonly applied to job applicants during pre-job screening. The evaluation may be to select against the color vision deficient for roles where basic color vision is required, or to select for individuals with superior color vision for roles where recognition of subtle color difference is required. [1]

Alterations to color vision are common symptoms of toxicity and eye health, so color vision standards can also be used to detect conditions of the eye or brain or to track the recovery from these conditions. [1]

Pseudoisochromatic plates

An Ishihara test image as seen by subjects with normal color vision and by those with a variety of color deficiencies Ishihara compare 1.jpg
An Ishihara test image as seen by subjects with normal color vision and by those with a variety of color deficiencies

A pseudoisochromatic plate (from Greek pseudo, meaning "false", iso, meaning "same" and chromo, meaning "color"), often abbreviated as PIP, is a style of standard exemplified by the Ishihara test, generally used for screening of color vision defects. [2]

A figure (usually one or more numerals) is embedded in the plate as a number of spots surrounded by spots of a slightly different color. The figure can be seen with normal color vision, but not with a particular color defect. The figure and background colors must be carefully chosen to appear isochromatic to a color deficient individual, but not an individual with normal color vision. [2]

Pseudoisochromatic Plates are used as screening tools because they are cheap, fast and simple, but they do not provide precise diagnosis of CVD, and are often followed with another test if a user fails the PIP standard. [3]

Ishihara plates

Ishihara plates hide Arabic numerals within PIPs. They are the test most often used to screen for red–green color deficiencies and most often recognized by the public. [4] However, this can be attributed more to its ease of application, and less to do with its precision. [2]

The basic Ishihara test may not be useful in diagnosing young, preliterate children, who can't read the numerals, but larger editions contain plates that showcase a simple path to be traced with a finger, rather than numerals. [5]

HRR plates

The second most common PIP color vision standard is the HRR color test (developed by Hardy, Rand, and Rittler), which solves many of the criticisms of the Ishihara test. For example, it detects blue-yellow color blindness, is less susceptible to memorization and uses shapes, so it is accessible to the illiterate and young children. [2]

Arrangement tests

A Farnsworth-Munsell 100 Hue Test Farnsworth-Munsell Hue Color Vision Test, Material and Finishing Laboratory.jpg
A Farnsworth–Munsell 100 Hue Test
A Farnsworth D-15 test Huetestfmd15-2.jpg
A Farnsworth D-15 test

Arrangement-style color vision standards comprise a spectrum of colors that must be arranged in an array to minimize the difference between adjacent colors. An error score is calculated from incorrectly positioned colors. Lower error scores denote better color vision. Typically, the subject is asked to arrange a set of colored caps or chips between two anchor caps. [6]

The Farnsworth–Munsell 100 hue test comprises 4 separate color arrays, each representing 20 arrangeable caps and 2 anchor caps. This gives a total of 88 colors, contrary to the standard's name. [7] The standard is sensitive enough that it not only can detect color blindness, but also categorize normal color vision into "low", "average" and "superior" levels based on their error score. [7] It is usually not used for the detection of CVD.

The Farnsworth D-15 is simpler, comprising a single array, which itself comprises 1 end cap and 15 arrangeable caps. [7] It is primarily used for occupational screening of CVD and is the standard of choice in most US/Canadian Police Forces (after screening with Ishihara). [8] About 50% of people who fail the Ishihara are able to pass the D15. [9]

Lanterns

Lanterns project small colored lights to a subject, who is required to identify the color of the lights. The colors are usually restricted to those of typical signal lights, i.e. red, green and yellow, though some lanterns may project other colors. The main signal light colors also happen to be colors of confusion for red-green CVD.

Lanterns are usually used for occupational screening as they are more closely related to the actual safety-related color tasks required in those occupations. For example, the Farnsworth Lantern Test is used extensively by the United States Armed Forces and FAA. [10] This test allows about 30% of individuals who fail the ishihara plates (generally those with mild CVD) to pass. [11]

Anomaloscopes

Anomaloscope using a Rayleigh Match Rayleigh Match Anomaloscope.png
Anomaloscope using a Rayleigh Match

Anomaloscopes are very expensive and require expertise to administer, so are generally only used in academic settings. However, they are very precise, being able to diagnose the type and severity of color blindness with high confidence. [12] An anomaloscope designed to detect red–green color blindness is based on the Rayleigh equation, 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. The values of the variables at match (and the deviation from the variables of a color normal subject) are used to diagnose the type and severity of colorblindness. For example, deutans will put too much green in the mixture and protans will put too much red in the mixture. [13]

Digital tests

The graduation of color vision tests to the digital space offers several advantages, but is not trivial. Even if the digital tests mimic a traditional test, the digital version must be requalified or validated and every screen it is viewed on must be well-calibrated. Freely available web-based tests suffer from a lack of validation and typical viewing on uncalibrated screens. However, when well controlled, digital tests offer several significant advantages over their analog counterparts:

Validated digital tests used for occupational screening include:

An example of a digital, mobile, non-validated test is the Android application "Color Blind Check".

Related Research Articles

<span class="mw-page-title-main">Color code</span> System for displaying information by using different colors

A color code is a system for encoding and representing non-color information with colors to facilitate communication. This information tends to be categorical though may also be sequential.

<span class="mw-page-title-main">Color blindness</span> Decreased ability to see color or color differences

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, 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, 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.

<span class="mw-page-title-main">Ishihara test</span> Color perception test

The Ishihara test is a color vision test for detection of red-green color deficiencies. It was named after its designer, Shinobu Ishihara, a professor at the University of Tokyo, who first published his tests in 1917.

<span class="mw-page-title-main">Munsell color system</span> Color space

In colorimetry, the Munsell color system is a color space that specifies colors based on three properties of color: hue, chroma, and value (lightness). It was created by Albert H. Munsell in the first decade of the 20th century and adopted by the United States Department of Agriculture (USDA) as the official color system for soil research in the 1930s.

Achromatopsia, also known as Rod monochromacy, is a medical syndrome that exhibits symptoms relating to five conditions, most notably monochromacy. Historically, the name referred to monochromacy in general, but now typically refers only to an autosomal recessive congenital color vision condition. The term is also used to describe cerebral achromatopsia, though monochromacy is usually the only common symptom. The conditions include: monochromatic color blindness, poor visual acuity, and day-blindness. The syndrome is also present in an incomplete form that exhibits milder symptoms, including residual color vision. Achromatopsia is estimated to affect 1 in 30,000 live births worldwide.

Dichromacy is the state of having two types of functioning photoreceptors, called cone cells, in the eyes. Organisms with dichromacy are called dichromats. Dichromats require only two primary colors to be able to represent their visible gamut. By comparison, trichromats need three primary colors, and tetrachromats need four. Likewise, every color in a dichromat's gamut can be evoked with monochromatic light. By comparison, every color in a trichromat's gamut can be evoked with a combination of monochromatic light and white light.

<span class="mw-page-title-main">Shinobu Ishihara</span> Japanese ophthalmologist (1879–1963)

Shinobu Ishihara was a Japanese ophthalmologist who created the Ishihara color test to detect colour blindness. He was an army surgeon.

<span class="mw-page-title-main">Cerebral achromatopsia</span> Medical condition

Cerebral achromatopsia is a type of color blindness caused by damage to the cerebral cortex of the brain, rather than abnormalities in the cells of the eye's retina. It is often confused with congenital achromatopsia but underlying physiological deficits of the disorders are completely distinct. A similar, but distinct, deficit called color agnosia exists in which a person has intact color perception but has deficits in color recognition, such as knowing which color they are looking at.

An anomaloscope is an instrument and color vision test, often used to quantify and characterize color blindness. They are expensive and require specialized knowledge to operate, but are viewed as the gold standard for color vision standards. As a result, they are normally used for academic studies, rather than job pre-screening. They are also used to validate other color vision standards with regards to classification of color vision defects.

<span class="mw-page-title-main">Lightness</span> Property of a color

Lightness is a visual perception of the luminance of an object. It is often judged relative to a similarly lit object. In colorimetry and color appearance models, lightness is a prediction of how an illuminated color will appear to a standard observer. While luminance is a linear measurement of light, lightness is a linear prediction of the human perception of that light.

<span class="mw-page-title-main">Jakob Stilling</span> German ophthalmologist

Jakob Stilling was a German ophthalmologist from Kassel.

The Farnsworth Lantern Test, or FALANT, is a color vision test originally developed specifically to screen sailors for tasks requiring color vision, such as identifying signal lights at night. It screens for red-green deficiencies, but not the much rarer blue color deficiency.

Gene therapy for color blindness is an experimental gene therapy of the human retina aiming to grant typical trichromatic color vision to individuals with congenital color blindness by introducing typical alleles for opsin genes. Animal testing for gene therapy began in 2007 with a 2009 breakthrough in squirrel monkeys suggesting an imminent gene therapy in humans. While the research into gene therapy for red-green colorblindness has lagged since then, successful human trials are ongoing for achromatopsia. Congenital color vision deficiency affects upwards of 200 million people in the world, which represents a large demand for this gene therapy.

<span class="mw-page-title-main">Unique hues</span> Pure blue, green, yellow or red hues that cannot be described as a mixture of other hues

Unique hue is a term used in perceptual psychology of color vision and generally applied to the purest hues of blue, green, yellow and red. The proponents of the opponent process theory believe that these hues cannot be described as a mixture of other hues, and are therefore pure, whereas all other hues are composite. The neural correlate of the unique hues are approximated by the extremes of the opponent channels in opponent process theory. In this context, unique hues are sometimes described as "psychological primaries" as they can be considered analogous to the primary colors of trichromatic color theory.

<span class="mw-page-title-main">Farnsworth–Munsell 100 hue test</span> Test of the human visual system

The Farnsworth–Munsell 100 Hue Color Vision test is a color vision test often used to test for color blindness. The system was developed by Dean Farnsworth in the 1940s and it tests the ability to isolate and arrange minute differences in various color targets with constant value and chroma that cover all the visual hues described by the Munsell color system. There are several variations of the test, one featuring 100 color hues and one featuring 15 color hues. Originally taken in an analog environment with physical hue tiles, the test is now taken from computer consoles. An accurate quantification of color vision accuracy is particularly important to designers, photographers and colorists, who all rely on accurate color vision to produce quality content.

<span class="mw-page-title-main">EnChroma</span> Eyeglasses marketed to color-blind people

EnChroma lenses are specialized glasses designed to address symptoms of red-green color blindness. Studies have shown that these lenses can alter the perception of colors that were already perceived, but they do not restore normal color vision.

The City University test is a color vision test used to detect color vision deficiency. The commonly used Ishihara test is used to detect mainly congenital red-green color blindness, but its usefulness is limited in detecting acquired color vision deficiencies.

<span class="mw-page-title-main">Color blind glasses</span> Light filters to alleviate color blindness

Color blind glasses or color correcting lenses are light filters, usually in the form of glasses or contact lenses, that attempt to alleviate color blindness, by bringing deficient color vision closer to normal color vision or to make certain color tasks easier to accomplish. Despite its viral status, the academic literature is generally skeptical of the efficacy of color correcting lenses.

<span class="mw-page-title-main">Color task</span> Task that involves the recognition of color

Color tasks are tasks that involve the recognition of colors. Color tasks can be classified according to how the color is interpreted. Cole describes four categories of color tasks:

<span class="mw-page-title-main">Congenital red–green color blindness</span> Most common genetic condition leading to color blindness

Congenital red–green color blindness is an inherited condition that is the root cause of the majority of cases of color blindness. It has no significant symptoms aside from its minor to moderate effect on color vision. It is caused by variation in the functionality of the red and/or green opsin proteins, which are the photosensitive pigment in the cone cells of the retina, which mediate color vision. Males are more likely to inherit red–green color blindness than females, because the genes for the relevant opsins are on the X chromosome. Screening for congenital red–green color blindness is typically performed with the Ishihara or similar color vision test. There is no cure for color blindness.

References

  1. 1 2 POKORNY, J; COLLINS, B; HOWETT, G (1981). PROCEDURES FOR TESTING COLOR VISION. NATIONAL RESEARCH COUNCIL.
  2. 1 2 3 4 Cole BL, Lian KY, Lakkis C (March 2006). "The new Richmond HRR pseudoisochromatic test for colour vision is better than the Ishihara test". Clinical & Experimental Optometry. 89 (2): 73–80. doi: 10.1111/j.1444-0938.2006.00015.x . PMID   16494609. S2CID   40118817.
  3. French A, Rose K, Cornell E, Thompson K (2008). "The evolution of colour vision testing" (PDF). Australian Orthoptic Journal. 40 (2): 7–15.
  4. Gordon N (March 1998). "Colour blindness". Public Health. 112 (2): 81–4. doi:10.1038/sj.ph.1900446. PMID   9581449.
  5. Ishihara, Shinobu (1972). Tests for Colour-Blindness (PDF). Kanehara Shuppan. Archived from the original (PDF) on 8 December 2020. Retrieved 17 June 2020.
  6. Kinnear PR, Sahraie A (December 2002). "New Farnsworth–Munsell 100 hue test norms of normal observers for each year of age 5–22 and for age decades 30–70". The British Journal of Ophthalmology. 86 (12): 1408–11. doi:10.1136/bjo.86.12.1408. PMC   1771429 . PMID   12446376.
  7. 1 2 3 Farnsworth, Dean (1943). "The Farnsworth–Munsell 100-Hue and Dichotomous Tests for Color Vision". Journal of the Optical Society of America. 33 (10): 568–574. Bibcode:1943JOSA...33..568F. doi:10.1364/josa.33.000568.
  8. Eggertson, Curran (12 August 2022). "Can cops be colorblind?". Chromaphobe. Retrieved 10 September 2022.
  9. Birch, Jennifer (June 2008). "Pass rates for the Farnsworth D15 colour vision test". Ophthalmic and Physiological Optics. 28 (3): 259–264. doi:10.1111/j.1475-1313.2008.00566.x. PMID   18426425. S2CID   26064694.
  10. "Guide for Aviation Medical Examiners: Aerospace Medical Dispositions Item 52. Color Vision". Federal Aviation Administration. Retrieved 10 September 2022.
  11. Cole, Barry L; Maddocks, Jennifer D (1998-11-01). "Can clinical colour vision tests be used to predict the results of the Farnsworth lantern test?". Vision Research. 38 (21): 3483–3485. doi:10.1016/S0042-6989(98)00119-9. ISSN   0042-6989. PMID   9893869. S2CID   33600297.
  12. Nagel, WA (1907). "Zwei Apparate für die Augenärzliche Funktionsprüfung: Adaptometer und kleines Spektralphotometer (Anomaloskop)". Zeitschrift für Augenheilkunde. 17: 201–222.
  13. Fulton, James T. "Detailed Interpretation of the Nagel Anomaloscope" . Retrieved 10 September 2022.
  14. 1 2 Hasrod, Nabeela; Rubin, Alan (26 March 2015). "Colour vision: A review of the Cambridge Colour Test and other colour testing methods". African Vision and Eye Health. 74 (1): 7 pages. doi: 10.4102/aveh.v74i1.23 .
  15. Mollon, J D; Regan, B C (2000). Cambridge Color Test Handbook.
  16. "A new web-based colour vision test". City, University of London. Retrieved 30 September 2022.
  17. Linhares, João M. M.; João, Catarina A. R.; Silva, Eva D. G.; de Almeida, Vasco M. N.; Santos, Jorge L. A.; Álvaro, Leticia; Nascimento, Sérgio M. C. (1 March 2016). "Assessing the effects of dynamic luminance contrast noise masking on a color discrimination task". Journal of the Optical Society of America A. 33 (3): A178-83. Bibcode:2016JOSAA..33A.178L. doi:10.1364/JOSAA.33.00A178. PMID   26974922.