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Color vision test

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  • Comment: A lot of these topics are already covered by color blindness article. AngusW🐶🐶F (bark • sniff) 17:56, 9 September 2022 (UTC)
  • Comment: Sorry, I am not sure where I should be replying to the decline reason. I in fact did write a new thread in the talk page for discussion. Unfortunately, this was 2 days before the talk page was apparently archived (this is a mystery to me) including the brand new threads I had just made. In 3 months there has been no action on this split discussion or any other discussion I have started for splits and mergers, including one that was made at the same time and NOT added to the archive. Despite being a fairly prevalent article, there is simply not a lot of interest on it from the editors side, especially considering the disorganized state of it last year before I started trying to improve it (and yes, I realize how this claim me sound). I was not surprised then that there has been no discussion on any of these threads, since there doesn't seem to be any current interest on improving the article in any regard. I thought 3 months was enough patience for input before executing the split in that case, and I didn't find any guidelines for how long one should wait. I've gone ahead and closed that discussion. I trust that what I have done is sufficient.

Color vision standards are tools against which human color vision can be measured. These standards 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 CVD (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.

Pseudoisochromatic Plates

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 shortened PIP - is a style of standard exemplified by the Ishihara test, generally used for screening of color vision defects.[1]

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.[1]

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.[2]

Ishihara Plates

Main article: Ishihara color test

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.[3] However, this can be attributed more to its ease of application, and less to do with its precision.[1]

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.[4]

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.[1]

Arrangement Tests

An 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.[5]

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 name.[6] 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.[6] 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.[6] 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).[7] About 50% of people who fail the Ishihara are able to pass the D15.[8]

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[9]. This test allows about 30% of individuals who fail the ishihara plates (generally those with mild CVD) to pass.[10]

Anomaloscopes

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.[11] An anomaloscope designed to detect red-green colorblindness 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.[12]

References

  1. ^ a b c d 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.
  2. ^ French A, Rose K, Cornell E, Thompson K (2008). "The evolution of colour vision testing" (PDF). Australian orthoptic journal. 40 (2): 7-15.
  3. ^ Gordon N (March 1998). "Colour blindness". Public Health. 112 (2): 81–4. doi:10.1038/sj.ph.1900446. PMID 9581449.
  4. ^ Ishihara, Shinobu (1972). Tests for Colour-Blindness (PDF). Kanehara Shuppan. Retrieved 17 June 2020.
  5. ^ 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.
  6. ^ a b c 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.
  7. ^ Eggertson, Curran. "Can cops be colorblind?". Chromaphobe. Retrieved 10 September 2022.
  8. ^ 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.
  9. ^ "Guide for Aviation Medical Examiners: Aerospace Medical Dispositions Item 52. Color Vision". Federal Aviation Administration. Retrieved 10 September 2022.
  10. ^ 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.
  11. ^ Nagel, WA (1907). "Zwei Apparate für die Augenärzliche Funktionsprüfung: Adaptometer und kleines Spektralphotometer (Anomaloskop)". Zeitschrift für Augenheilkunde. 17: 201–222.
  12. ^ Fulton, James T. "DETAILED INTERPRETATION OF THE NAGEL ANOMALOSCOPE". Retrieved 10 September 2022.
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