Ishihara test

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Color perception test
Example of an Ishihara color test plate. The number "74" should be clearly visible to viewers with normal color vision. Viewers with red–green color blindness will read it as "21",[1] and viewers with monochromacy may see nothing.
Specialty	Ophthalmology
ICD-9-CM	95.06
MeSH	D003119
[edit on Wikidata]

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.^[2]

The test consists of a number of Ishihara plates, which are a type of pseudoisochromatic plate. Each plate depicts a solid circle of colored dots appearing randomized in color and size.^[3] Within the pattern are dots which form a number or shape clearly visible to those with normal color vision, and invisible, or difficult to see, to those with a red–green color vision defect. Other plates are intentionally designed to reveal numbers only to those with a red–green color vision deficiency, and be invisible to those with normal red–green color vision. The full test consists of 38 plates, but the existence of a severe deficiency is usually apparent after only a few plates. There are also Ishihara tests consisting of 10, 14 or 24 test plates, and plates in some versions ask the viewer to trace a line rather than read a number.^[4]