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The Ishihara colour deficiency test

The most widely used screening test for colour blindness is the Ishihara Colour Vision Test. The test is named after Japanese ophthalmologist M.D., Dr. Med. Sc. Shinobu Ishihara (1879-1963), who devised the procedure and first published a description of it in 1917.

Shinobu Ishihara-finder ishihara test

The Ishihara Colour Vision Test consists of a booklet, each page containing a circular pattern (or “plate”) comprising many dots of various colours, brightness and sizes. The seemingly random coloured dots are arranged in such a fashion that a person with normal colour vision will see a single-digit or two-digit number within the array of dots, while a colourblind person will either be unable to see a number or will see a different number than the one seen by a person with normal colour vision.

Eye doctors use Ishihara plates to screen patients for colour vision problems. Someone with a red-green colour deficiency may not see the red number in this example.

The complete Ishihara Colour Vision Test contains 38 plates. Abbreviated versions that contain 14 plates or 24 plates are more frequently used as screening tests during a comprehensive eye exam.

People being tested generally view the Ishihara plates in normal room lighting while wearing their normal prescription glasses. Because the Ishihara test requires the person being screened to recognize and identify numbers, the test may be less reliable when testing the colour vision of very young children.

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A term frequently used to describe the colour plates of the Ishihara Colour Vision Test is “pseudoisochromatic.” This alludes to some of the coloured dots in the pattern that may at first seem equal (“iso-“) in colour (“chromatic”) with surrounding dots. But this is a false (“pseudo”) sameness, and the difference that exists enables a person with normal colour vision to detect the “hidden” number within the array of dots.

 

Who should take a colour blindness test?

A colour blind test should be given to anyone considering a profession where accurate colour perception is essential. Examples include electricians, commercial artists, designers, technicians, and certain manufacturing and marketing personnel.

The effect colour blindness has on a person’s job performance depends in large part on the color-related requirements of the position and the severity of the person’s colour vision deficiency.ishihara color test 4

In many cases, fears about being handicapped by colour blindness are unwarranted. Because the condition is present at birth, most colourblind people are unaware of their colour vision deficiency and do not find that it interferes significantly with their daily lives.

Though there is no treatment for colour blindness, in some cases specially tinted contact lenses may improve a colourblind person’s ability to perceive the differences between certain colours.

Online colour blind tests

You can take the Ishihara test online through our website. But please be aware that  because exact colour representation is essential for the accuracy of any colour blind test, results from online colour vision screening tests are suspect. For the most accurate results, see your eye doctor and take a colour blind test administered by a trained professional using standardized testing materials under proper lighting. You can also buy the test yourself through this webshop.