Eye Exams

Colour blindness test: Do you see colours correctly?

ishihara color blind test
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A colour blind test is a device your eye doctor uses to determine if you have a colour vision deficiency, commonly known as colour blindness.

If you think you might be colour blind, find an eye doctor near you and get an eye exam. consult an eye doctor. (Click here to find an eye doctor near you.)

There are two types of colour blind tests:

  1. Brief screening tests that can detect the presence of a colour vision deficiency
  2. More detailed tests that can detect and determine the type and severity of colour blindness.

Screening colour blind tests

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

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 colorued 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. But 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.

The complete Ishihara Colour Vision Test contains 38 plates. Abbreviated versions that contain 14 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.

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 color ("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.

Since the introduction of the Ishihara Colour Vision Test, medical device companies have developed similar colour blindness screening tests using pseudoisochromatic plates.

For example, the ColorDx computerized colour vision test (Konan Medical) is a self-administered, self-scoring app that comes preloaded on an Android tablet.

In addition to testing for genetic color blindness, the ColorDx app can detect colour vision deficiencies that can develop later in life due to glaucoma, multiple sclerosis, diabetic retinopathy, macular edema and other disorders, as well as colour vision problems associated with long-term use of medications and other substances, according to the company.

Quantitative colour blind tests

For a more detailed analysis of colour blindness and/or a person's ability to accurately perceive colours, a quantitative colour blind test is needed.

The most popular quantitative colour blind test is the Farnsworth-Munsell 100 Hue Test.

This test consists of four trays containing many small disks of varying hues. Each tray has a coloured reference disk at one end. The person being tested must arrange the other disks within the tray to create a continuum of gradually changing hue.

For accurate results, the Farnsworth-Munsell 100 Hue Test should be administered in a viewing booth that simulates natural daylight as closely as possible. Also, the coloured disks should be replaced at least every two years to prevent loss of colour saturation that could affect outcomes.

Each colored disk is numbered on the bottom to enable scoring the results against a key. The closer the match between the test sequence of caps and the correct sequence, the more accurate the person's colour perception is.

In this fashion, the 100 Hue Test can detect whether or not the person being tested is colourblind and also determine the type and severity of his or her colour blindness.

An abbreviated version of the 100 Hue test — called the Farnsworth-Munsell D15 Test — contains only 15 numbered disks of different hues. The D15 test, like the Ishihara Colour Vision Test, is for colour vision screening purposes only, and cannot quantify the severity of a person's colour blindness.

Who should take a colour blind test?

A colour blind test should be given to anyone considering a profession in which 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 colour-related requirements of the position and the severity of the person's colour vision deficiency.

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 cure for colour blindness, in some cases specially tinted eyeglasses or contact lenses may improve a colourblind person's ability to perceive the differences between certain colours.

Online colour blind tests

Many colour blind tests can be found online. These almost always are variations of the Ishihara screening test and are presented in varying degrees of quality.

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 evaluation of your colour vision, consult an eye doctor and take a colour blind test under proper lighting using standardized testing materials.

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