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Color blindness tests
Color blindness tests

Color vision test
Definition:
A visual exam that tests for deficiencies in color discrimination.

Alternative Names:
Vision test - color

How the test is performed:
Your health care provider will ask you to sit in a comfortable position, and the test will be explained to you. You will be shown several tests plates illustrating the types of symbols you will be asked to identify.

Usually Ishihara (pseudoisochromatic) plates are used to test color vision. They are made of dot patterns composed of primary colors. These dot patterns represent a symbol that is superimposed on a background of randomly mixed colors.

You will cover one eye, and the tester will then show you the test plates, holding them 14 inches from your face, and ask you to quickly identify the symbol found in each color scheme.
How to prepare for the test:

If your child is to have this test performed, it may be helpful to explain how the test will feel, and even practice or demonstrate on a doll. The more familiar your child is with what will happen and why, the less anxiety he or she will feel.

If you or your child normally wears glasses, they should be worn during the test.

In small children, color recognition such as a recognizing a red bottle cap may be performed instead.
How the test will feel:
The test is similar to a vision test.
Why the test is performed:

By using these plates, your health care provider can detect, classify, and estimate the degree of defect in your color vision.

In some circumstances, color vision testing is used to evaluate the function of the optic nerve. The optic nerve is the main nerve connecting the eye to the brain.
Normal Values:
Normally all symbols are distinguished.
What abnormal results mean:
This test can determine the following abnormalities:
  • protanopia (difficulty distinguishing between blue/green and red/green)
  • deuteranopia (difficulty distinguishing between red/purple and green/purple)
  • tritanopia (difficulty distinguishing between yellow/green and blue/green)
  • achromatopsia (complete color blindness where you can only see shades of gray)
  • optic nerve difficulties
What the risks are:
There are no risks associated with this test.
Review Date: 11/9/2001
Reviewed By: Raymond S. Douglas, M.D., Ph.D., Department of Ophthalmology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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