Color blindness is the inability to distinguish the differences between certain colors. The most common type is red-green color blindness, where red and green are seen as the same color. 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. The test can determine certain abnormalities in a person's color vision.
Review Date 2/28/2019
Updated by: Franklin W. Lusby, MD, ophthalmologist, Lusby Vision Institute, La Jolla, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.