Color blindness tests

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 Isihara (pseudoisochromatic) plates are used to test color vision. They are made of dot patterns composed of certain related colors. These dot patterns represent a symbol that is embedded in a background made up of different related colors. The test can determine certain abnormalities in a person's color vision.