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Color blindness and color weakness tests using color - coded pictures are important methods to detect an individual's color vision deficiencies. These tests usually consist of a series of pictures, known as Ishihara plates.
Principle
The Ishihara plates contain numbers, patterns, or symbols made up of colored dots. The dots are carefully selected so that people with normal color vision can clearly distinguish the figures, while those with color blindness or color weakness may see different figures or be unable to identify them at all. For example, in a plate designed to test red - green color blindness, the numbers are composed of red - colored dots on a green - colored dot background. A person with normal color vision can easily see the number, but a red - green color - blind person may not be able to differentiate between the two colors and thus miss the number.
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