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Overview

Color vision deficiency results from a malfunction or absence of cone cells in the retina. The degree of deficiency ranges from a slight difficulty distinguishing among different shades of one color to the inability to see any color. There are millions of photoreceptor cells in the human eye's retina that contain photosensitive pigments. There are two types of these specialized cells: cones and rods. Each retina contains approximately 6 million cones and over 100 million rods.

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