Color Deficiency - vision impairment

Color Deficiency - vision impairment

Color Deficiency a VISION IMPAIRMENT in which the ability to distinguish certain, and rarely all, colors is impaired. Color deficiency represents a shortage of normal cones, the specialized cells on the RETINA that detect color. Cones contain photosensitive chemicals that react to red, green, or blue. The most common presentation of color deficiency, accounting for about 98 percent of color deficiency, is red/green deficiency, in which the person cannot distinguish red and green. A small percentage of people cannot distinguish blue and yellow. Rarely, a person sees only in shades of gray.

Color perceptions occur when lightwaves of certain frequencies (lengths) activate the photochemicals in cones that are sensitive to the frequency. The BRAIN interprets the varying intensities and blends of the photochemical responses. Color deficiency occurs when the cones that perceive one of the three primary colors (red, green, blue) do not function properly.

Color Deficiency - test

The most common test for color vision and color deficiency is a series of disks that contain dots of color in random patterns with a structured pattern of differing color within the field. The structured pattern may be a number (most commonly) or an object. There is no treatment to compensate for color deficiency. People who are color-deficient learn to accommodate the deficiency through mechanisms such as memorizing the locations of colored objects (such as the sequence of lights in a traffic signal) and by making adaptations in their personal environments. A person may have friends or family members sort clothing by color, for example, and label the color groups. Some people who have mild color deficiency experience benefit from devices such as colored glasses and colored contact lenses that filter the lightwaves that enter the EYE. A yellow tint may improve blue-deficient color vision, for example.

Causes of Color Deficiency

Most color deficiency is an X-linked genetic MUTATION, affecting about 8 percent of men and 1⁄2 percent of women. Color deficiency may also develop with AGE-RELATED MACULAR DEGENERATION (ARMD), RETINOPATHY, neurologic disorders such as MULTIPLE SCLEROSIS, and HEAVY-METAL POISONING such as lead or mercury. Antimalarial drugs can cause permanent changes in the RETINA that affect color vision; the ERECTILE DYSFUNCTION medication sildenafil (Viagra) can temporarily intensify the perception of blue.

See also VISION HEALTH; VISUAL ACUITY.

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