dark adaptation

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dark adaptation

The process by which the iris and the retina of the eye adjust to allow maximum vision in dim illumination following exposure of the eye to a relatively brighter illumination. In darkness, vision becomes more sensitive to light, provided a person has not been exposed to bright light for some time. Although exposure to total darkness for at least 30 minutes is required for complete dark adaptation, a pilot can achieve a moderate degree within 20 minutes under dim red cockpit lighting. Dark adaptation is impaired by exposure to cabin pressure altitudes above 5000 ft, carbon monoxide inhaled in smoking and from exhaust fumes, deficiency of vitamin A in the diet, and prolonged exposure to bright sunlight.