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Snow blindness.—The temporary diminution or loss of sight of varying degree, occurring when unprotected eyes are subjected to the intense light reflected from the snow, is known as snow blindness. It may occur on cloudy days as well as clear, and is particularly apt to occur on brilliant days in the spring, when the sun is high and the days are long. More harmful rays exist at high altitudes because there is less in the air to absorb them. The action of reflected light from the snow is threefold. Ultraviolet light causes "sunburn" of the conjunctiva and cornea. The dazzling visual rays cause squinting and, finally, spasm of the muscles surrounding the eye. The infrared rays may coagulate the protein of the structure of the eye. The effect of light on the eye is cumulative to the extent that many short, repeated exposures in one day are about as damaging as one longer continuous exposure. |
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