THE PROTECTION TO NIGHT VISION AFFORDED BY SUNGLASSES.
NAVAL SCHOOL OF AVIATION MEDICINE PENSACOLA FLA
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The protection afforded by low transmission sunglasses to retinal sensitivity has been studied in three subjects. When the subjects wearing a 12 polarizing filter over one eye were exposed to sunlight for three to four hours, there was an immediate elevation of the night visual threshold in the unprotected eye over that of the protected eye. The threshold of the unprotected eye remained elevated overnight to a degree which is probably of practical significance. When the filter was changed to the opposite eye, there was an immediate reversal of sensitivity in the two eyes indicating that the effects of these exposures to sunlight were temporary. The results of monocular photopic Contrast Discrimination Tests given after 60 minutes of dark adaptation showed that a slight interference with cone function also occurred immediately after prolonged exposure to sunlight. This interference with cone function did not persist overnight. Author