The effect of exposure to sunlight on night vision.

1. Exposures to ordinary sunlight produced temporary and cumulative effects on night vision. 2. After repeated daily exposures to sunlight, the delay in reaching the normal threshold persisted overnight, and the threshold after complete dark adaptation rose higher each day for about 10 days and remained at a higher level. 3. This elevated threshold corresponds to an average deterioration of about 50 percent in visual acuity, range of visibility, contrast discrimination, and in the frequency of picking up a target when it is barely visible.