Effects of moderate-intensity light on vitamin A-deficient rat retinas.

The effects of moderate-intensity light (150 to 200 ft-cd) on retinal structure were compared between retinol-adequate and retinol-deficient rats after 1 to 6 days of light exposure during the 12 hr light phase of the cycle. Both damage to the outer segments and loss of photoreceptor cells were accelerated in retinol-adequate rats. Outer segments in retinas of retinol-adequate rats showed an abnormal staining pattern and disruption of disc structure in the distal portion about 2 days before those of retinol-deficient rats. After 4 days of exposure 24% of the photoreceptor cells had degenerated in the retinol-adequate retinas, but only 6% in the retinol-deficient retinas. By 6 days 65% and 41% of the photoreceptors had degenerated in the retinol-adequate and retinol-deficient retinas, respectively. Thus light exposure induced more rapid degeneration of photoreceptor cells in rats receiving adequate retinol than in those deficient in this vitamin.