998 LIGHT TOXICITY TO NEWBORN RETINA

Abstract

A prior report of the toxic effect of phototherapy on new-born nonhuman primate retina indicated that considerable acute cellular damage occurred to nonprotected eyes when exposed to 400 ft. candles of cool-white light for more than 72 hours. This preliminary report describes the long term recovery of newborn nonhuman primate retina after acute phototherapy exposure. Newborn stump-tailed monkeys (Macaca arctoides) averaging 450 gms. were placed in an incubator exposed to 400 ft. candles of cool-white fluorescent light. Periods of exposure included 24 hrs., 3, 7, and 10 days. Each right eye was occluded with black velour patch material while the left eye was left uncovered. Following the phototherapy exposure, the monkeys were returned to standard cage environments for 10 months before the retinas were processed for electron microscopy. Histologic study revealed that occluded eyes retained normal cytoarchitecture and all exposed retinas demonstrated substantial recovery although rod and cone receptor segments remained abnormal in retinas exposed for 3 or more days even after 10 months recovery. Counts of the rod and cone nuclei in the outer nuclear layer indicated a loss of viable photoreceptor cells in the unprotected eyes compared to patch occluded eyes. This loss duplicates the aging process in mammalian retina and may not be initially detectable except by histologic examination. Thus the effect of acute phototoxicity may be premature aging of the retina (loss of some rod and cone receptors) with clinically detectable results delayed until later in life.