Phototoxicity to the newborn primate retina.

Newborn stump-tail monkeys were continuously exposed to 400 f-c of cool, white, fluorescent light for periods varying from 12 hr to 7 days. The right eye of each monkey was occluded by a patch of black velour material to serve as a control. The protected eyes retained normal ultrastructure; the exposed eyes showed progressive damage to the retina from the 12 hr to the 7-day exposure periods. Early changes were evident in the outer nuclear layer with darkly staining pyknotic nuclei and electrondense cytoplasmic processes that could be traced to their synaptic terminals. Late changes included marked distortion, vacuolization, and fragmentation of the rod and cone outer segments. The potential for phototoxicity to be additive to the normal aging of the retina is proposed, and we conclude that there is a sound basis for the current practice of patching the eyes of infants undergoing phototherapy.