Temporal sequence of changes to the gray squirrel retina after near-UV exposure

Monocularly aphakic gray squirrels (Sciurus carolinensis) were exposed for 10 min to monochromatic near-ultraviolet radiation (lambda = 366 nm, radiant exposure = 4.3 J/cm2) to determine if their yellow pigmented lens protected retinal tissue from photochemical damage. Eyes were examined from 1 to 30 days after exposure to determine the temporal sequence of retinal damage and the extent of recovery from such exposures. Light microscopy of exposed aphakic retinas revealed irreversible lesions to the photoreceptors. Swelling of inner segments, accumulation of heavy pigment deposits in the PE, presence of macrophages in the subretinal space, and pyknosis of photoreceptor nuclei were observed in the exposed region of the aphakic eye. Eyes exposed to ultraviolet radiation with their lenses intact were devoid of significant retinal lesions. This study represents a model system for studying the potential damaging effects of near-UV radiation to the aphakic eyes of humans.