Retinal damage by light in rats.

Abstract

The retina of laboratory rats is affected irreversibly by intense light applied for less than 1 hour or for up to 2 days depending upon experimental conditions. Exposure of unanesthetized and unrestrained animals was in chambers surrounded by a green filter and circular fluorescent lamps of a nominal brightness of 2,040 footlamberts. Eyes of anesthetized animals were exposed diffusely to either the light from a 100 to. zirconium arc passing through filters or monochromatic light of various icavelengths. Irreversible reduction in ERG amplitudes and degeneration of visual cells and pigment epithelium indicated the severity of the light damage. The effect was very dependent upon the body (eye) temperature during exposure. Hyperthermia greatly accelerated and intensified the damaging action of light and for this reason most experiments reported in this paper were performed at a high body temperature. At a body temperature around 104° F. severe damage teas produced with exposures to 5 to 10 iiw per square centimeter retina for 1 hour. The minimal damaging dose at a high temperature was estimated to be about 1 ixw per square centimeter. The action spectrum~of the daviaging effect approximated that of visual excitation as measured by the ERG. Hooded (pigmented) animals were no more affected than albinos of different strains. Recovery in the dark from a just subliminally damaging dose of light at a high body temperature required about 24 hours and was preceded by a period of time during ichich the retina was sensitized to an additional dose. During or following exposure to light at a high body temperature visual cell and pigmentepithelial_damage developedTabout simultaneouslu and was first indicated bit pyknosis Trncl cell swelling followed rapidly by the dissolution of nuclei and cytoplasm. The crucial reaction in producing the damage is considered a dark-reaction initiated by light of an -inte7isiiTj_ which bleaches measurably rhodopsin. Hypotheses on the reaction sequence which 'leads to damage are briefly discussed.