A comparative study of photic injury in four inbred strains of albino rats

The effects of light damage were studied in four inbred strains of albino rats, Fischer (F344), Lewis (L), Wistar (W), and Buffalo (BUF). Thirty-five-day-old rats (3 from each strain) were kept in cyclic light for two weeks, after which they were exposed to constant fluorescent light (180-190 foot-candles, 490-580 nm) for 24 hours. The rats were sacrificed 6 days after exposure. Photic injury to the exposed eyes was evaluated morphometrically by measuring the mean outer nuclear layer (ONL) thickness and qualitatively by light microscopy. Statistical analysis of the quantitative data revealed that the Lewis and Buffalo strains were more severely affected than the Wistar and Fischer strains. The effects of injury were more severe in the superior and temporal quadrants. Taking both quantitative and qualitative assessment into consideration, it appeared that, among the strains studied, the rats from the Lewis strain were most sensitive to photic damage. These findings support previous findings of differential light sensitivity and further suggest that similar variability occurs among inbred strains with type 1 light damage.