Continuous red light induces persistent estrus without retinal degeneration in the albino rat.

Female rats were exposed for 12 weeks to red (peak 660 nm) or Cool White continuous light (LL), or to 12 h per day (LD) of Cool White light, all at a flux density of 100 muw/cm2 (approximately 30 incident foot-candles). Either red or white LL produced significantly prolonged vaginal cornification and significantly reduced ovarian weight, as compared to LD exposure. White LL, but not red LL, produced degeneration of retinal photoreceptors.