Irreversible effects on visible light on the retina: role of vitamin A.

Diffuse retinal irradiation by visible light produces in the rat the death of visual cells and pigment epithelium. Typically, cage illumination of 1500 lux from fluorescent light through a green filter leads to severe damage when continued for 40 hours. Vitamin A deficiency protects against this damage but experiments show that retinol released by light from rhodopsin is probably not the toxic agent. Protection against light damage depends on a long-range state of cell adaptation to light itself. The normal diurnal cycle of light and dark seems to be the essential factor in controlling visual cell viability and susceptibility.