Light damage in the developing rat retina.

The effect of bright light on the retinas of developing albino rats was studied electron microscopically. The newly formed outer-segment lamellar membranes of newborn rats raised in continuous bright light appear to be less sensitive to the damaging effects of light, compared to those of rats raised under normal light conditions for at least two weeks. It seems to take about two days before the membranes show damage from continuous exposure to fluorescent lamps. The same brightness damages the adult outer segments within a few hours. Despite the severe damage to the outer segments, the rest of the retina develops normally for one month, and then the photoreceptor cells undergo degeneration. The retinas that have been exposed to bright light for two weeks after birth show considerable damage, but these retinas regenerate in six months.