Photoreceptor degeneration after exposure of rats to incandescent illumination

Summary

The retina of the albino rat undergoes degenerative changes when exposed to low intensity incandescent light. The retinal degeneration is limited specifically to the photoreceptor cells, and the pigment epithelium is unaffected. Early changes in the receptors included fragmentation of the inner and outer segments and pyknosis of the receptor cell nuclei. Phagocytic cells invaded and occupied the central retinal area of degeneration, between the receptor layer and the pigment epithelium, in the 4 and 5 day exposure periods. They were absent centrally after 14 and 30 days of exposure, but were present at these time periods in the peripheral retina, where photoreceptor destruction was still in progress. The destruction of photoreceptor cells, including the receptor and outer nuclear layers of the retina, by incandescent light progressed at a slightly reduced rate as compared to that after exposure to fluorescent light of the same intensity. These experiments indicate that exposure to either low intensity incandescent or fluorescent light will cause a selective degeneration of retinal photoreceptor cells, and therefore provide an easily reproducible model for the study of retinal structure and function in the absence of the receptors.