The effect of long-term irradiation with fluorescent light on the rat fundus.

In the rat, continuous exposure to so-called "cold light" of 800 lux leads to a nearly complete loss of retinal photoreceptors, which occurs within 4 weeks. This process is followed by vascularization of the retinal pigment epithelium (RPE). The origin, extent, and expansion of such proliferations within 6 months after the onset of irradiation were evaluated by means of light microscopy, transmission electron microscopy, scanning electron microscopy, corrosion cast preparation, india ink injection, and trypsin digest preparation. The vessels within the RPE were found to be fenestrated and to form a network with the vessels of the neurosensory retina. Invasion of Bruch's membrane and formation of chorioretinal anastomoses were not observed. The occurrence of vessels within the RPE coincided with a massive regression of capillaries in the neurosensory retina.