Involvement of Neurons in Retinal Light-Induced Changes in Pigmented Rabbits

Abstract

Purpose:: Light is involved in the physiopathology of several retinal diseases including age-dependent macular degeneration and retinitis pigmentosa. However, it still remains unclear which part of the visual spectrum is responsible for retinal damage. This is of capital importance in order to prevent the retinal lesions induced by light. Furthermore, most of the data available on the cytotoxic effects of light are focused in photoreceptors whereas the effects of light in other cell types of the retina, especially neurons, are less known. The present study was designed to investigate the effects of circadian exposure to light on the retina, and the protective effects of intraocular lens designed to filter the blue or yellow parts of the visual spectrum.

Methods:: Adult pigmented rabbits were exposed to circadian white light during different periods, after which transparent and yellow intraocular lens were implanted. The eyes of the control and experimental animals were processed for apoptosis detection (TUNEL technique), to label bipolar and ganglionic neurons, as well as plexiform layers (immunohistochemistry for neuron specific enolase, PGP 9.5, and phosphorylated 200 kDa neurofilaments).

Results:: The exposure to continuous light showed a decrease in the number of immunolabelled bipolar, but not ganglionic, neurons and an increase in the density of TUNEL-positive nuclei in the nuclear inner layer. The density of both outer and inner plexiform layers was also reduced. Intraocular lens filtering the blue portion of the visual spectrum were able to counteract these effects without reaching the levels of control animals.

Conclusions:: Present results demonstrate that in addition to photoreceptors, neurons are also involved in ligh-induced retinal damage.

Keywords: age-related macular degeneration • intraocular lens • apoptosis/cell death