Functional and Morphologic Consequences of Light Exposure in Primate Eyes

Abstract

To evaluate the morphologic and functional changes of the primate retina after light exposure using spectral-domain optical coherence tomography (SD-OCT) and electroretinography (ERG). Seven monkey eyes with light-emitting diode (LED) contact lenses were exposed to light for 8 hours. SD-OCT and ERG were performed bilaterally before, after the light exposure, and on days 1 and 14 in three monkeys. The tests were repeated after 4 months, followed by enucleation 12 hours later. Six eyes of three other animals were enucleated 12 hours after the first light exposure, and two eyes of one monkey were enucleated after 14 days, followed by microscopy. Immediately after light exposure, SD-OCT showed increased reflectivity of the outer segment (OS). Electron microscopy showed intracellular vacuolated and irregular lamellar structures at the proximal OS, while the distal end of the OS was unfolded at the RPE interface. At 14 days, the histologic changes and the OCT images returned to normal. ERG showed decreased cone and rod responses immediately after light exposure and decreased cone responses on day 1. Normalization occurred on day 14. Light exposure caused increased reflectivity of the photoreceptor OS, which corresponded to intracellular vacuolization and irregularity of the lamellar structure of the OS. OCT images returned to normal along with the histologic restoration. Rod and cone responses decreased transiently immediately after light exposure, which might be attributed to incomplete recovery from retinal bleaching.