Dysfunction of the blood-retina barrier following white light exposure. A tracer study with horseradish peroxidase and ferrous gluconate.

The aim of this investigation was to study the ultrastructural effects of white light on the retinas of pigmented rabbits. The retinas were exposed to white light (400-740 nm) at intensities between 65 and 140 mW/cm2 for 1 h. Two days after exposure, the increased leakage of fluorescein measured with vitreous fluorophotometry could be mimicked on electron microscopy by the tracers ferrous gluconate and horseradish peroxidase (HRP). In cases of minimal fluorescein leakage, traces of HRP were found in the basal folds of the retina pigment epithelium (RPE). No HRP was observed apical to the tight junctions of the RPE cells. When there was a great amount of fluorescein leakage, HRP completely filled the RPE cytoplasm, the extracellular spaces, and several cells in the neuroretina. It is concluded that after exposure to low intensities of white light, blood-retina barrier dysfunction may be due to disruption of the RPE basal fold membrane, leading to increased transcellular passage. The intact tight junctions suggest the under these circumstances intercellular leakage is not a component of BRB dysfunction.