Swelling and Loss of Photoreceptors in Chronic Human and Experimental Glaucomas

Abstract

<h3>Objective</h3> To determine whether outer retinal changes occur in chronic, presumed primary open-angle glaucoma (POAG). <h3>Methods</h3> The outer retinas from 128 human eyes with a diagnosis of chronic glaucoma (presumably POAG in most cases) and 90 control eyes were examined histologically by 3 masked observers for photoreceptor swelling and loss. Retinas from 9 rhesus monkeys with glaucoma induced experimentally by laser trabecular destruction were compared with 7 fellow (control) eyes. The mean pressure elevations in the eyes with laser trabecular destruction ranged from 26.6 to 53.6 mm Hg with durations varying from 7 to 33 weeks. <h3>Results</h3> Swelling of the red- and green-sensitive cones was observed in a statistically significantly greater proportion of human eyes with presumed POAG compared with the control eyes. Patchy loss of red/green cones and rods was also found in some of the glaucomatous retinas. In a subset of the human eyes with end-stage disease, cone swelling was a variable finding. Although no photoreceptor loss was found in the 9 monkey eyes with experimental glaucoma, 8 had swelling of their red/green cones that was remarkably similar to that seen in the human eyes. Swelling was not present in any of the control monkey eyes. <h3>Conclusions</h3> The photoreceptors are affected by chronically elevated intraocular pressure. <h3>Clinical Relevance</h3> These findings may explain some of the abnormalities of color vision and the electrophysiological effects that have been observed in patients with POAG.