Photochemical injury to the foveomacula of the monkey eye following argon blue-green panretinal photocoagulation

Purpose: Visual loss following panretinal photocoagulation was found in the Diabetic Retinopathy and the Early Treatment Diabetic Retinopathy Studies. This study was designed to test the hypothesis that light scattered in the monkey eye during a procedure designed to mimic a clinical panretinal photocoagulation (PRP) can produce a photochemical injury to the foveomacula. Methods: Ten eyes of 5 adult cynomologous monkeys underwent a PRP using an Argon blue-green laser. Three eyes in 2 monkeys underwent a sham PRP, and an additional eye had a PRP with blue filtered slit-lamp illumination. The animals had baseline fundus photographs and fluorescein angiograms that were repeated 24 hours after the experimental procedure. Forty-eight hours after the experimental procedure, the eyes were removed and processed for light and electron microscopy. Results: There were no observable changes in the macula on fundus photography or fluorescein angiography 24 hours following PRP. Light and electron microscopy demonstrated changes in the retinal pigment epithelium and the outer photoreceptors, which were confined to the foveola. The control eyes showed no apparent effect from the slit lamp illumination used during the PRP. Conclusions: The presence of histologic evidence of retinal injury in the foveomacula of the monkey eye after a procedure designed to mimic clinical PRP supports the hypothesis that photochemical retinal damage in the foveola may be associated with this procedure.