The effect of prolonged indirect ophthalmoscopy on the human eye.

In an experiment designed to simulate an excessively prolonged clinical examination, seven human eyes were exposed to light focused through a 20-diopter, aspheric condensing lens for 30 to 45 minutes. Three eyes contained primary malignant tumors of the choroid and were enucleated 1 1/2 to 4 1/2 days after light exposure. Follow-up data on four blind eyes with clear media were evaluated 15 to 36 months after light exposure. Concentrated prolonged light exposure used in this experiment caused grossly visible progressive corneal edema, along with significant discomfort to the patient. Even with light exposures sufficient to cause these complications of the anterior segment, retinal injury was recognizable only with electron microscopy and was characterized by irregular bending and twisting of the outer segments of the photoreceptors, changes that are considered reversible in nonhuman primate studies. Intermediate to long-term follow-up of 15 to 36 months after light exposure to blind eyes failed to reveal lens changes or delayed light-induced degenerative changes in the retina recognizable by ophthalmoscopy, fundus biomicroscopy, or color and fluorescein fundus photography.