Photocoagulation of Iris and Retina

The eye offers unique opportunities for study of the effects of focused radiant energy because of the transparency of the media. Because radiation affects only those tissues in which it is absorbed (Draper's law), visible and infrared rays pass through the transparent media of the eye and may damage only those tissues which absorb this energy—the pigment layer of the iris and retina. When a high-powered beam from the sun or a carbon arc lamp is focused on one part of the iris, the rays can produce considerable damage to the iris. By the same token, if radiation of sufficient intensity is focused by the dioptric media of the eye, it passes through the transparent media and burns the pigmented layer of the retina, where it is absorbed. Solar chorioretinal burns caused by looking at the sun have been known for years.¹Many investigators²⁻⁹have coagulated the iris