Abstract
The Diabetic Retinopathy Study (DRS)1-4 was a landmark clinical trial in which intervention involved photocoagulation of one eye (randomly selected), with the fellow eye serving as an untreated control. The DRS findings demonstrated that photocoagulation for proliferative diabetic retinopathy resulted in a reduction of severe visual loss over a three-year period from 26.4% in untreated eyes to 10.5% in treated eyes.2 Moreover, the DRS identified certain characteristics that placed the eye at high risk of severe visual loss; namely (1) eyes with new vessels and preretinal or vitreous hemorrhage; and (2) eyes with new vessels on or within 1 disc diameter of the optic disc equaling or exceeding one fourth to one third of the disc area in extent, even in the absence of preretinal or vitreous hemorrhage.1-4 On the basis of the identification of those high-risk eyes, the DRS protocol was changed during the course of