Causes of severe visual loss in the early treatment diabetic retinopathy study: ETDRS report no. 24

PURPOSE: To describe the causes of and risk factors for persistent severe v isual loss occurring in the Early Treatment Diabetic Retinopathy Study (ETD RS). METHODS: The ETDRS was a randomized clinical trial investigating photocoagu lation and aspirin in 3,711 persons with mild to severe nonproliferative or early proliferative diabetic retinopathy. Severe visual loss, defined as b est-corrected visual acuity of less than 5/200 on at least two consecutive 4-month follow-up visits, developed in 257 eyes (219 persons). Of these 257 eyes, 149 (127 persons) did not recover to 5/200 or better at any visit (p ersistent severe visual loss). Ocular characteristics of these eyes were co mpared with those of eyes with severe visual loss that improved to 5/200 or better at any subsequent visit. Characteristics of patients with severe vi sual loss that did and did not improve and those without severe visual loss were also compared. RESULTS: Severe visual loss that persisted developed in 149 eyes of 127 per sons. In order of decreasing frequency, reasons recorded for persistent vis ual loss included vitreous or preretinal hemorrhage, macular edema or macul ar pig mentary changes related to macular edema, macular or retinal detachm ent, and neovascular glaucoma. Compared with all patients without persisten t severe visual loss, patients with persistent severe visual loss had highe r mean levels of hemoglobin A(1c) (10.4 % vs 9.7%; P = .001) and higher lev els of cholesterol (244.1 vs 228.5 mg/dl; P = .0081) at baseline. Otherwise , patients with persistent severe visual loss were similar to patients with severe visual loss that improved and to those without severe visual loss. CONCLUSIONS: Persistent severe visual loss was an infrequent occurrence in the ETDRS. Its leading cause was vitreous or preretinal hemorrhage, followe d by macular edema or macular pigmentary changes related to macular edema a nd retinal detachment. The low frequency of persistent severe visual loss i n the ETDRS is most likely related to the nearly universal intervention wit h scatter photocoagulation (either before or soon after high risk prolifera tive diabetic retinopathy developed) and the intervention with vitreous sur gery when clinically indicated, (Am J Ophthalmol 1999;127: 137-141. (C) 199 9 by Elsevier Science Inc. All rights reserved.)