A randomized clinical trial of early panretinal photocoagulation for ischemic central vein occlusion. The Central Vein Occlusion Study Group N report.

To answer whether prophylactic panretinal photocoagulation (PRP) in ischemic central vein occlusion (CVO) prevents development of 2 clock hours of iris neovascularization or any angle neovascularization (TC-INV/ANV) or whether it is more appropriate to apply PRP only when TC-INV/ANV occurs.Multicenter randomized controlled clinical trial in eyes with ischemic CVO. Eyes were assigned to immediate prophylactic PRP (90 eyes) or to frequent close observation (91 eyes). If TC-INV/ANV developed, untreated eyes received PRP and previously treated eyes received supplemental PRP.In both groups, TC-INV/ANV developed less often in prophylactically treated than untreated eyes, but the difference was not statistically significant when adjusted for baseline imbalance. Treatment of TC-INV/ANV was followed by prompt regression (within 1 month) in 18 (56%) of 32 previously untreated eyes and in 4 (22%) of 18 eyes that had had prophylactic treatment. All eyes except eight eventually stabilized without neovascularization. TC-INV/ANV was correlated with the amount of nonperfused retina (P = 0.0001) and extent of retinal hemorrhage (P = 0.03). Males were at higher risk than females for TC-INV/ANV (P = 0.01), as were patients with occlusions of less than one month duration (P = 0.01).Prophylactic PRP does not totally prevent TC-INV/ANV, and prompt regression of TC-INV/ANV in response to PRP is more likely to occur in eyes that have not been treated previously. The authors recommend careful observation with frequent follow-up examinations in the early months (including undilated slit-lamp examination of the iris and gonioscopy) and prompt PRP of eyes in which TC-INV/ANV develops.