Peripheral neovascularization of the retina in diabetic retinopathy: fluorescein angiography classification and results of panretinal laser treatment

The prospective study reported here was based on 105 diabetic eyes with "new vessels elsewhere" (NVE), treated exclusively by panretinal laser application and followed up for 2.5 to 4 years. Fundus angiography was performed before treatment. The eyes were then classified in four categories according to the extent and location of capillary nonperfusion responsible for the NVE, namely 1) generalized ischemia (Type A); 2) extensive midperipheral ischemia (Type B); 3) moderate midperipheral ischemia (Type C); and 4) peripheral ischemia (Type D). Analysis of the neovascularization distribution pattern showed that NVE alone existed only in Type D, whereas in the other three types the neovascularization was present either only in the retina or in both the retina and the optic disk. This mixed vascularization was 100% in Type A, 71% in Type B, 31% in Type C, and nonexistent in Type D. Statistical analysis revealed a significant correlation between the type of ischemia and the location of the new vessels. The therapeutic results 3-4 months, 1 year, and 2.5-4 years after intervention showed a significant trend toward an increase in the number of eyes with recurrences when moving from Type D to Type A. This means that the prognosis of NVE after panretinal laser coagulation depends mainly on the type of retinal ischemia. The poorest prognosis is that for generalized ischemia (Type A), followed in descending order by Types B, C, and D. The critical period for increased recurrence in cases which initially responded positively to treatment is primarily in the first 3-4 months following the intervention.