Different determinants of neovascularization on the optic disc and on the retina in patients with severe nonproliferative diabetic retinopathy.

Almost all patients with type I and many with type II diabetes develop proliferative retinopathy. This entity consists of two components: new blood vessels on the optic disc (NVD), which frequently lead to visual loss, and new blood vessels elsewhere on the retina (NVE), which do not pose such a serious threat to vision. This study examined determinants of neovascularization specifically on the optic disc in eyes with severe nonproliferative retinopathy. The study eyes were under surveillance as the untreated control eyes of participants in the Diabetic Retinopathy Study. During the 5-year follow-up period, NVE developed in almost all of the eyes, whereas the cumulative incidence of NVD in these same eyes was 64% and varied according to several factors. The risk of NVD in a study eye was increased if the contralateral treated eye had NVD rather than NVE or severe nonproliferative retinopathy (odds ratio [OR], 6.1; P < .0001). It was also increased if the study eye had, at the baseline examination, soft exudates and intraretinal microvascular abnormalities (OR, 5.7; P = .002) or soft exudates alone (OR, 4.0; P = .04). Nephropathy and poor glycemic control were each associated with a two-fold increase in risk but neither was statistically significant. Eyes of individuals over 40 years of age were protected from the development of NVD (OR, 0.5; P < .05). The findings of this study support the hypothesis that, in patients with diabetes, the development of NVD is determined by different factors than the development of NVE.