Ans. b. Neovascularization at disc (Ref: Kanski 5/e p447-449; Khurana 4/260-262, 3rd/256-258; Parson's 21/307, 20/e p294-299)In diabetic retinopathy, neovascularization caused by vasculoformative substance elaborated by hypoxic retinal tissue in an attempt to revascularize retina, seen especially at disc (neovascularization of disc), bleeds due to leaky blood vessels and leads to vitreous haemorrhage." Bleeding from newly formed vessels (neovascularization) is the most common cause of spontaneous vitreous hemorrhage in diabetic adults. Proliferative new leaking vessels usually arise from retinal veins. Sudden vitreous contractions tear the fragile new vessels, causing vitreous hemorrhage. Most diabetic vitreous hemorrhage occur during sleep, probably because of an increase in blood pressure secondary to early morning hypoglycemia or to REM sleep."Diabetic RetinopathyMicroangiopathy, which affects the retinal pre-capillary arterioles, capillaries and venules.It causes microvaseular and macrovascular occlusionQ.Microvascular OcclusionMacrovascular OcclusionA-V shunt formationQNeovascularizationQRetinal hemorrhageQRetinal edemaQ* Associated with significant capillary occlusion, referred as intraretinal microvascular abnormalities (IRMA)QCaused by vasculoformative substance elaborated by hypoxic retinal tissue in an attempt to revascularize retina. It may be:* NVD: New vessels at the discQ (optic nerve head)* NVE: New vessels elsewhere (along the course of major blood vessels)Q* Rubeosis iridis: new vessels on the irisQ* Dot and blot shapedQ arise from venous end* Flame shapedQ arise from precapillary arterioles* Hard exudatesQ, yellow waxy lesions with distinct margins often arranged in rings (circinate exudates)* Soft exudates (cotton wool spots)Q