Moderate and severe non‐proliferative diabetic retinopathy

Microaneurysms in increasing numbers have been shown to be an important early measure of progression of diabetic retinopathy. The main features that warrant classifying a diabetic retinopathy level in the higher levels of moderate and severe non‐proliferative diabetic retinopathy (NPDR) are increasing signs of retinal ischaemia. Lesions associated with increasing retinal ischaemia include: retinal haemorrhages; intraretinal microvascular abnormality (IRMA); and venous beading. Increasing numbers of haemorrhages, particularly when the pattern of haemorrhages includes an increasing number of blot haemorrhages, denotes increasing retinal ischaemia and progression of DR. Blot haemorrhages are usually in a deeper retinal layer than more superficial dot haemorrhages and flame haemorrhages. In the UK Screening Classification, pre‐proliferative DR is defined by any of: venous beading; venous reduplication; IRMA; or multiple deep, round or blot haemorrhages. Intraretinal microvascular abnormalities are derived from remodelling of the retinal capillaries and small collateral vessels in areas of microvascular occlusion