The modified Airlie House classification has been used to classify nonproliferative diabetic retinopathy (NPDR) since the Diabetic Retinopathy Study (DRS) and Early Treatment Diabetic Retinopathy Study (ETDRS). (1-3)  Since this classification determines management of nonproliferative diabetic retinopathy, it is extremely important to know these criteria.  This classification has been further refined by Wilkinson et al for international use and was adopted as part of the AAO's Preferred Practice Pattern for Diabetic Retinopathy. (4,5)