<prompt> ETDRS vision chart study is done in patients with diabetic retinopathy. ETDRS stands forExtended therapy for diabetic retinopathy its sutdyEmergency treatment for diabetic retinopathy and studyEye testing or rotatory drum its studyEarly treatment for diabetic retinopathy study  <response>: Early treatment diabetic retinopathy study ETDRS was a multicenter, randomized clinical trial involving 3711 participants designed to evaluate the effectiveness of both organ laser photocoagulation and aspirin therapy in the management of patients with non-proliferative diabetic retinopathy and early proliferative diabetic retinopathy.In addition, it was designed to determine the best time to initiate photocoagulation treatment in diabetic retinopathy. 