This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2019, Subject name: Ophthalmology
ETDRS grading of vision is done for 
Select and explain. 
A. Endothelial count, B. Corneal topography, C. Primary open angle glaucoma, D. Classification of diabetic retinopathy
D: Classification of diabetic retinopathy
Answer: D: Classification of diabetic retinopathy 
Explanation: ETDRS - Early treatment diabetic retinopathy study It is the best cha to measure the vision It is used to early treatment diabetic retinopathy