This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Retina, Subject name: Ophthalmology
Most Common cause gradual vision loss in Diabetic Retinopathy: 
Select and explain. 
A. Cataract, B. Macular edema, C. Glaucoma, D. Keratoconus
B: Macular edema
Answer: B: Macular edema 
Explanation: Macular edema is the most common cause of gradual vision loss. Explanation: Since retinopathy is asked answer would be macular edema, but if diabetes in general would have been asked then answer will be Cataract. Remember most common cause of sudden vision loss in adult with proliferative diabetic retinopathy is vitreous hemorrhage.