This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
[{'content': 'Visual loss in diabetic retinopathy is due to all except: \nSelect and explain. \nA. Cataract formation, B. Background diabetic retinopathy, C. Ischaemic maculopathy, D. Vitreous hemorrhage', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Background diabetic retinopathy', 'role': 'assistant'}]