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': 'Open angle glaucoma causes – \nSelect and explain. \nA. Sudden loss of vision, B. Difficulty in dark adaptation, C. Amaurosis fugax, D. Uniocular diplopia', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Some patients experience difficulty in dark adaptation.', 'role': 'assistant'}]