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': 'Coloured halo is seen in all except: \nSelect and explain. \nA. Open angle glaucoma, B. Closed angle glaucoma, C. Cataract, D. Any of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Open angle glaucoma', 'role': 'assistant'}]