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': 'Not a symptom of angle closure glaucoma – \nSelect and explain. \nA. Blurring of vision, B. Coloured Halos, C. Metamorphosia, D. Headache', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Transient blurring of vision and headache is seen in stage of constant instability.\nColoured halos are seen in acute congestive stage.', 'role': 'assistant'}]