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': 'Astigmatism is due to – \nSelect and explain. \nA. Irregularity of curvature of cornea, B. Irregularity of curvature of lens, C. Forward displacement of the lens, D. Backward displacement of lens', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Most common cause of astigmatism is abnormalities of curvature of cornea.', 'role': 'assistant'}]