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': 'Keratoconus is defined as: March 2013 (h) \nSelect and explain. \nA. Degeneration of conjunctiva, B. Cornea undergoes necrosis due to vitamin A deficiency, C. Cornea thins near the centre & bulges forwards, D. Recurrent corneal ulcerations of cornea', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C i.e. Cornea thins near the centre & bulges forwards', 'role': 'assistant'}]