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
Keratoconus is defined as: March 2013 (h) 
Select and explain. 
A. 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
C: Cornea thins near the centre & bulges forwards
Answer: C: Cornea thins near the centre & bulges forwards 
Explanation: Ans. C i.e. Cornea thins near the centre & bulges forwards