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
All are true for Mooren's ulcer except: 
Select and explain. 
A. Peripheral ulcerative keratitis, B. Advancing edge is undermined, C. Perforation is common, D. Floor of ulcer is quickly vascularised
C: Perforation is common
Answer: C: Perforation is common 
Explanation: Ans. Perforation is common