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
Commonest cause of keratitis in soft contact lens users is: 
Select and explain. 
A. Acanthamoeba, B. Staph aureus, C. Naegleria, D. Herpes
A: Acanthamoeba
Answer: A: Acanthamoeba 
Explanation: A i.e. Acanthamoeba Pseudomonas aeruginosa is the most common organism encountered in contact lens related acute keratitis & corneal ulcer. Acanthamoeba is the 2nd most common cause.