<prompt> Most common cause of infectious keratitis in a contact lens userAcanthamoebaPneumococcusPseudomonasStaph  <response>: Most common cause of infectious keratitis in a contact lens user is pseudomonas Commonest causative organism associated with keratitis - pneumococcus Hypopyon ulcer ulcus serpens - pneumococcus acanthamoeba : attacks contact lens that are washed with water. 