Keratitis is inflammation of the cornea, caused by bacterial, viral and fungal infections. Classically the cornea becomes swollen and infiltrates occur, accompanied by a red eye with varying degrees of discomfort and pain. In the worst case corneal ulceration can occur and it is thus important to treat promptly. The main cause of keratitis in contact lens wearers is microbial infection by bacteria or amoeba Acanthamoeba. This is a difficult pathogen to eliminate from the cornea and the keratitis it produces has a poor prognosis unless diagnosed early.