Keratitis is inflammation of the cornea of the eye. The cornea is the curved transparent layer in front of the eye. Keratitis can be provoked by diferent causes, one of which is viral keratitis, which is an infection of a herpes simplex virus secondary to an upper respiratory infection, involving cold sores. Bacterial keratitis can follow from an injury or from wearing contact lenses; the bacteria usually involved are Staphylococcus aureus and for contact lens wearers Pseudomonas aeruginosa. Fungal keratitis is caused by a fungi infection, especially fusarium. Amoebic keratitis is the most serious corneal infection, usually affecting contact lens wearers, and is caused by Acanthamoeba.
Keratitis can also be classified by its location. Superficial keratitis affects the superficial layers of the cornea; this form of keratitis does not generally leave a scar after healing. Deep keratitis involves deeper layers of the cornea, and the natural course leaves a scar upon healing that impairs vision if on or near the visual axis. This can be reduced or avoided with the use of topical corticosteroid eyedrops. Treatment depends on the cause of the keratitis. Infectious keratitis generally requires antibacterial, antifungal, or antiviral therapy to treat the infection. This treatment can involve prescription eye drops, pills, or even intravenous therapy.