Inflammation of the cornea (the transparent membrane at the front of the eyeball), usually superficial, and caused by bacteria, viruses or sometimes fungus. Damage to the cornea by exposure to radiation is also called keratitis. Symptoms are irritation of the eye, pain, redness, weeping and hypersensitivity to light. Bacterial infection can occur after damage to the cornea – by a splinter of metal, for example. The bacteria cause an ulcer, usually restricted to the cornea, although sometimes the ulcer penetrates it and infection spreads to the front chamber of the eye. Inflamed cells cause clouding of the iris, and the cells themselves form a deposit visible as a half moon on the underside of the iris. Treatment is by cleaning the affected part of the cornea, and with antibiotics. Keratitis can also be caused by various viruses. In the first stage a number of small blisters can be seen on the cornea; they then run together, and finally form a branched area of damage, which shows up clearly with a special dye. Treatment is by eye drops or eye ointment and antiviral medication. It is important not to use drops or ointments containing corticosteroids because they could aggravate the condition. Keratitis is often a consequence of a disorder that affects the whole body such as syphilis or rheumatic disorders. Exposure of the cornea to ultraviolet radiation or X-rays can also cause the condition. Damage in the form of small spots can be seen on the cornea. Usually only painkillers are necessary, and the keratitis clears up within 24 hours.