The cornea is the transparent area at the front of the eyeball. A corneal ulcer is an erosion or open sore in the outer layer of the cornea. It is associated with infection by a bacterium, virus, fungus, or parasite. See also corneal injury.

Corneal ulcers are most commonly caused by an infection with bacteria, viruses, fungi or amoebae. Other causes are abrasions (scratches) or foreign bodies, inadequate eyelid closure, severely dry eyes, severe allergic eye disease, and various inflammatory disorders.

Contact lens wear, especially soft contact lenses worn overnight, may cause a corneal ulcer. Herpes simplex keratitis is a serious viral infection. It may cause repeated attacks that are triggered by stress, exposure to sunlight, or any condition that impairs the immune system.

Fungal keratitis can occur after a corneal injury involving plant material, or in immunosuppressed people. Acanthamoeba keratitis occurs in contact lens users, especially those who attempt to make their own homemade cleaning solutions.

Risk factors are dry eyes, severe allergies, history of inflammatory disorders, contact lens wear, immunosuppression, trauma, and generalized infection.

• Eye pain
• Impaired vision
• Eye redness
• White patch on the cornea
• Sensitivity to light (photophobia)
• Watery eyes
• Eye burning, itching and discharge

• Visual acuity
• Refraction test
• Tear test
• Slit-lamp examination
• Pupillary reflex response
• Keratometry (measurement of the cornea)
• Scraping the ulcer for analysis or culture
• Fluorescein stain of the cornea

Treating corneal ulcers and infections depends on the cause. They should be treated as soon as possible to prevent further injury to the cornea. Patients usually start treatment with antibiotic that is effective against many bacteria. More specific antibiotic, antiviral, or antifungal eye drops are prescribed as soon as the cause of the ulcer has been identified.

Corticosteroid eye drops may be used to reduce inflammation in certain conditions. Severe ulcers may need to be treated with corneal transplantation.

Untreated, a corneal ulcer or infection can permanently damage the cornea. Untreated corneal ulcers may also perforate the eye (cause holes), resulting in spread of the infection inside, increasing the risk of permanent visual problems.

• Corneal scarring
• Severe vision loss
• Loss of the eye

Call your health care provider if you develop impaired vision, severe light sensitivity, or eye pain.

Prompt, early attention by an ophthalmologist for an eye infection may prevent the condition from worsening to the point of ulceration. Wash hands and pay rigorous attention to cleanliness while handling contact lenses, and avoid wearing contact lenses overnight.