Definition of Corneal ulcers and infections:

The cornea is the clear (transparent) tissue at the front of the eye. A corneal ulcer is an erosion or open sore in the outer layer of the cornea. It is often caused by infection.

See also: Corneal injury

Causes, incidence, and risk factors:

Corneal ulcers are most commonly caused by an infection with bacteria, viruses, fungi, or a parasite.

• Acanthamoeba keratitis occurs in contact lens users, especially in people who make their own homemade cleaning solutions.
• Fungal keratitis can occur after a corneal injury involving plant material, or in people with a suppressed immune system.
• Herpes simplex keratitis is a serious viral infection. It may cause repeated attacks that are triggered by stress, esposure to sunlight, or any condition that impairs the immune system.

Corneal ulcers or infections may also be caused by:

• Eyelids that do not close all the way, such as with Bell's palsy
• Foreign bodies in the eye
• Scratches (abrasions) on the eye surface
• Severely dry eyes
• Severe allergic eye disease
• Various inflammatory disorders

Contact lens wear, especially soft contact lenses worn overnight, may cause a corneal ulcer.