A defect or crater in the outer layer of the cornea is called an ulcer. Ulcers are irregular in shape and depth. The edges of the ulcer tend to lift and peel away, creating a larger defect. Corneal ulcers are often the result of an abrasion or rubbing on the cornea due to trauma or having a foreign body such as a foxtail or plant awn embedded in the conjunctiva. Some ulcer can be seen just by looking at the cornea. Most of the time, a drop of dye called fluorescein is instilled and the eye is exmined using a black light. A corneal ulcer will glow apple green. Treatment involves removing the diseased tissue so that new corneal cells can grow over the defect. Antibiotics are given topically and orally along with pain control medications. If the corneal ulcer is very deep, the cornea may rupture.
To protect the eye from rupturing from a deep ulceration, the eyelids can be temporarily sutured (closed with one or two stitches) and medications carefully instilled behind the closure. Alternatively, the third eyelid or nictitating membrane may be drawn up over the cornea and sutured in place to act as a bandage over the ulcer. Thirdly, the entire ulcer may need to be removed surgically and the defect closed with tiny sutures. Most corneal ulcers heal quickly and uneventfully. Severe ulcers can result in an infection spreading to the deeper tissues of the eye. It is important to give medications and to recheck the ulcer frequently until healed.