Cornea

The cornea is the transparent tissue, the "windshield" that covers the eye. It shields the inside of the eye from germs, dust and other harmful matter. The cornea allows light into the eye and acts as a very powerful lens to focus light rays on the back of the eye.

Corneal problems can range from minor injuries or abrasions to more severe diseases. Usually the minor abrasions heal on their own as the cells quickly regenerate to cover the injury before the infection occurs and vision is affected. However, infections can occur and usually are treated with anti-bacterial or anti-fungal eye drops. Conjunctivitis, ocular herpes and herpes zoster are other more severe conditions that may affect the cornea. Other problems, such as keratoconus -- a steep curving of the cornea, and Fuch's dystrophy -- deterioration of epithelial cells causing the cornea to swell and distort vision, can cause the need for a corneal transplant.

A corneal transplant is an operation in which the diseased or damaged cornea is removed and replaced with a healthy donor cornea. The need for a corneal transplant arises if the cornea becomes swollen or scarred, thus altering the clarity and smoothness of the cornea. This causes the cornea to distort light, resulting in glare or blurred vision. Once the donor cornea is carefully sewn into place, it provides a clear pathway for light to reach the retina. Corneal transplants are needed because of corneal failure after other eye surgeries such as cataract surgery, keratoconus, heredity, scarring after infections, especially after herpes, or rejection after the first corneal transplant.

Corneal transplants are more common and more successful than all other transplant surgeries including heart, lung and kidneys. Ophthalmologists perform more than 40,000 corneal transplants each year and are about 90% successful.