The cornea is the eye’s outermost layer. It is a clear dome of tissue that allows light to enter the eye. If the cornea becomes diseased or damaged, it can distort or even block the normal path of light into the eye. When this happens, light does not focus normally on the retina, the layer at the back of the eye that is responsible for sight. As a result, there can be significant loss of vision in the affected eye.
When corneal conditions cause serious vision problems that can’t be reversed, a corneal transplant often is the best solution. In a corneal transplant, an eye surgeon first removes the diseased or damaged area of the cornea. The removed tissue then is replaced by a section of healthy cornea that has been taken from the eye of a deceased donor.
A corneal transplant involves replacing a diseased or scarred cornea with a new one. When the cornea becomes cloudy, light cannot penetrate the eye to reach the light-sensitive retina. Poor vision or blindness may result.
In corneal transplant surgery, the surgeon removes the central portion of the cloudy cornea and replaces it with a clear cornea, usually donated through an eye bank. A trephine, an instrument like a cookie cutter, is used to remove the cloudy cornea. The surgeon places the new cornea in the opening and sews it with a very fine thread. The thread stays in for months or even years until the eye heals properly (removing the thread is quite simple and can easily be done in an ophthalmologist’s office). Following surgery, eye drops to help promote healing will be needed for several months.
Corneal transplants are very common in the United States; about 40,000 are performed each year. The chances of success of this operation have risen dramatically because of technological advances, such as less irritating sutures, or threads, which are often finer than a human hair; and the surgical microscope. Corneal transplantation has restored sight to many, who a generation ago would have been blinded permanently by corneal injury, infection, or inherited corneal disease or degeneration.