WHAT IS THE CORNEA?
The cornea is the clear part of the eye that covers the pupil. Just like a clear window, the cornea is critical in maintaining a sharp focus on objects. The inside layer of cornea, the endothelium, has a finite number of cells that maintain clarity and do not regenerate. The epithelium, the outside layer of the cornea, has cells that re-generate every 5-7 days - just like your skin.
WHAT DAMAGES A NORMAL CORNEA?
Conditions that cloud the cornea or disrupt the smooth surface will greatly impact how clearly a person sees. Infections, injuries, and some ocular diseases can cause scarring that make the cornea more opaque. Common causes include Fuchs' dystrophy and keratoconus. Fuchs' dystrophy is an accelerated aging of the endothelium. The finite number of cells age and die at a rapid rate causing corneal swelling. Keratoconus is a thinning and cone-like formation of the cornea that causes irregularities in the way the cornea focuses. Corneal decompensation can occur after cataract surgery although this is a rare problem. These corneal diseases can often be treated with medications or contact lenses, but if these measures fail to improve the vision, a cornea transplant may be needed.
HOW SUCCESSFUL IS CORNEAL TRANSPLANTATION?
Approximately 40,000 corneas are transplanted yearly in the United States. Success defined as clarity and acceptance by the body's immune system is about 90%. Visual improvement may be limited by other eye disease. Nevertheless, the vast majority of patients regain useful vision after corneal transplantation. Because the cornea usually has no blood vessels in it, it is considered an immune privileged tissue. This is in contrast to kidneys and lungs which have a higher graft rejection rate, and require strong systemic immune suppression. Usually only eyedrop steroids are needed to prevent rejection.
HOW ARE DONOR CORNEAS OBTAINED? IS THERE A LONG WAITING LIST?
Donor corneas are harvested from people after consent is obtained within 12 hours after death. The tissue is closely inspected by eye-bank personnel under a powerful microscope. Blood from the donor is tested for any communicable diseases such as hepatitis and AIDS. The cornea is offered only if all blood tests are negative. The corneal tissue is kept in cold storage and must be used within six days from death. Matching blood type is not necessary for corneal transplantation.
The eye-banks can usually find tissue for patients if the surgery is scheduled one to two months in advance due to a predictable number of donors per week. Emergency tissue is readily found in rare cases when it is needed. We are very lucky in this country to have a steady supply of concerned citizens donating their eyes after death.
WHAT IS THE SURGERY AND RECOVERY LIKE?
Surgery is performed at the outpatient facility, and typically takes about 60 to 90 minutes. At pre-op the eye and the lids are anesthetized locally. Patients are sedated but are breathing on their own, and often sleep through the surgery. Due to anesthesia, the surgery is painless. Following surgery, the eye is patched overnight. The following day, the patch is removed, and the eye is examined. Eye drops are started and continued for months but in decreasing doses. Some scratchiness and soreness is normal the first few weeks, and no heavy lifting or bending over past the waist is allowed while healing begins. Visual rehabilitation takes quite a long time with this surgery and comes in small incremental steps. Final vision is often not achieved for nine to twelve months from the time of surgery. Sometimes temporary glasses can be used at six months. Patients can often return to work one to two weeks after surgery.