A cornea transplant, also known as keratoplasty or a corneal graft, replaces damaged tissue on the clear front surface of the eye.
When disease or injury damages the cornea, eyesight is affected. The light that enters the eye becomes scattered, resulting in blurred or distorted vision. When the cornea is extremely scarred or damaged, a corneal transplant is needed to restore functional vision.
Keratoplasty is performed routinely and is regarded as the most successful of all tissue transplants. According to the National Keratoconus Foundation, over 40,000 cornea transplants are done annually in the United States.
In recent years, an innovative type of corneal transplant has gained popularity. Known as Descemet’s Stripping Endothelial Keratoplasty (DSEK), this new procedure removes a smaller and thinner portion of the cornea. In 2009, DSEK was declared by the American Academy of Ophthalmology as superior to the conventional surgery because it may provide better vision outcomes and more eye stability. It is also associated with less risk factors. However, when the majority of the cornea is damaged, a more comprehensive removal may still be necessary to facilitate a successful transplant.
Criteria for a Corneal Transplant
A multitude of reasons indicates candidacy for a corneal transplant. Possible reasons include:
- Eye diseases, such as keratoconus
- Complications from laser surgery, such as LASIK
- Extreme inflammation on the cornea
- Scarring as a result of infections, such as eye herpes or fungal keratitis
- Thinning of the cornea and an irregular shaped cornea
- Hereditary factors
- Corneal failure due to previous surgical procedures
- Chemical burns or injuries that damaged to the cornea
Cornea Transplant Procedure
Once a patient has been recommended and approved for a corneal transplant to restore vision, the patient’s name is added to a list at an eye bank. The United States has a very advanced eye bank system, and the general wait time for a donor's eye is one to two weeks. The tissue of donor corneas is checked for clarity and screened meticulously for disease before it is released for transplant.
The actual surgery is generally performed as an outpatient procedure that does not require hospitalization. General or local anesthesia may be used, depending upon the patient’s preference, age, and health condition. Local anesthesia is injected into the skin surrounding the eye, which relaxes the muscles that control movement and blinking. Eye drops numb the eye itself.
Once the anesthesia has taken effect, the surgeon inspects and measures the damaged corneal area in order to decide upon the size of the transplantation. Eyelids are held open during this time. The surgeon then removes around a button-shaped piece of the corneal tissue and replaces it with a nearly identical sized button of donor tissue. The new, healthy tissue is sutured into place. The entire procedure takes approximately one to two hours.
Following the surgery, a plastic shield must be worn over the eye in order to protect it against any inadvertent bumps or rubbing.
Rejection of the Corneal Graft
Although the vast majority of cornea transplants are successful, sometimes the new tissue is rejected. Warning signs of rejection include:
- Extreme sensitivity to light
- Decreased vision
These symptoms may be experienced as soon as one month after the surgery, or as delayed as five years later. Medications can be prescribed to reverse the rejection process. If the corneal graft fails completely, the transplant can be repeated and the outcome is generally positive. Yet the total rejection rates do increase with the total number of corneal transplants.
Recovery and Healing
It can take up to a year or longer to heal completely from a corneal transplant. At the beginning, vision is blurry and the transplant site is often swollen and thicker than the rest of the cornea. As vision returns, patients are able to return to normal daily tasks and most people can return to work within three to seven days after surgery. However, heavy lifting and exercise must be avoided for the first few weeks.
To help the body accept the corneal graft, steroid eye drops must be applied for several months. A pair of eyeglasses or a protective shield must also be worn for eye safety. Depending upon the health of the eye and the healing rate, stitches may be removed at any time from three months to more than a year later. Astigmatism often occurs as a result of an irregular corneal surface, and adjustments may be made to the sutures around the new cornea in an effort to reduce this problem.
Vision after a Cornea Transplant
Vision improvement after a cornea transplant is a process that can last up to one year later. Eyeglasses or contact lenses must be worn immediately after the surgery since the curvature of the corneal transplant will not precisely match the natural corneal curve.
When healing is complete and stitches are removed, laser surgery may be indicated to correct vision. LASIK or PRK are both procedures that can help decrease dependence on eyeglasses or contacts. An irregular corneal surface may point to the need to wear rigid gas permeable (GP) contact lenses for vision correction.