A penetrating keratoplasty, or corneal transplant, is the surgical removal of a damaged or diseased portion of the cornea and the implantation of a donated human cornea, usually obtained from an eye bank. The cornea is the clear covering of the front of the eye which refracts (bends) light rays as they enter the eye. If the cornea is not shaped properly or becomes clouded, due to injury, infection or disease, and visual acuity is compromised, a corneal transplant may be recommended.
Candidates for PKP
An improperly curved cornea may be corrected surgically for patients whose curvature is too steep or flat to be treated with other methods, or when extensive damage has occurred due to either disease, trauma, infection, or previous surgery.
PKP may be performed on patients with one of the following conditions:
- Corneal edema, ulceration, or dystrophy
- Fuch’s dystrophy, a hereditary condition
- Keratitis or trichiasis
- Pterygia, a benign growth
- Traumatic injury
- Bacterial, fungal, viral, or protozoan infection
- Rejection of a previous graft
Patients whose impaired vision is not treatable with corrective lenses alone may be considered candidates for PKP and put on the corneal transplant list at the local eye bank. It normally takes up to several weeks for appropriate transplant tissue to become available. The donor cornea is screened for any possible diseases, such as AIDS or hepatitis, according to strict FDA regulations.
The PKP Procedure
The PKP procedure may be performed under local or general anesthesia, depending on the patient’s age, condition, and preference. Once the patient is anesthetized, a speculum is used to keep the eyelids open and measurements are taken to assess how much donor tissue is needed. A full-thickness portion of the patient’s damaged tissue is removed and a matching portion of donor tissue is inserted in its place. The new cornea is stitched into place, and the stitches usually remain in place for many months up to one year. The surgery takes 1 to 2 hours and is performed on an outpatient basis.
Risks of PKP
As with any type of surgical procedure, there are certain risks associated with PKP. These risks include:
- Postsurgical Infection
- Leakage from the incision site
- Glaucoma or cataract formation
- Astigmatism, nearsightedness or farsightedness
Visual problems, such as astigmatism, that occur after surgery can be solved with corrective eyeglass or contact lenses. Graft rejection occurs in a certain percentage of cases. Medications are, however, available to prevent or treat corneal rejection. Excessive bleeding can also occur, but is a rare.
Recovery from PKP
Patients should anticipate a slow improvement in their vision after a corneal transplant. It may up to a year for vision to be restored to satisfactory levels. Most patients wear corrective glasses or contact lenses during this period. During recovery, the patient self-administers eye drops and should avoid any possible injury to the eye. This means refraining from sports or other high-risk activities. When the doctor assesses that the sutures are ready for removal, the procedure is simple and is performed right in the doctor’s office.
Patients should report any eye irritation or visual disturbance to the ophthalmologist immediately, since these may indicate that the body is rejecting the donated cornea. Unfortunately, such rejection may occur even years after the operation, so the patient and the doctor must be vigilant. For undetermined reasons, African-Americans are five times more likely to experience a graft rejection.
Approximately 45,000 corneal transplants are performed annually in the United States, and most are successful in restoring vision. Nearly three quarters of penetrating keratoplasty procedures result in grafts that remain effective for at least 10 years.