Penetrating keratoplasty (PKP), also referred to as a corneal transplant or corneal graft, is the surgical removal of a damaged or diseased portion of the cornea, followed by the implantation of healthy tissue from a donated human cornea, which is usually obtained from an eye bank. The cornea is the clear covering of the front of the eye that refracts (bends) light rays as they enter the eye. If visual acuity is compromised because the cornea is not shaped properly or is clouded from injury, infection or disease, PKP may be recommended. The cornea has five layers; during PKP, all five layers are replaced with donor tissue.
Candidates for Penetrating Keratoplasty
An improperly curved cornea may be corrected surgically for patients whose curvature is too steep or too flat to be treated with other methods, or when there is extensive damage from 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
A patient whose impaired vision is not treatable with corrective lenses alone may be considered a candidate for PKP, and put on a corneal-transplant waiting list at a local eye bank. It usually 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 U.S. Food and Drug Administration regulations.
The Penetrating Keratoplasty Procedure
The PKP procedure is performed, depending on the patient's age, condition and preference, under local or general anesthesia. 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. The damaged tissue is removed, and a matching portion of donor tissue is inserted in its place. The new tissue is stitched into place; stitches usually remain in place for many months up to a year. The surgery takes 1 to 2 hours, and is performed on an outpatient basis.
Risks of Penetrating Keratoplasty
As with any type of surgical procedure, there are certain risks, including the following, associated with PKP:
- Postsurgical infection
- Leakage from the incision site
- Glaucoma or cataract formation
- Astigmatism, nearsightedness or farsightedness
Vision problems, such as astigmatism, that occur after surgery can be addressed with corrective eyeglass or contact lenses. Graft rejection occurs in a certain percentage of cases. Medications are available, however, to prevent or treat corneal rejection. Excessive bleeding can also occur, but it is rare.
Recovery from Penetrating Keratoplasty
Patients should anticipate a slow improvement in vision after PKP. It may take 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. Removal of sutures is a simple in-office procedure.
A patient should report any eye irritation and vision issues to the ophthalmologist immediately; they may indicate that the body is rejecting the donated cornea. Unfortunately, rejection can occur even years after surgery, so patient and doctor must be vigilant. For undetermined reasons, African-Americans are five times more likely to experience a graft rejection.
Approximately 45,000 PKPs are performed annually in the United States, and most are successful in restoring vision. Nearly three-quarters of PKPs result in grafts that are effective for at least 10 years.