Eye.com.ph | Corneal Transplantation (Penetrating keratoplasty, corneal graft, PK, PKP)

Cornal transplantion is also known as penetrating keratoplasty, corneal graft, PKP, and PK. It is a surgical procedure to remove the diseased part of the cornea and replace it with a similarly sized and shaped part of a healthy donor cornea.

What are the indications?

Corneal transplantations are performed for several reasons, including the following:

Optical: To improve the optical qualities of the cornea and thus improve vision
- replacing an opaque/scarred cornea due to corneal stromal dystrophy;
- replacing a cornea with irregular astigmatism due to keratoconus.
Reconstructive: To reconstruct the anatomic cornea to preserve the eye
- replacing a perforated cornea.
Therapeutic: To treat a disease unresponsive to medical management to preserve the eye
- as a therapy for a severe, uncontrolled fungal corneal ulcer
- to alleviate pain
  - to relieve the severe foreign-body sensation due to recurrent ruptured bullae in bullous keratopathy.

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How is donor tissue selected?

The Eye Bank Foundation of the Philippines operates the Sta. Lucia Eye Bank at the Sentro Oftalmologico Jose Rizal at the Philippine General Hospital. All donor corneal tissues are processed here.

Tissue matching is not routinely performed or necessary for the majority of corneal transplants. Corneal tissue from donors with the following conditions is not used for transplantation: death from unknown causes, Creutzfeldt-Jakob disease, subacute sclerosing panencephalitis, progressive multifocal leukoencephalitis, congenital rubella, active encephalitis, active septicemia, active endocarditis, active syphilis, viral hepatitis or seropositivity, rabies, HIV seropositivity or high risk for HIV infection, leukemias, active disseminated lymphomas, prior anterior segment surgery or disease, and most intraocular malignancies. The donor's blood is tested for HIV-1, HIV-2, hepatitis B, and hepatitis C. Tissue from donors with positive serology is not used.

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What is the surgical technique?

Corneal transplants can be performed using general or local anesthetic plus IV sedation. To prepare the tissue for transplantation from the donor cornea, the surgeon punches out a corneal button from the central part of the donor cornea using a trephine. To create the recipient bed to receive the donor corneal button, the surgeon removes the central 60 to 80% of the host cornea using a trephine and scissors. The donor corneal button, which is trephined slightly larger than the recipient bed, is then sutured in place.

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What is the postoperative management?

Postoperative topical antibiotics are used for several weeks and topical corticosteroids for several months. In some patients, the corneal astigmatism can be reduced in the early postoperative period by suture adjustment or selective suture removal. Achievement of full visual potential may take up to 1 yr because of changing refraction, slow wound healing, and/or corneal astigmatism. In many patients, earlier and better vision is attained with a rigid contact lens over the corneal transplant. To protect the eye from inadvertent trauma after transplantation, the patient wears shields, glasses, or sunglasses. In addition, patients are advised to avoid bending over completely, lifting heavy objects, straining, or the Valsalva maneuver.

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What are the complications?

Complications include infection (intraocular and corneal), intraocular bleeding, wound leak, glaucoma, graft rejection, graft failure, high refractive error (especially astigmatism and/or myopia), and recurrence of disease, ie, corneal stromal dystrophy.

Graft rejection is not uncommon. Patients complain of decreased vision, photosensitivity, ocular ache, and ocular redness. Graft rejection is treated with corticosteroids, which are administered topically (eg, prednisolone acetate 1% hourly), often with a supplemental periocular injection (eg, methylprednisolone 40 mg). If the graft rejection is severe or if the graft function is marginal, additional corticosteroids are given orally (eg, prednisone 1 mg/kg/day) and occasionally IV (eg, methylprednisolone sodium succinate 3 to 5 mg/kg once). In most non-high-risk grafts, the graft rejection episode is easily reversed, and graft function returns fully. The graft may fail if the graft rejection was unusually severe or long-standing or after multiple episodes of graft rejection. Regraft is possible, but the long-term prognosis for a clear regraft is lower than it was for the original graft.

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What is the prognosis?

The prognosis for a clear, functioning corneal transplant varies by diagnosis. The chance of long-term transplant success is > 90% for keratoconus, corneal scars, early bullous keratopathy, or corneal stromal dystrophies; 80 to 90% for bullous keratopathy or inactive viral keratitis, 50% for active corneal infection, and 0 to 50% for chemical or radiation injury.

The generally high rate of success of corneal transplantation is attributable to many factors, including the avascularity of the cornea and the fact that the anterior chamber has venous drainage but no lymphatic drainage. These conditions promote low-zone tolerance and an active process termed anterior chamber-associated immune deviation, in which there is suppression of intraocular lymphocytes and delayed-type hypersensitivity to transplanted intraocular antigens. Another important factor is the effectiveness of the immunosuppressive drugs used to treat graft rejection.

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CORNEAL TRANSPLANTATION information compiled by Dr. Manolette R. Roque and initially uploaded on February 23, 2006.