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Indications: Corneal transplantations are performed for several reasons:

• To reconstruct the cornea (eg, replacing a perforated cornea)
• To relieve intractable pain (eg, severe foreign body sensation due to recurrent ruptured bullae in bullous keratopathy)
• To treat a disorder unresponsive to medical management (eg, severe, uncontrolled fungal corneal ulcer)
• To improve the optical qualities of the cornea and thus improve vision (eg, replacing a cornea that is scarred after a corneal ulcer, is clouded because of edema as occurs in Fuchs' dystrophy or after cataract surgery, is opaque due to deposits of nontransparent abnormal corneal stromal proteins as occurs in hereditary corneal stromal dystrophy, or has irregular astigmatism as occurs with keratoconus)

The most common indications are the following:

• Bullous keratopathy (pseudophakic or aphakic, Fuchs' endothelial dystrophy)
• Keratoconus
• Repeat graft
• Keratitis or postkeratitis (caused by viral, bacterial, fungal, or Acanthamoeba infection or perforation)
• Corneal stromal dystrophies.

Procedure: Tissue matching is not routinely performed. Cadaveric donor tissue cannot be used from anyone suspected of having a communicable disease.

Corneal transplantation can be performed using general anesthesia or local anesthesia plus IV sedation.

Topical antibiotics are used for several weeks postoperatively and topical corticosteroids for several months. To protect the eye from inadvertent trauma after transplantation, the patient wears shields, glasses, or sunglasses. If transplantation involves the full thickness of the cornea (as in penetrating keratoplasty or PKP), achievement of full visual potential may take up to 18 mo because of changing refraction with wound healing and after suture removal. If only the endothelium is replaced (as in Descemet's stripping endothelial keratoplasty), achievement of full visual potential usually occurs by 6 mo. In many patients, earlier and better vision is attained by wearing a rigid contact lens over the corneal transplant.

Complications: Complications include all of the following:

• Graft rejection
• Infection (intraocular and corneal)
• Wound leak
• Glaucoma
• Graft failure
• High refractive error (especially astigmatism, myopia, or both)
• Recurrence of disease (with herpes simplex or hereditary corneal stromal dystrophy).

Graft rejection rates are usually < 10% but may be up to 68% in higher-risk patients. Rejection symptoms include decreased vision, photosensitivity, ocular ache, and ocular redness. Graft rejection is treated with topical corticosteroids (eg, prednisolone Some Trade Names
ORAPRED
PRELONE
Click for Drug Monograph
1% hourly), sometimes with a supplemental periocular injection (eg, triamcinolone Some Trade Names
ARISTOCORT
KENACORT
KENALOG
NASACORT
Click for Drug Monograph
acetonide 40 mg). If graft rejection is severe or if graft function is marginal, additional corticosteroids are given orally (eg, prednisone Some Trade Names
DELTASONE
Click for Drug Monograph
1 mg/kg once/day) and occasionally IV (eg, methylprednisolone Some Trade Names
MEDROL
Click for Drug Monograph
3 to 5 mg/kg once). Typically, the rejection episode reverses, and graft function returns fully. The graft may fail if the rejection episode is unusually severe or long-standing or after multiple episodes of graft rejection. Regraft is possible, but the long-term prognosis is worse than for the original graft.

Prognosis

The chance of long-term transplant success is

• > 90% for keratoconus, corneal scars, early bullous keratopathy, or hereditary corneal stromal dystrophies
• 80 to 90% for more advanced bullous keratopathy or inactive viral keratitis
• 50% for active corneal infection
• 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 (an immunologic tolerance that results from constant exposure to low doses of an antigen) and a process termed anterior chamber–associated immune deviation, in which there is active suppression of intraocular lymphocytes and delayed-type hypersensitivity to transplanted intraocular antigens. Another important factor is the effectiveness of the corticosteroids used topically, locally, and systemically to treat graft rejection.

Corneal Limbal Stem Cell Transplantation

Corneal limbal stem cell transplantation surgically replaces critical stem cells at the limbus (the area where the conjunctiva meets the cornea). Host stem cells normally reside in this area. Transplantation is done when the host stem cells have been too severely damaged to recover from disease or injury.

Conditions such as severe chemical burns, Stevens-Johnson syndrome, and severe contact lens overwear may cause persistent nonhealing corneal epithelial defects. These defects result from failure of corneal epithelial stem cells to produce sufficient epithelial cells to repopulate the cornea. If untreated, persistent nonhealing corneal epithelial defects are vulnerable to infection, which can lead to scarring, perforation, or both. Under these circumstances, a corneal transplant, which replaces only the central cornea and not the limbus, is insufficient; stem cells are needed to produce new cells that repopulate the cornea, restoring the regenerative capacity of the ocular surface.

Corneal limbal stem cells can be transplanted from the patient's healthy eye or from a cadaveric donor eye. The patient's damaged corneal epithelial stem cells are removed by a partial-thickness dissection of the limbus (ie, all the epithelium and the superficial stroma of the limbus). Donor limbal tissue, which is prepared by a similar dissection, is sutured into the prepared bed.

Last full review/revision October 2008 by Melvin I. Roat, MD

Content last modified October 2008