Types of transplant Corneal transplants are among the most straightforward and successful of all transplant procedures because the cornea is easily accessible to the surgeon and has no blood vessels. There are two basic types of transplant. One replaces the full thickness of the cornea. The other selectively replaces either the inner or outer layer of the cornea.
Finding transplantable corneas Corneal transplants depend on donated corneas. Minnesota Lions Eye Bank obtains and distributes donated eye tissue for use in corneal transplants, medical research, and medical education. To find out how your corneas can restore sight and renew life after you no longer need them, visit www.mnlionseyebank.org.
Full thickness Traditionally, corneal transplantation required replacing the cornea’s full thickness. This procedure is still done when necessary and is called a penetrating keratoplasty (PK). In this procedure, the central part of the cornea is removed using a trephine, which is similar to a very small cookie cutter. The donor cornea is then sutured (sewn) into place. This surgery lasts about one to two hours, is performed in an operating room, and the patient goes home afterward. It may take up to one year before sutures can be removed but they are thinner than a human hair and do not cause irritation. Recovery of vision can also take many months and patients may have a significant change in eyeglass prescription or may require contact lenses posttransplant. Partial thickness Techniques developed in recent years permit transplanting either inner or outer layers of the cornea. These partial thickness transplants have the general name of lamellar keratoplasty. More specific names are given to these procedures depending on which layer is transplanted. Endothelial keratoplasty (EK) replaces the inner layer of the patient’s cornea with a donated inner layer that contains endothelial pump cells. EK might be performed for a patient with corneal swelling caused by malfunctioning or insufficient numbers of endothelial pump cells, as in Fuchs’ dystrophy. In this procedure, surgery is performed through a very small incision on the side of the eye. It involves Corneal removing the patient’s damaged tissue from the inner part of the transplants cornea, placing the inner part of the have an donor cornea into the patient’s eye, and moving the donated layer into excellent position using an air bubble. track record. The bubble holds the partial transplant in place, so there are no sutures in the transplant. Pumping action of the new cells causes the transplant to completely adhere and reduces corneal swelling. The bubble is absorbed by the eye within a few days. Endothelial keratoplasties heal much faster than penetrating keratoplasties. An EK wound is far less likely to rupture if the eye subsequently suffers an injury during or after healing because the EK incision is significantly smaller than the one used for PK. And, since EK preserves the outer parts of the patient’s cornea, this procedure may not change the patient’s eyeglass prescription as signifi-
cantly as a full-thickness transplant would. Deep anterior lamellar keratoplasty (DALK) replaces damaged stroma while preserving the patient’s inner corneal layers. Since the inner layers are kept intact, the eye is not completely opened during the surgery, which enhances the safety of this procedure. The patient’s own endothelial cells are also preserved, which reduces the chance of transplant rejection. DALK sutures may be removed sooner than those used for PK.
Reduce your risk Although corneal transplant is a safe and commonly performed surgery, it’s prudent to reduce the risk of eventually needing it. To do so, see your eye doctor regularly to detect any conditions at an early stage, wear eye protection when using tools, follow established protocol if you use contact lenses, and contact your doctor promptly about eye infections, especially if you wear contact lenses. Omar Awad MD, FACS, is a board-certified ophthalmologist who specializes in corneal diseases, cataracts, and refractive surgery. Dr. Awad performs corneal transplants at the Phillips Eye Institute in Minneapolis and practices with Awad Eye Care, LLC, in St. Paul and with LasikPlus in Maple Grove, Edina, and Oakdale.
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