New techniques for corneal transplantation are associated with improved safety and more rapid visual recovery along with equal or, in some cases, better visual results, says Anthony Aldave, M.D., director of the Cornea Service at UCLAs Jules Stein Eye Institute.
Corneal transplantation, which replaces a patients damaged cornea with donor corneal tissue, is the most common and most successful type of human transplant surgery; approximately 40,000 procedures are performed in the United States each year. The cornea — the clear tissue that forms the front of the eye — can become diseased, affecting vision and requiring transplantation as a result of a variety of conditions, including progressive distortion in the shape of the cornea (keratoconus), scarring secondary to infection or injury, and inherited dysfunction of the corneas inner layer, leading to corneal swelling (Fuchs dystrophy).
Until recently, the procedure of choice for most of these patients was what is called a full-thickness corneal transplant, also known as a penetrating keratoplasty, in which the full thickness of the cornea is replaced, even if only a portion of the cornea is diseased. But several new procedures have emerged that are designed to remove and replace only the affected layer of the cornea.
For patients whose vision is affected by swelling in the corneas inner-most layer, the Descemet stripping endothelial keratoplasty (DSEK) — which involves peeling off the diseased inner layer and replacing it with the inner-most layer from a donor cornea — avoids the astigmatism (irregular shape of the cornea, resulting in blurred vision) commonly associated with full-thickness corneal transplantation. Visual recovery is also more rapid than with a full-thickness transplant, Dr. Aldave says.
By contrast, the deep anterior lamellar keratoplasty (DALK) involves replacing everything but the corneas inner layer. The primary advantage of this procedure, for patients with corneal scarring or keratoconus but with a healthy endothelium (inner layer), is that it eliminates the risk of rejection and failure of the endothelial cells that are critical to keeping the cornea clear. As the patient retains his or her own corneal endothelium, the donor tissue does not need to have a healthy endothelium, and thus the requirements for the donor cornea are less stringent.
The newest approach to corneal transplantation uses a femtosecond laser — the same technology employed for making flaps in LASIK surgery — to produce incisions in the cornea that enable the surgeon to exercise far more precision in what is removed, so that the transplanted tissue fits into the cornea like interlocking pieces of a puzzle. As with the DSEK, this gives us the potential to dramatically decrease postoperative astigmatism because of the precision of the laser, and it strengthens the wound site so that it is more resistant to traumatic opening in the event of eye injury following surgery, Dr. Aldave says.
The news is also good for patients with diseased corneas who are not candidates for transplantation using donor tissue. Instead, some of these patients may be candidates for an artificial-cornea transplant. These are patients who had previously been told there was nothing that could be done for them, Dr. Aldave notes.
With the new approaches, Dr. Aldave concludes, We can now customize corneal transplant surgery for the individual patient, resulting in better outcomes.
www.jsei.org
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