"Preconditioning" The Cornea: A New Key To Transplant Success?

Main Category: Eye Health / Blindness
Also Included In: Transplants / Organ Donations
Article Date: 02 Jul 2010 - 2:00 PDT

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Although it is already one of medicine's most successful transplant procedures, doctors continue to seek ways to improve corneal transplants. A new report by German and British researchers shows that transplanted corneas are more likely to fail or be rejected in patients whose eyes exhibit abnormal vessel growth, called corneal neovascularization, before surgery. The team's meta-analysis of recent studies appears in July Ophthalmology, the journal of the American Academy of Ophthalmology. Their findings also suggest a new treatment that could improve transplant success rates.

Claus Cursiefen, MD, and colleagues reviewed 19 studies involving nearly 24,500 corneal transplants (called "grafts"). The cornea is the eye's clear outer surface that provides much of the visual power.

"The presence of corneal neovascularization before surgery makes it about 30 percent more likely that the transplant will fail, and more than doubles the risk of graft rejection," said Dr. Cursiefen. "We also found that the risks of failure and rejection rise with the extent of vascularization - the more extensive it is, the higher the risks."

This implies that patients who have corneal neovascularization might benefit from treatment before transplant surgery with growth-inhibiting drugs (antiangiogenics) such as bevacizumab or ranibizumab, or with another type of drug that works at the level of gene transcription to discourage vessel growth; one such drug, GS101, is now in clinical trials. This "preconditioning" approach is worthy of thorough testing and assessment, the researchers say.

"Preconditioning may prove to be a useful strategy to promote survival of the graft," Dr. Cursiefen said.

More than 40,000 transplant surgeries are performed annually in the United States to restore vision in people whose corneas have been damaged by injury or illness-it is the most common type of tissue transplant. Patients with nonvascular corneas have a high chance of success: up to 81 percent of such transplants remain healthy at five-year follow up.

Ophthalmologists (Eye M.D.s) use several pre-surgery measures to enhance success rates, such as matching cornea donor and recipient tissues as closely as possible and suppressing the immune response in the person receiving the graft. After transplants doctors monitor patients closely for signs of failure and treat early and aggressively if warning signs appear.

Dr. Cursiefen's review found that increasing age and male gender appear to be additional, independent risk factors for graft failure, but not for graft rejection; he says further study is needed to confirm these findings. In June 2009 (Ophthalmology) the Cornea Donor Study reported lower rates of corneal transplant success in patients who had corneal edema (swelling) after surgery for cataract removal and intraocular lens implantation, and in glaucoma patients.

Source:
American Academy of Ophthalmology

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