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Cincinnati-"Regardless of whether we are talking about full-thickness transplants or endothelial transplants, corneal transplant rejection is the leading cause of graft failure," said Edward J. Holland, MD, director, Cornea and External Diseases, Cincinnati Eye Institute, Cincinnati.
He pointed out that for routine penetrating keratoplasty, there is an endothelial rejection reaction in 20% to 25% of patients, and 5% to 10% of the grafts fail as a result of the reaction. The failure rate is even higher in immunologic high-risk keratoplasty, with 25% to 50% of grafts failing because of rejection.
Factors in graft failure
"If there are two or more quadrants of stromal neovascularization, this increases the risk of rejection," he stated.
In addition, the size of the graft is instrumental and previously was thought to influence graft failure. Dr. Holland explained, however, that he prefers using large grafts, but he circumvents the effects of a large graft by treating the patients more aggressively with steroids early in the postoperative period. Topical cyclosporine has also helped prevent graft failure.
"The risk of graft rejection has not limited me from using large grafts, and I believe that better vision is achieved with large grafts," he said.
Patient age is another factor that increases the risk of rejection. Pediatric patients offer the biggest challenges.
"Children have a more efficient immune system than adults," he added. "In addition, we do not have the ability to examine the patient adequately nor can we depend on patient input about symptoms of rejection."
"The factors that incite a graft rejection reaction postoperatively are anything that causes inflammation of the anterior segment or induces graft neovascularization," he said. "Patients who develop broad peripheral anterior synechiae with the iris vessels of the cornea are at risk of rejection."
In his practice, any type of manipulation of the graft, such as might occur with extensive suture removal, a keratorefractive procedure such as a relaxing incision, a trabeculectomy, or cataract surgery, seems to be associated with development of graft rejection reaction.
Types of rejection reactions
There are different types of graft rejection reactions depending on the type of procedure performed.
With penetrating keratoplasty, the epithelial layer, the subepithelial area, the stroma, and the endothelium independently or together can be rejected.