A new review article in the June issue of Focal Points, a monthly publication of the American Academy of Ophthalmology, calls keratoprosthesis a viable alternative to standard corneal transplantation to help people suffering from corneal blindness. Co-authored by Rony R. Sayegh, MD, an eye surgeon with the University Hospitals Eye Institute, the paper states that while standard corneal transplantation is successful in treating many of the 8 million cases worldwide of corneal blindness, keratroprosthesis is an important alternative when the standard treatment fails.
"There is no question that keratoprosthesis has helped restore vision in many patients blinded by corneal disease," said Dr. Sayegh, who also is an Assistant Professor of Ophthalmology at Case Western Reserve University School of Medicine, who co-authored the paper with Natalie A. Afshari, MD, Professor of Ophthalmology and Chief, Division of Cornea and Refractive Surgery of the Shiley Eye Center, University of California, San Diego, La Jolla, California. A keratoprosthesis is a surgical device that is assembled with a donated cornea, then is transplanted replacing severely damaged or diseased corneas. The surgery is relatively rare and is performed to restore vision in patients suffering from severely damaged corneas due to congenital birth defects, infections, inflammation, chemical injuries and burns.
The most widely used device for this procedure in the United States is the Boston keratoprosthesis (Boston KPro). It consists of a clear plastic front plate with a stem, which houses the optical portion of the device, a back plate, and a titanium locking ring. Annually, only about 600 patients in the United States receive a KPro compared with 36,700 corneal transplants nationwide.
"The KPro is reserved for a small but important number of people who are blinded by severe corneal conditions," said Dr. Sayegh. "If a patient undergoes several standard cornea transplantations, unhealthy blood vessels can develop leading to rejection of the transplanted cornea, which makes it impossible to keep further standard transplants clear for vision. The Boston KPro and other prostheses can give these people a last chance to have their sight restored and be able to function independently again."
Dr. Sayegh recently began testing a new design for the K-Pro which has a back plate made of titanium that assembles via a new clicking mechanism for the back plate to hold onto the front plate, obviating the need for an additional locking ring.
"The newer design eliminates an added piece and makes it easier for the surgeon to assemble the device," said Dr. Sayegh. "More importantly, less components may translate into improved overall safety of the procedure, and it is likely that this updated design will become the new standard."
Many members of the cornea service at University Hospitals have researched and contributed to the development of the Boston keratoprosthesis. The availability of this technique to the Northeast Ohio residents has helped a number of patients regain vision after many years of blindness.
Dr. Sayegh said that there are other types of keratoprotheses available, and which one a surgeon chooses should depend on the needs of the patient and the severity of his or her condition.
"The more successful devices tend to have a wider range of indications, cost less, and are easier to implant surgically, preferably in a single step, by a single surgeon, and employing techniques familiar to most surgeons. Good anatomic retention and ability to restore the best achievable visual potential are other important factors for the success of a keratoprosthesis. Finally, a favorable safety profile with a low occurrence of complications, particularly sight-threatening ones, is of the essence. Clinicians should be able to recognize suitable candidates for the procedure, and the choice of which keratoprosthesis to use must be tailored to the patient's specific condition," he said.