Artificial Corneal Transplants Giving Some Patients Hope
Monday, June 16, 2003
For patients who have undergone unsuccessful corneal transplants and have little or no sight, surgeons at Strong Memorial Hospital are now offering hope in the form of an artificial cornea. The device in some cases can offer limited vision, allowing patients to see shadows, movement and colors, and some may even regain the ability to read.
James Aquavella, M.D., professor of ophthalmology at the University of Rochester Eye Institute, is studying a new, flexible, one-piece artificial cornea (keratoprosthesis) designed to replace scarred or diseased corneas. The device is easier to implant than older models, cutting down on surgery time and requiring no stitches or donor tissue. The new procedure offers significantly more possibilities for patients at no more risk than implanting a cadaveric graft.
“It is our expectation that for patients with a high risk of failure with a traditional corneal transplant, or as in this study for patients who have already failed two previous attempts at corneal transplantation, this option offers renewed hope,” Aquavella says.
“In more than 35 years of involvement in corneal research and surgery, I have witnessed the introduction of numerous techniques and devices,” he adds. “In keratoprosthesis work, these have been associated with very long, invasive and complicated surgical procedures with the prospect for only incremental improvement. This new development presents a fresh way of approaching the surgical and biological problems.”
After having implanted more than 100 artificial cornea devices, and working with the new Argus implant in his surgical laboratory, Aquavella is joining investigators from 26 eye centers around the world to evaluate the device. The University of Rochester Eye Institute has been designated one of six Centers of Excellence in the United States to assist with the development of the technology. While the actual device has the approval of the FDA, Aquavella and colleagues will track complications, visual acuity, medications and failure rate. The first three Alpha Cor cases at the University of Rochester Eye Institute are scheduled for Tuesday, with plans to perform up to 20 cases this year to gather data.
The surgery is similar to implanting a donor cornea. Part of the cornea is removed and the AlphaCor is transplanted in its place. The artificial cornea, about the size and thickness of a nickel, is held by a ring of host tissue, which alleviates the incidence of rejection. The procedure concludes with the formation of a flap of tissue from the conjunctiva (the white of the eye), which is used to cover the surface of the eye. This natural bandage allows the AlphaCor to heal in place.
Three months after surgery, a circle of tissue covering the front of the eye is removed, allowing light and images to enter. The patient sees through this opening, and the vision should be as good as the health of the back of the eye will allow. Some vision may be improved with glasses or even with contact lenses fit over the prosthesis.
Corneal transplants using cadaveric donors have been around since the 18th century. Because early outcomes were generally unsuccessful – a high incidence of rejection existed – researchers began experimenting with plastic corneas in the 1950s and 1960s as a way to help more patients with severely damaged corneas.
Aquavella began implanting devices in New York before continuing his work in Rochester in the late 1960s. The procedures were long and tedious, and results were not known for many months. Patients required careful follow-up for the rest of their lives in an attempt to reduce the ever-present danger of serious complications.
“This Argus device is easier to implant, and much smaller,” he says. “The recovery time is faster, with fewer complications, and often vision is re-established in just three months.”
The relative ease by which surgeons can treat patients with the Alpha Cor could have an enormous impact on vision care in the Third World, where countries experience a high rate of corneal blindness as a result of exposure to the sun, disease, genetics and poor nutrition, Aquavella says. Without the need for donor corneal tissue, which is in very limited supply in the underdeveloped countries of Asia, Africa, and to some extent South America, surgeons could treat many more cases of corneal blindness.
Corneal blindness affects more than 10 million people worldwide, yet only 100,000 people receive corneal transplants each year. The shortfall is due to a combination of inadequate supply of donor corneas and the unsuitability of some patients to receive a corneal graft. While traditional corneal transplants are associated with a success rate of more than 80 percent today, the body has a capacity to reject human donor tissue, and a number of people with corneal blindness have a poor prognosis for success.