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Implanted
Plastic Ring Shows Promise for Correcting Nearsightedness Preliminary results of a new surgical procedure, called "corneal ring implantation,” to correct nearsightedness, are promising, according to the UCSF eye specialist who is heading a clinical trial of the technique.
Richard Abbott, MD, UCSF professor of ophthalmology, presented the findings at a media briefing at the American Academy of Ophthalmology annual meeting in San Francisco Tuesday. He is principal investigator of an FDA-approved national trial. In corneal ring implantation, which is short for the full medical name intrastromal corneal ring segment implantation, a tiny plastic ring is surgically inserted into the periphery of the cornea, the delicate eye tissue that covers the iris and pupil. The cornea is the window through which light is transmitted and focused on the retina. In nearsighted people, the tissue has an unusually steep curvature, which forces light rays to focus in front of the retina, instead of directly on it, as it should. The corneal ring is intended to flatten, or correct, the curvature. In early results of the FDA-approved, phase III clinical trial, 97 percent of 113 patients had improved vision of at least 20/40, the threshold for driving a car without glasses. Nearly half had better than 20/20 vision. All of the patients had mild to moderate cases of nearsightedness. "These results show equal, or superior to, outcomes to those achieved with laser-correction procedures," says Abbott, co-director of the UCSF Vision Correction Center. Significantly, the procedure is the first surgical technique for nearsightedness that does not involve removing eye tissue, according to Abbott. While the ring is designed to remain permanently in the eye without maintenance, it can be removed by a surgeon. "This allows people to go back to glasses or contacts," he says. "Theoretically, it could allow a surgeon to replace the rings as the patient's eyesight changes with age, or to take advantage of future advances in vision correction." The UCSF Department of Ophthalmology is one of 10 sites in the United States--and the only one in Northern California--participating in the clinical trial. The ring procedure has already received regulatory approval for the 15 European Union Nations. Smaller and lighter than hard contact lenses, the corneal ring is made of the same medical plastic that has been safely used for more than 40 years in cataract patients. The surgery is performed under a topical anesthetic and is usually completed in under half an hour as an outpatient procedure. Visual improvement usually begins within a day after surgery, according to Abbott. By Jennifer O’Brien See yesterday’s Daybreak stories: Cultivations in Lab May Usher in New Era for Corneal Transplants New Laser Good for Severe Eye Corrections, Preliminary Studies Show 1st appeared 10/30/97 |
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