OPTICAL PROSTHETIC: New miniature telescopelike devices implanted in patients' damaged eyes may halt and even reverse vision loss caused by age-related macular degeneration. Image: VisionCare Ophthalmic Technologies, Inc.
Those suffering from advanced stages of macular degeneration may by the end of this year be able to halt and even reverse vision loss caused by the age-related eye disease. If, that is, the Food and Drug Administration (FDA) gives ophthalmologists the green light to implant new miniature telescopelike devices in patients' damaged eyes.
The optical prosthetics, tiny enough to be balanced on a fingertip, dramatically improved the vision of about two thirds of the 206 patients studied in a 24-month clinical trial, according to a new study published in Archives of Ophthalmology.
"This is a good device and it offers hope for people with no other options," says lead author Kathryn Colby, an ophthalmologist and director of the Joint Clinical Research Center at the Massachusetts Eye and Ear Infirmary in Boston. There is no known treatment to correct macular degeneration; until now physicians have focused on trying to reduce the risk of the disease and keep it in check with laser treatment, eyewear with special magnifying capabilities, and nutritional supplements including antioxidants and zinc.
Age-related macular degeneration affects more than 1.75 million Americans, a number projected to climb to almost three million by 2020 thanks to the country's rapidly aging population, according to the U.S. National Institutes of Health's National Eye Institute. Macular degeneration is a disorder of the central retina, or macula, that causes the afflicted person to see a dark spot in the center of his or her field of vision, impairing the ability to read, recognize faces and watch TV.
The implantable mini-scope, developed by Saratoga, Calif.-based VisionCare Ophthalmic Technologies, works with the eye's cornea like a telephoto system, rendering an enlarged retinal image designed to reduce the area of diminished vision. Once implanted, the device protrudes 0.1 to 0.5 millimeter beyond the surface of the pupil but does not touch the corneal endothelium, a layer of cells lining the back of the cornea.
This is not an easy fix, however, and surgeons are developing special techniques to properly and swiftly implant the device without damaging the eye. The device is a compound telescope system that consists of a glass cylinder that is 4.4 millimeters in length and 3.6 millimeters in diameter and houses wide-angle micro-optics.
The cylinder fits into a one-piece polymethylmethacrylate case with two rigid polymethylmethacrylate haptics that protrude like tiny arms and hold the device in place behind the eyeball's natural lens. Polymethylmethacrylate is a clear plastic that is traditionally used as a shatterproof replacement for glass in places such as hockey rinks and large aquariums. The tiny telescope is virtually undetectable because it is implanted inside the eye, and mostly covered by the iris, the colored portion of the eye.
During a 24-month clinical trial, Colby (and fellow ophthalmologists David Chang of the University of California, San Francisco, Doyle Stulting of Emory University's Eye Center in Atlanta, and Stephen S. Lane of Associated Eye Care in Stillwater, Minn.) developed and tested a preferred technique for implanting the device to most effectively treat bilateral end-stage macular degeneration, which most commonly afflicts people over the age of 55. The device can treat either form of age-related macular degeneration: the dry stage, where the delicate tissues of the macula become thinned and slowly lose function, or the less common wet stage that's caused by the growth of abnormal blood vessels behind the macula.