Long-term contacts look good in monkeys.

Long-term contacts look good in monkeys

Research with biocompatible polymers and collagen adhesives hints at a new generation of super-extended-wear contact lenses. Researchers are already fitting monkeys with these "almost forever" lenses, which humans may someday wear day and night for years without the risk of corneal damage or infection inherent in today's extended-wear lenses.

Keith P. Thompson of the Yerkes Regional Primate Research Center in Atlanta is experimenting with a technique called laser-adjustable synthetic epikeratoplasty. It involves scraping away the thin outer layer of epithelial cells covering the cornea, then permanently attaching a refractiveM biocompatible corneal covering, or lenticule. The lenticule is made of chemically altered collagen, a naturally occurring protein. Once the lenticule is in place, Thompson uses a laser to fine-tine its curvature for maximum vision correction. Epithelial cells eventually grow over the newly augmented cornea.

Thompson says he's "encouraged" by the results so far, adding that some monkeys have worn the permanent lenses for more than a year. But he says evidence of some erosion of the collagen-based lenses -- probably from enzymes released by surrounding cells -- indicates a need to find better materials. Such materials must be optically clear, laser adjustable, gas permeable, structurally stable and capable of transporting nutrients from inside the eye to the epithelial cells growing outside the lenticule, he notes.

Thompson says he has recently developed enzyme-resistant lenticule materials and collagen-based adhesives that may prove superior to those used in the monkey experiments. He hopes to make sufficient progress within the next few years to obtain FDA approval for safety and stability tests on sightless human eyes.