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Stanford Report, March 15, 2000

Implantable contact lenses eliminate hassles of regular contacts  


What's the most irksome part of wearing contact lenses? Scouring the bathroom floor on hands and knees for an errant lens? Waking from a nap to find that a contact has fused to the inside of your eyelid? The monotonous hygienic routine?

Soon, surgically implanted, permanent contact lenses that never need to be removed or cleaned may banish these and other annoyances. Stanford ophthalmologist Edward E. Manche, MD, is participating in a national trial of an implantable contact lens to correct nearsightedness. The lens fits inside the eye, just in front of the pupil.

Stanford is one of 10 sites around the country evaluating these lenses, which have been used in Europe for more than a decade, said Manche, an assistant professor of ophthalmology. Evidence from this round of clinical trials will be submitted to the Food and Drug Administration, which will then decide whether the lenses are safe and effective enough for general use.

The clear, oblong implants are about the size of the tip of your pinky and are made of the same plastic used in replacement lenses for patients with cataracts.

The current trials are testing how well the lenses work in patients with moderate to extreme nearsightedness. Manche said the implants could be particularly useful for people with extreme nearsightedness because their vision problem often is too severe to be corrected with laser eye surgery. They must either wear very thick, distorting glasses, which limit peripheral vision, or resort to contacts, which many people find too bothersome to stick with.

The implant surgery is quick and painless, lasting about 20 minutes. After numbing the eye with anesthetic drops, Manche inserts the lens through a small incision in the cornea -- the clear, dome-shaped "front window" of the eye -- and then centers it over the pupil. A tiny clip at each end of the implant clamps it to the iris, the colored part of the eye. Modeled on a lobster's claw, the clips keep the implant from drifting out of position over time.

Because of the risk of infection, Manche performs the surgery in a sterile operating room in Stanford Hospital. Patients usually receive a mild sedative to reduce anxiety during the operation, and they can go home immediately afterward.

Improvements in vision are usually apparent immediately after the surgery, Manche said. Earlier studies found that 92 percent of patients gained vision of 20/30 or better within a month, Manche said. Vision of 20/20 is considered excellent, while 20/40 is the cutoff for driving a car without wearing corrective lenses.

Besides infection, possible complications include inflammation, increased pressure in the eye and cataracts. Earlier studies have shown that all of these are rare, Manche said. The plastic used to make the implants has a 50-year track record of safe use in the body, he added.

Because the treatment is still considered investigational, only patients who join a clinical trial can obtain it. Volunteers with moderate to extreme nearsightedness -- between - 5 and - 22 diopters on their eyeglass prescription -- are still needed to participate in the trials at Stanford. Patients will have to pay the costs of surgery, around $ 3,500 per eye. For more information, contact Leslie Lyssenko, program director at the Stanford Eye Laser Center, at (650) 498-7020. SR