August 18, 1999
Web posted at: 11:45 a.m. EDT (1545 GMT)
Whom it helps
Intacs, tiny transparent rings placed into the cornea's
periphery to reshape the corneal curvature and thus correct vision, were approved by the FDA to treat mild nearsightedness (-1 to 3 diopters) or mild astigmatism (-1 diopter or less) in April.
How it is done
The surgeon chooses which of the three approved sizes of
polymer crescents is correct and makes a 1 millimeter incision in the periphery of the cornea, rotating the half-circle rings into place. Intacs are meant to be permanent but can be removed, says Assil, who served as a clinical investigator for Intacs. Because they are inserted below the nerve endings of the cornea, the rings are not felt when in place, according to KeraVision Inc., the manufacturer.
In the clinical studies, about 75 percent of patients had 20/20
vision after the procedure, according to KeraVision, and more than half had even better than 20/20. In all, 97 percent saw at least 20/40 with Intacs -- good enough in most states to drive without corrective lenses.
What can go wrong
About 5 percent of the clinical study patients requested
removal of the Intacs, says Mick Taylor, a spokesman for KeraVision, with about half citing problems with glare or seeing halos around lights and the other half complaining of under- or overcorrection.
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