August 18, 1999
Web posted at: 11:45 a.m. EDT (1545 GMT)
Whom it helps
LASIK is ideal for correcting moderate to high levels of nearsightedness (up to about -12 diopters, or about 20/800), farsightedness (about 4 diopters) and astigmatism (about 4 diopters), in which the irregular shape of the cornea causes blurry vision.
How it is done
Using a surgical instrument called a microkeratome, the
surgeon shaves off a thin, hinged flap of cornea (the transparent tissue covering the front of the eye). With the flap out of the way, the surgeon uses an excimer laser to reshape the underlying cornea, with the exact number of laser pulses predetermined by the computer. After the specified number of pulses, the doctor gently lays down the flap, which settles back onto the eye without stitches. The excimer laser used in LASIK has thus far been approved only for PRK (photorefractive keratectomy) by the FDA, but an advisory panel to the FDA recently advised the agency to approve it for LASIK as well. Doctors who perform LASIK with the excimer laser are using it in an off-label but legal manner.
Overall, about 90 percent of LASIK patients can get by without
glasses or contact lenses about 90 percent of the time, says Dr. Peter Hersh, director of The Cornea and Laser Eye Institute at Hackensack (New Jersey) University Medical Center and chief of cornea and refractive surgery at the UMDNJ-New Jersey Medical School. Those who are old enough to have presbyopia, the age-related decline in ability to focus on near objects that begins around age 40, will still have to wear reading glasses unless they undergo a technique called "surgical monovision,'' in which one eye is corrected for distance and the other for near objects.
What can go wrong
There can be less-than-perfect vision, haze, halo effects and glare. If your pupils are large (5 millimeters or more), some doctors say you may be more likely to have problems with the halo and glare effects, especially as pupils widen in darkness and cross the edge of the treated area. A surgeon should note your pupil size, "but there is only a rough correlation between pupil size and glare,'' says Dr. Robert Maloney, director of the Maloney Vision Institute in Los Angeles and a refractive surgery specialist.
Back to Procedure Main