The surgeon first uses a suction ring to flatten the eye in order to cut a flap in the cornea, folding back the flap back to reveal the middle section, called the stroma. Then the surgeon uses pulses from a computer-controlled laser to destroy a portion of the stroma, and replaces the flap.
The entire procedure, which costs $4,176 on average, is usually over in less than 15 minutes. It is not covered by most health insurance policies because it is considered a cosmetic or elective procedure.
Dr. Cynthia MacKay, one of the few ophthalmologists who has spoken out against the procedure, said the surgery can injure the eye because it severs tiny corneal nerves, thins the cornea and makes it weaker, and permanently alters the shape of the eye.
She said after Lasik, all people lose contrast sensitivity, the ability to distinguish between shades of gray, to some degree. It is an elective procedure, she emphasized, that does not provide any benefits that cannot be obtained with glasses or contact lenses.
“There is nothing wrong with eyes that undergo Lasik except for the fact that they need glasses for distance,” Dr. MacKay said. “They see well before the procedure and ought to see equally well after the procedure. But they don’t.”
Indeed, the F.D.A.’s new clinical trial, carried out with the National Eye Institute and the Navy Refractive Surgery Center and published last year, was the first to report that people who did not have dry eyes or visual aberrations before Lasik were at high risk for developing these problems: 28 percent of these participants developed dry eyes after surgery, and 45 percent reported a new visual aberration three months after surgery.
But many of the trial’s 574 participants reported having visual aberrations and dry eyes before surgery, and the study concluded that Lasik slightly reduced the prevalence of these problems.