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How LASIK Takes Corrective Eye Surgery to New, Sharper Level

November 02, 1998|JONATHAN BOR | BALTIMORE SUN

In the 1970s, Americans blanched at the first reports of a Russian doctor who was curing nearsightedness by cutting tiny slits in the cornea. Now, more than 7,000 Americans each week are tossing their glasses after having their eyes sculpted with lasers.

The boom in refractive surgery has become so intense that ophthalmologists talk with some satisfaction about "the number of eyes" they have corrected each week, month or year.

"I do about 100 eyes in a week," said Dr. Anthony Kameen, refractive surgeon at the Greater Baltimore Medical Center. "In July, I did close to 500 eyes. We're expecting that to double in the next year."

Surgical techniques are safer and more precise than ever, thanks to innovations that are proceeding at a dizzying clip.

Through it all, the goal has not changed--to bring sharper focus by changing the shape of the eye.

People are nearsighted when their eyes are too long from front to back.

The Russian surgeon S.N. Fyodorov addressed this with a method called radial keratotomy, in which he made a series of cuts in the cornea--the clear, thin tissue that forms a protective layer over the eye. The cuts radiated out from the center of the cornea like spokes on a wheel. As they healed, the cornea contracted and the person's ability to see long distances improved.

Severe corrections called for longer slits--and more of them. Milder corrections called for shorter cuts, and fewer.

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Radial keratotomy hit its peak in the mid-1990s, when nearly 300,000 eyes in the United States were being "done" each year. But the technique had limits. First, it could take three months for the eyes to feel comfortable and for vision to stabilize. Second, surgeons had a hard time controlling the degree to which the eye contracted--making the "fix" a disturbingly inexact one.

Luckily, the rapid development of laser procedures guaranteed to make radial keratotomy a historical curiosity.

"In 1994 and 1995, RK really fell off the table, and now only about 10,000 of them are being done a year," said Irving Arons, a Massachusetts consultant who has worked with the laser industry.

In the first laser technique, called photorefractive keratectomy, or PRK, surgeons use a laser to vaporize cells on the cornea's surface.

In a more advanced technique, called LASIK (for laser-assisted in-situkeratomileusis), surgeons peel back the outer layer of the cornea, vaporize underlying cells, and then restore the flap to its original position.

LASIK is, to say the least, a marvel of technology.

The patient, calmed with a tranquilizer, lies on a table beneath a thick, metal arm that holds the laser and scope. The surgeon applies anesthetic drops to the surface of the eye, then holds the eyelid open with a ring called a speculum. Next, the surgeon places a second ring against the eye and applies suction through its center. This draws the eyeball outward and immobilizes it.

Now, a tiny slicing device called a microkeratome is used to cut the flap. Working like a tiny meat slicer placed on its side, it rides across a track on the suction ring.

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"An automated gear system drives it across," said Dr. Terrence P. O'Brien, a refractive surgeon with the Johns Hopkins Wilmer Eye Institute. "It cuts very smooth--not like shaving by hand."

Before each procedure, the machine is told how much tissue to cut--and where--by means of a plastic card that, in effect, contains the patient's prescription.

The laser clicks away for 20 to 30 seconds in most cases--as long as two minutes in the most severe cases.

"If the patient decides to move, or sneezes, I lift my foot off the petal and we stop and refocus," Kameen said.

Once the sculpting is done, the surgeon restores the flap and smooths it with a tiny rod. The operation is done--lasting no more than 10 minutes.

"With LASIK, people we do today are back to work tomorrow," Kameen said. The recovery is generally pain-free, though patients can experience dryness for a week or two.

Said O'Brien: "LASIK allows you to treat with less chance of developing scarring and halos"--rings that can form around bright lights at night. "And with LASIK, vision returns a bit quicker because the surface of the eye is kept intact, whereas with PRK an abrasion is created on the surface, which needs time to heal."

Finally, LASIK can correct severe cases of nearsightedness--as much as minus-15 diopters, a measurement that translates into 20/1000 vision or worse. In contrast, PRK reaches its limit at about minus-12 diopters.

Studies have found that the two methods are equally effective.

About 98 percent of all patients will be able to "function independently" without glasses after laser surgery, O'Brien estimated. Most of the remaining patients might need glasses to correct a small degree of nearsightedness that remains, which can usually be corrected with a second procedure.

A small percentage of patients--"probably less than 0.5 percent," he said--will actually lose vision.

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The savvy consumer should make sure that the surgeon has done plenty of procedures and is a corneal specialist whose experience extends beyond refractive surgery, O'Brien said.

And, yes, laser surgery is expensive. It can run more than $5,000 for both eyes. Don't count on insurance covering it, either. Insurers consider this elective surgery a convenience rather than a medical necessity.

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