Highly accurate laser tested in popular eye operation

Stanford Report, April 7, 2004

Highly accurate laser tested in popular eye operation
Clinical trial has eye on precise tool for improving LASIK

By MICHELLE L. BRANDT

Each year more than 1 million Americans bid adieu to nearsightedness by undergoing popular LASIK surgery. Now School of Medicine researchers are investigating whether a new laser device can lead to even more favorable results than the one used in traditional LASIK.

“If the new device is shown to have better outcomes for patients, it could become the standard of care,” said Edward Manche, MD, associate professor of ophthalmology, who is leading the study.

Two steps are involved in the LASIK procedure, during which the cornea is permanently reshaped. First, surgeons prepare the eye by creating a flap in the cornea that can be folded back during the procedure. Then they use an excimer laser to correct the shape of the cornea, thereby eliminating a patient’s nearsightedness.

A mechanical microkeratome -- a device with a precision blade that resembles a mini pizza-cutter -- is traditionally used to create the flap prior to the laser portion of the procedure. A downside of the device, Manche said, is that it can be difficult to achieve a consistent flap thickness in each eye. The flap in one eye might be thinner than in the other, for example, and some surgeons worry this could alter the outcome of the procedure for some patients.

In 1999 the Food and Drug Administration approved the use of a femtosecond laser to create the corneal flap. Pulses from the laser, which move at the rate of one-quadrillionth of a second, result in a precise cut of the cornea. A study in a 2003 issue of the Journal of Refractive Surgery showed the method resulted in greater accuracy and fewer complications when compared to cuts made by microkeratomes.

“One of the proven benefits of the laser device is its ability to more accurately create flaps of a desired thickness,” said Manche, who also directs cornea and refractive surgery at the Stanford Eye Laser Center. “If we are trying to create a 120-micron flap, for example, we usually get within 10 microns with the laser device. With the mechanical device we tend to be somewhat less accurate.”

Despite the laser’s ability to better predict flap thickness, preliminary data have shown little difference in outcomes between the laser and the microkeratome. Manche said he launched the study in an effort to answer definitively whether the laser device can improve outcomes for patients. “We define better results as a greater number of patients seeing 20/20 or 20/15 after the surgery,” he said.

During the study, 50 LASIK patients will have the all-laser procedure in one eye and the traditional procedure with the mechanical device in the other. Manche will then determine vision and subtle corneal distortions in each eye.

Manche is currently enrolling patients for the study. Study participants must be 21 or older and have moderate to extreme nearsightedness. They cannot be pregnant or nursing, and they cannot have eye disease or have had previous surgeries. Participants will be charged 70 percent of the normal cost of the LASIK procedure.

Intralase Corp. manufacturers the machine used to perform the all-laser LASIK procedure. To determine if you are a candidate for this procedure, contact the Eye Laser Center at (650) 498-7020, or visit http://www.med.stanford.edu/school/eye/laser/index.html.

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