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Stanford Report, August 6, 2003

Clinic offers heightened standard in laser vision correction


Stanford Eye Laser Center is now offering a new customized laser vision correction system to patients who are nearsighted. The treatment, called wavefront-guided LASIK, is viewed as superior to conventional LASIK eye surgery. It’s designed to measure and correct unique imperfections in each individual’s vision, and these “custom” measurements allow most patients to see 20/20 or better without contact lenses or glasses.

Edward Manche, MD, associate professor of ophthalmology and director of cornea and refractive surgery, was one of the first physicians in the country to perform this treatment following approval by the U.S. Food and Drug Administration.

Edward Manche measures the unique imperfections in the eye before a computer constructs a one-of-a-kind, customized treatment plan that is specifically tailored for each patient. Photo: Neale Mulligan

“It’s a fundamental change in the way we do LASIK surgery,” said Manche. “We are able to carefully measure the unique imperfections of each individual’s vision and develop a treatment plan.”

Manche is using a wavefront-guided system made by VISX Inc. The FDA is currently reviewing data submitted by Bausch & Lomb and as soon as the company receives agency approval, Stanford Eye Laser Center plans to use both systems, which will make it the first center in the country to offer two options. “Each system has its own unique features,” said Manche. “We want to have the ability to choose from two distinct technologies to select the best treatment for each patient.”

All eyes have some degree of imperfections. One way to measure the focusing errors of an eye is to measure its wavefront. Patients look into a light and the wavefront device uses a camera sensor to measure light rays as they reflect out of the eye. This generates a virtual map showing the precise locations and extent of one’s visual aberrations.

The wavefront of a perfect eye has a flat surface because light rays travel uniformly through the eye. In an imperfect eye, the wavefront map is wavy because some light rays reach the retina before others, while others hit the retina at different locations. Conventional LASIK is based on a patient’s eyeglass prescription and does not include the measurements of the eye that wavefront technology provides, Manche said.

In a classic example of “look before you leap,” patients are now able to preview their potential vision before staring down an excimer laser. Once the preoperative measurements are taken, surgeons have the option to create a unique trial lens that incorporates the patient’s correction. This lens is then fitted into a trial frame so the patient can preview their new and improved vision.

Just like conventional LASIK (laser-assisted in situ keratomileusis), the wavefront procedure lasts about 10 minutes. A precision instrument called a microkeratome is used to cut a microscopically thin, hinged flap on the top of the cornea. The flap is carefully peeled back.

In the meantime, data from the wavefront image has been transferred into a computer that controls an excimer laser. The computer superimposes the map over the eye, allowing a surgeon to adjust the laser to compensate for aberrations. The surgeon then zaps the exposed cornea with a series of rapid pulses from the laser, removing small and precise amounts of corneal tissue. These bursts from the laser reshape the corneal tissue to correct nearsightedness as well as astigmatism. Excimer laser light does not penetrate into the eye leaving other structures such as the iris, lens, and retina unscathed. The flap is replaced and the eye’s natural suction enables it to heal without stitches.

In a recent study of nearly 190 participants who had undergone the wavefront procedure a year earlier, 100 percent could see well enough to legally drive a car without glasses or contacts. Ninety-eight percent of participants achieved uncorrected visual acuity of 20/20 or better, and 70 percent of those were 20/16 or better.

Wavefront-guided LASIK also may have potential to re-treat patients who have undergone previous refractive surgery but are suffering from what Manche calls “visual disturbances” such as glare, halos, distortion, ghosting of images and difficulty seeing at night.

“This is probably the most compelling reason for this technology. A very small percentage of patients have complications following conventional LASIK surgery,” said Manche.

Given the hype surrounding wavefront, Manche is worried that people’s expectations are being raised even higher. “Even though it’s been shown to be somewhat better than conventional LASIK ­ that is, better in how many people achieve best vision and in how fewer people experience side effects ­ this is not going to be a panacea.”

Wavefront LASIK will cost patients $5,500, conventional LASIK surgery about $5,000. Most health insurance plans do not cover LASIK surgery so patients pay for the procedure themselves.

Procedure fixes farsightedness with radio frequency energy (4/24/02)

Eye Laser Center tests new implantable contact lens (6/12/02)

Stanford Eye Laser Center