Custom Eyes by Elvira Maricic For those looking for the most perfect vision possible, a good thing may soon get even better print article      send to a friend

LASIK, which stands for laser assisted in situ keratomileusis, is a surgical vision correction technique that utilizes the excimer laser. In the procedure, which only takes a few minutes, an instrument called a microkeratome creates a corneal flap, which acts as a hinge. The flap is folded back and the laser reshapes the cornea below the flap. If the patient is nearsighted, tissue closer to the central part of the cornea is removed to decrease its curvature or flatten it. If a patient is farsighted, tissue in the peripheral part of the cornea is removed to increase its curvature. The flap is then closed, adhering naturally and requiring no stitches. After surgery, 95 percent of patients achieve 20/40 vision or better.

Soon, with wavefront-guided custom LASIK, also referred to as "custom ablation," physicians will be able to perform customized laser vision correction based on wavefront measurements, potentially increasing the chance that patients will see 20/20 or better after undergoing LASIK.

According to Joseph M. Thomas, MD, the purpose of wavefront-guided custom LASIK is to improve vision beyond the range that it can be improved now. "It's just a more sophisticated way of measuring the eye and ultimately applying laser correction to those measurements," says Dr. Thomas, the director of refractive surgery at University Hospitals in Cleveland.

Figuring it Out

While the idea of using this technology to achieve perfect vision is exciting, just what, exactly, is it?

"Light travels in flat sheets called wavefronts, and the irregularities or aberrations in the cornea and the lens of the eye wrinkle the light waves and create wavefront errors or distortions. That's what this whole topic is about," says Dr. Thomas.

"The history of wavefront technology dates back to the mid-1970s. It came out of the University of Heidelberg in Germany and was originally developed for astronomical applications for measuring wavefront distortions from light traveling through the atmosphere and entering a telescopic lens.

"Measuring these distortions enabled the researchers to re-form the imperfect wavefront created by the atmospheric conditions into their ideal condition. They used flexible membrane mirrors to do this."  The result was that they were able to see things in the atmosphere much more clearly.

According to Dr. Thomas, wavefront technology measures aberrations in the eye unaccounted for by the more common types of measurements that physicians currently take of the sphere of the eye. These distortions are detected by Hartmann-Shack sensors, which track and measure the optical path of the light rays through the eye and detect all the aberrations at all points in the optical system. "Light enters the eye and is then reflected off the back of the eye and comes back scattered through the pupil. That's when the eye produces these 'aberrated wavefronts'.  Ultimately, the information from these wavefront maps (you can think of them almost as a fingerprint of the eye) is gathered, and these higher-order aberrations are corrected with the excimer laser," Dr. Thomas explains. The VISX, Alcon Summit/Autonomous and Bausch and Lomb wavefront sensors all use the Hartmann-Shack method.

"Ultimately, [surgeons] feel that they might be able to improve the ability of someone to see consistently greater than 20/20 vision--20/16 vision, 20/10 vision," he adds.

Not Without Risk

In addition to improved vision, this new approach to refractive surgery may also decrease the chance that patients will lose best-corrected visual acuity or experience postoperative night glare. Still, laser vision correction is surgery, and like any surgery, it involves risk. While most problems and complications can be managed, they do occur in 1 to 2 percent of patients.  These complications can include under and over correction, astigmatism, infection, night vision difficulties, delayed healing, and corneal haze.

It is also important to select the right surgeon.  However, before you pick up the phone to make an appointment with your refractive surgeon, note that this procedure is still in the developmental phase. "There are some trials going on right now, but it's going to be quite some time before it's FDA approved and available to the general public. There is a lot of information that needs to be deciphered before they can actually apply this consistently to patients," says Dr. Thomas. 

Since this newest procedure will not be available for a while, that just gives you plenty of time to do your pre-surgical homework.  Patients who are interested in improving their vision through laser surgery can also take advantage of the laser vision correction procedures that are currently available. If you are one of these potential patients, the best place for you to start is by discussing the options with your ophthalmologist.