A patient from Thousand Oaks asked me about the difference between two types of LASIK technologies: wavefront-optimized and topography-guided LASIK. The terms can get quite confusing. There are three general approaches to giving the laser information about how to go about its job of sculpting a new shape into the cornea to improve vision without glasses or contacts: conventional LASIK, customized wavefront LASIK, and topography-guided LASIK. They differ in how measurements are taken of the eye and, in turn, these measurements are used to program the laser beam. Conventional LASIK is based completely on the refraction — the “which is better one or two” test (just as glasses or contact lenses are also based on the refraction). Customized wavefront LASIK is based on measurements taken by an infra-red laser beam which is shined into the eye (a different laser than the laser used to later reshape the cornea). The infra-red laser is reflected off the back of the eye and as it returns, it creates a wave of light which is distorted by the unique errors in each individual patient’s eye. When the wave of light leaves the eye, the three dimensional net distortion in that wave is mapped and called the “optical fingerprint.”  The optical fingerprint — which is unique to that individual eye — is downloaded into the laser and treated on the cornea during LASIK. The refraction is not used at all — only the optical fingerprint–  so the surgery is completely customized to that patient’s eye. Topography-guided LASIK is based on a combination of a mapping of the surface of the cornea (the “topography” of the cornea) and conventional measurements using the refraction. In high performance jobs in the military (such as US Air Force pilots), only customized wavefront technology is allowed. Topography-guided LASIK is quite new and is a promising technology whose main benefit could be in cases with primarily topographical problems on the surface of the cornea. In the United States today, however, many cases are still done using conventional surgery, particularly a form of conventional surgery called “wavefront-optimized” LASIK (which should not be confused with true customized wavefront LASIK). Wavefront-optimized LASIK is still based on the refraction like other forms of conventional LASIK, but it also incorporates non-custom changes to the edges of the treatment to improve optical quality over earlier versions of conventional LASIK. In this way, both wavefront-optimized and topography-guided LASIK use conventional, refraction-based measurements, but each modifies them differently: wavefront-optimized by employing a one-size-fits-all modification to the edges of the treatment and topography-guided by adding a customized fit based on the patients unique topography map of the surface of the cornea. “Wavefront-optimized” (WFO) is a term that was coined by Allegretto, a laser manufacturer (which is in turn owned by Alcon Laboratories). Allegretto also makes a topography-guided vision correction laser technology called “Contoura LASIK” or Topography-Guided Custom Ablation (TCAT) which was recently approved by the FDA. Another laser manufacturer, NIDEK, also makes a similar topography-guided laser technology called “CATz” (Custom Aspheric Treatment Zone).

A recent study compared visual outcomes between wavefront-optimized LASIK and topography-guided LASIK, both using technology from the same manufacturer, Allegretto. In this study, 60 eyes of 30 patients underwent LASIK for nearsightedness (myopia). Wavefront-optimized LASIK was performed in one eye and topography-guided LASIK was performed in the other eye of each patient. Results were nearly identical even though the topography-guided eyes were more customized to the patient’s cornea. However, the topography guided eyes had slightly better outcomes with a very small difference in accuracy as measured by lower order aberrations and a trend toward marginally better optical quality as measured in higher order aberrations that was not statistically significant. Again, neither of these approaches was true customized wavefront LASIK. The authors of the study concluded that wavefront-optimized and topography-guided LASIK “provided essentially equivalent outcomes after myopic LASIK.”