Wavefront adds an automatic measurement of more subtle distortions (called higher order aberrations) than just nearsightedness, farsightedness, and astigmatism corrected by conventional LASIK. However, these “higher order aberrations” account for only a small amount (probably no more than 10%) of the total refractive error of the average person’s eye. Conventional LASIK increases higher order aberrations. Although wavefront-guided treatments attempt to eliminate higher order aberrations, results from the clinical studies have shown that the average aberrations still increase, but less than they do after conventional LASIK. In a few studies comparing wavefront-guided LASIK to conventional LASIK, a slightly larger percentage of subjects treated with wavefront LASIK achieved 20/20 vision without glasses or contact lenses compared to subjects treated with conventional LASIK.