Wavefront guided laser treatment and “higher order” refractive aberrations:

In addition to the patients basic refractive error, the cornea has small hills and valleys called “higher order aberrations.” These also contribute to a patient’s blurry vision. The technology is now available to measure and treat these small hills and valleys. The treatment is called “wavefront” or “custom” PRK / LASIK. It is “custom” because a person’s higher order aberrations may be as unique as their fingerprint. The potential advantages of custom over standard laser treatments are less nighttime glare, better vision in low light, and sharper vision.