
Prior to the advent of wavefront-guided LASIK, the only parameters that could be modified in order to obtain optical correction for a given patient's refractive error were the sphere, cylinder and axis. This approach, however, would often not yield the ideal optical correction and, in many cases, the post-refractive surgery patient may be able to read the 20/20 line but not clearly. In some cases, best corrected visual acuity (BCVA) would even decrease following surgery. This situation can usually be attributed to the persistence of significant amounts of higher order aberrations (HOAs).













