Many humans are ametropes (have some sort of optical aberrations leading to imperfect eye optical system). These aberrations are classified in to two categories:1. Conventional or lower end aberrations; responsible for the common refractive errors as farsightedness, nearsightedness and astigmatism.They account for 90% of the optical aberrations and are treatable by conventional methods as spectacles, contact lenses or conventional laser refractive surgeries as LASIK, LASEK...etc.2. High order aberrations; like chromatic aberrations, aberrations...