The "best form" or "corrected curve" shape of a lens is one that provides as close to the the same vision at center and in the periphery as possible, as the eye moves normally behind the lens.
The form of a given lens is determined by "base curve selection." The base curve of a lens is the surface curve that serves as the basis or starting point from which the remaining curves will be calculated.
The maximum thickness of a lens, for a given prescription, varies with the form of a lens. Flatter lens forms are slightly thinner than steeper lens forms, and vice versa.
