Abstract: Multifocal lenses are defined by nonconical aspheric optical surfaces. Various alternative surface shapes provide a central distance vision region surrounded by an optical step. The optical step has rapidly increasing power in the radial direction which creates an induced aperture through which the cortical elements of the vision system are induced to concentrate. The induced aperture results in increased clarity in distance vision. Nonconical aspheric optical surfaces are defined to produce the desired optical power distributions. These surface functions are also provided in form of polynomial series for simplicity of use in computer driven lathes for shaping contact lenses. The invention includes contact lenses, scleral lenses, intraocular lenses, and lenses impressed or surgically shaped within the corneal tissue as well as methods of designing and fitting these lenses.