Multifocal ophthalmic lens with induced aperture

Abstract From the Canadian patent

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 repidly 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. To …