US Patent 7537339 Hybrid contact lens system and method of fitting

A hybrid contact lens comprises a substantially rigid zone having a base curve with a first curved section defined by an apical radius and an aspheric section defined by a conic constant. A substantially flexible hydrophilic peripheral portion is coupled to the substantially rigid zone, the peripheral portion having one of a plurality of radii, wherein a conic constant of the aspheric section varies with apical radius, so as to provide a nearly constant deviation between the aspheric shape of the aspheric section and a sphere having a radius equal to the apical radius, regardless of the length of the apical radius.