Abstract: An aspheric multifocal contact lens for wearing by a patient with presbyopia is disclosed. The lens has a lens body with a rear surface adapted to fit on the surface of the eye and a front surface that interacts with the rear surface to bring about the desired optics of the lens. The lens also has a centrally located and generally circular first optic zone providing a first power correction for near vision, and a second optic zone concentric with the first optic zone and located peripherally therefrom providing a second power correction for distance vision. A transition zone concentric with the first optic zone is located between said first and second optic zones. The transition zone provides a rapid power shift of about 0.8 to about 1.6 diopters over a distance of about 0.25 mm between the power correction of the first and second zones.

Abstract: A method for constructing a soft contact lens having a prescribed power correction for focusing light on the retina of an eye is described. The method provides a soft contact lens that, when in place ("flexed") on the wearer's eye, is designed and manufactured to provide a substantially ellipsoidal anterior surface. In the method, an eye model including a cornea, a crystalline lens and a retina is constructed. Then a shape for an anterior surface of the cornea is selected to be a conic section having an eccentricity in the range of about 0.14<e<0.63. Next, a preliminary soft contact lens is selected having a center thickness, a radius, a posterior contact lens surface and an anterior contact lens surface to provide a prescribed plus or minus correction power such that, when applied to the anterior surface of the cornea, the anterior contact lens surface defining a conic section having a shape factor in the range of 0<E<1 or -1<E<0.