Abstract: Bifocal contact and intraocular lenses are described wherein a viewing area which has an extend generally corresponding to the maximum pupil area of the wearer, said viewing area having a central circular refractive zone having a first focal length corresponding to distance or reading vision, and a plurality of annular, concentric refractive zones which alternate between a second focal length corresponding to the other of reading and distance vision and said first focal length as they extend outwardly from said central zone, wherein the total number of said zones is at least 20. Preferably, at least one of the zones has a power which is more negative than a zone of the same character which is situated closer to the center of the lens.

Abstract: A bifocal contact lens has a viewing area divided into a plurality of near vision zones (1,3A) and distance vision zones (2,2A, 3) which are substantially concentric with respect to the optical axis (P,Q) of the lens. Each near vision zone is adjacent to a distance vision zone or to a middle distance zone and at least one of the near vision zones comprises an aspherical lenticular surface. An important advantage of the lens is that the aspherical surface can be merged into an adjacent spherical surface with less discontinuity at the junction between the adjacent zones.

Abstract: A hydrophilic terpolymer suitable for manufacture into shaped articles, said terpolymer being substantially the polymerization product of hydroxyalkyl acrylate or methacrylate, a vinyl comonomer having a high affinity for water, e.g. N-vinyl pyrrolidone, and a polymerizable, unsaturated carboxylic acid, e.g. methacrylic or acrylic acid. The terpolymer is particularly adaptable for use as a contact lens by bringing it in contact with a buffered aqueous alkaline solution thereby affording a hydrogel having a water content between about 55-85% by weight of the total.A preferred embodiment of the invention is the polymerization product of a reaction mixture comprising 30-50% by weight of vinyl pyrrolidone, up to about 3% of a crosslinking agent such as ethylene glycol di-methacrylate, methacrylic acid amounting to about 0.25--3.5% by weight, and 2-hydroxyethyl methacrylate which constitutes the balance.