Abstract: Spherical hydrophilic contact lenses having a characteristic tricurve configuration designed to correct myopia (nearsightedness) are described. The center zone (A1) of the lens is substantially thinner than the periphery (A3) allowing enhanced oxygen transmission and comfortable, increased wearing times while the thicker mid-periphery (A2) imparts necessary integrity and handling characteristics for convenience in manual manipulation. Lenses are molded or cast directly in the desired tricurve configuration using specially designed replica molds made from metal master molds.

Abstract: Truncated contact lenses are produced in a direct casting operation using a mold assembly of a male mold member and a female mold member, both of which have molding surfaces and only one of which is provided with an inwardly flexible continuous rim portion. When vulcanizable or polymerizable constituents are placed in the mold, the two mold members are brought together, the flexible rim is flexed inwardly and the finished lens of the desired shape is obtained. The flexible rim is composed of a circular portion having two ends and a straight line connecting the two ends. This defines a chord and provides the finished lens with the truncation desired.Preferably the lens also has a toric surface and prism ballast to assist in positional stability of the lens on the eye of the wearer.