Method for producing bifocal contact lenses

Claim 3

The method of claim 1 wherein a. the button is eccentrically mounted in a concave surface cutting means with its center of rotation offset from the geometrical center of said button and said first, concave surface is generated in its posterior surface; b. the button comprising said first, concave surface is then mounted in convex surface cutting means, wherein the center of rotation of the cutting means and the geometrical center of the button are coaxial, and the second, convex surface generated in its anterior surface; c. generating a third, convex surface on the second side of said button wherein the center of curvature of said third surface lies on the axis of rotation which passes through the center of curvature of the second, convex surface; and d. eccentrically mounting the lens blank of step c. on a third lens carrier, of a third spindle arbor, comprising a convex surface, mounting the third spindle arbor and lens blank in a vee-block fixture, pitch-block transferring said lens blank to a fourth lens carrier on a fourth spindle arbor axially aligned with the third spindle arbor on the vee-block fixture and generating the base curve.

Claim 4

The method of claim 1 wherein the lens blank of step (b) is: a. eccentrically mounted on a first lens carrier at one end of a spindle arbor said carrier comprising at the end opposite the spindle arbor a concave curved surface approximately matching the convex surface of the lens blank; b. the spindle arbor is then mounted in a vee-block mounting fixture; c. the lens blank is eccentrically pitch block-transferred from said first lens carrier to a second lens carrier mounted, in said vee-block mounting fixture, coaxially with said first lens carrier the first convex surface being optically centered with the spindle axis; and d. the third, convex surface generated.

Claim 5

The method of claim 3 wherein the radius of curvature of the concave surface of the first lens carrier is from about 0.00 to about 0.03 mm less than that of the first convex surface.

Claim 6

The method of claim 1 wherein the lens blank of step (c), thereof, is eccentrically mounted on a third lens carrier, having a convex surface the geometric centers of the first, concave surface of the lens blank and convex surface of the third lens carrier being aligned as required to place the geometric centers of the final lens and blank in proper relationship.

Claim 7

The method of claim 5, wherein the radius of curvature of the convex surface of the third lens carrier is from 0.00 to about 0.03 mm greater than the radius of curvature of the first, concave surface.

Claim 8

The method of claim 5 wherein the lens blank of step (c), of claim 1, is eccentrically mounted on the concave surface of a third lens carrier, the lens carrier and lens blank are mounted in a vee-block mounting fixture, the lens blank is pitch block-transferred to the fourth lens carrier mounted in said vee-block mounting fixture coaxially with the third lens carrier, the lens blank and fourth lens carrier are mounted in concave surface cutting means and the base curve generated.

Claim 9

The method of claim 1 wherein the posterior optical zone of the finished lens is decentered by eccentrically mounting the lens blank in edge cutting means, through use of a vee-block fixture, and generating the peripheral curves of the final lens.

Claim 10

The method of claim 1 for producing a plastic bifocal contact lens blank, for use in the preparation of plastic bifocal contact lenses, having a concave base curve on its posterior side, a second, convex and a third, convex surface on its anterior side and a circumferential edge from a button having first, posterior and second, anterior surfaces, a circumferential edge wall, a geometric center at the intersection of horizontal and vertical axes parallel to the planes of the anterior and posterior surfaces, said method consisting of, in combination, the steps of: a. eccentrically mounting a lens blank in a concave surface cutting means with its center of rotation offset from the optical center of said lens blank and generating a first, concave surface on a first side of a lens blank, wherein the center of curvature of said first surface lies on an axis offset from the optical center axis of said lens blank by a prism offset distance; b. mounting the lens blank of step a. in convex surface cutting means, wherein the center of rotation of the cutting means and the optical center of the lens blank are coaxial and generating a second, convex surface on the second side of said lens blank, wherein the center of curvature of said convex surface lies on the optical center axis of the lens blank; c. eccentrically mounting the lens blank of step b. on a first lens carrier at one end of a spindle arbor said carrier comprising at the end opposite the spindle arbor a concave curved surface approximately matching the convex surface of the lens blank, mounting said spindle arbor in a vee-block fixture, eccentrically pitch-block transferring the lens blank from said first lens carrier to a second lens carrier mounted in the vee-block fixture and accurately aligned axially with the first lens carrier, mounted in said vee-block fixture, wherein the first, convex surface of the lens blank is optically centered with the second spindle axis and generating a third, convex surface in the second side of said lens blank, wherein the center of curvature of said third, convex surface lies on the axis of rotation which passes through the center of curvature of the second, convex curve; d. eccentrically mounting the lens blank of step c. on a third lens carrier, of a third spindle arbor, comprising a convex surface, mounting the third spindle arbor and lens blank in a vee-block fixture, pitch-block transferring said lens blank to a fourth lens carrier on a fourth spindle arbor axially aligned with the third spindle arbor on the vee-block fixture and generating the base curve.

Claim 11

The method of claim 1 wherein lens blank is composed of rigid materials.

Claim 12

The method of claim 10 wherein said rigid materials comprise at least one polymer selected from the group consisting of polymers and copolymers of methyl methacrylate, cellulose esters.

Claim 13

The method of claim 11 wherein said copolymers of methyl methacrylate are selected from the group consisting of silicone-methyl methacrylate copolymers and copolymers of methyl methacrylate with fluorinated monomers.

Claim 14

The method of claim 1 wherein the lens blank is composed of a hydrophilic xerogel comprising at least one water insoluble hydrophilic polymer.

Claim 15

The method of claim 13 wherein said hydrophilic water insoluble polymer is selected from the group consisting of polymers and copolymers of hydroxylalkyl methacrylates and acrylates, N-vinyl lactams, acrylamides and the like.

Claim 16

The method of claim 14 wherein said hydrophilic water insoluble polymer is selected from the group consisting of polymers and copolymers of hydroxyethyl and hydroxypropyl methacrylates and acrylates.

Claim 17

The method of claim 14 wherein said hydrophilic water insoluble polymer is selected from the group consisting of polymers and copolymers of N-vinyl-2-pyrrolidone.

Claim 18

The method of claim 14 wherein said water insoluble hydrophilic polymer is selected from the group consisting of polymers and copolymers of acrylamide.