Diffractive multifocal contact lens

A method for making multifocal contact lenses, comprising the steps of:

• (1) obtaining a female lens mold half, a male insert mold half and a male lens mold half, wherein the female lens mold half has a first molding surface defining the anterior surface of a multifocal contact lens to be molded and the front convex surface of a diffractive insert to be molded, wherein the male insert mold half has a second molding surface that defines the back concave surface of the diffractive insert to be molded and comprises a circular or annular portion defining a stepped-transition diffractive surface, wherein the male lens mold half has a third molding surface defining the posterior surface of the multifocal contact lens to be molded, wherein the male insert mold half and the female lens mold half are configured to receive each other such that an insert-molding cavity is formed between the second molding surface and a central portion of the first molding surface when the female lens mold half is closed with the male insert mold half, wherein the male lens mold half and the female lens mold half are configured to receive each other such that a lens-molding cavity is formed between the first and third molding surfaces when the female lens mold half is closed with the male lens mold half;
• (2) dispensing an amount of an insert-forming composition on the central portion of the first molding surface of the female lens mold half;
• (3) placing the male insert mold half on top of the insert-forming composition in the female lens mold half and closing the male insert mold half and the female lens mold half to form a first molding assembly comprising the insert-forming composition within the insert-molding cavity;
• (4) curing the insert-forming composition in the insert-molding cavity of the first molding assembly to form the diffractive insert made of a second crosslinked polymeric material formed from the insert-forming composition and comprising the stepped-transition diffractive surface created on the back concave surface;
• (5) separating the first molding assembly obtained in step (4) into the male insert mold half and the female lens mold half with the diffractive insert that is adhered onto the central portion of the first molding surface;
• (6) dispensing a lens-forming composition in the female lens mold half in an amount sufficient for filling the lens-molding cavity;
• (7) placing the male lens mold half on top of the lens-forming composition in the female lens mold half and closing the male lens mold half and the female lens mold half to form a second molding assembly comprising the lens-forming composition and the diffractive insert immersed therein in the lens-molding cavity;
• (8) curing the lens-forming composition with the diffractive insert immersed therein in the lens-molding cavity of the second molding assembly to form a multifocal contact lens that comprise a first crosslinked polymeric material (lens bulk material) formed from the lens-forming composition and the diffractive insert embedded partially in the first crosslinked polymeric material;
• (9) separating the second molding assembly obtained in step (8) into the male lens mold half and the female lens mold half, with the multifocal contact lens adhered on a lens-adhered mold half which is one of the female and male lens mold halves;
• (10) removing the multifocal contact lens from the lens-adhered lens mold half, and
• (11) subjecting the embedded multifocal contact lens to post-molding processes including one or more processes selected from the group consisting of extraction, hydration, surface treatment, packaging, sterilization, and combinations thereof.

A method for making multifocal contact lenses, comprising the steps of:

• (1) obtaining a female insert mold half, a male lens mold half and a female lens mold half, wherein the female insert mold half has a fourth molding surface that defines the front convex surface of a diffractive insert to be molded and that comprises a circular or annular portion defining a stepped-transition diffractive surface, wherein the male lens mold half has a third molding surface defining the posterior surface of a multifocal contact lens to be molded, wherein the female lens mold half has a first molding surface defining the anterior surface of the multifocal contact lens to be molded, wherein the female insert mold half and the male lens mold half are configured to receive each other such that an insert-molding cavity is formed between the fourth molding surface and a central portion of the third molding surface when the female insert mold half is closed with the male lens mold half, wherein the female lens mold half and the male lens mold half are configured to receive each other such that a lens-molding cavity is formed between the first and third molding surfaces when the second female mold half is closed with the male mold half;
• (2) dispensing an amount of an insert-forming composition on the central portion of the first molding surface of the female lens mold half;
• (3) placing the male insert mold half on top of the insert-forming composition in the female lens mold half and closing the male insert mold half and the female lens mold half to form a first molding assembly comprising the insert-forming composition within the insert-molding cavity;
• (4) curing the insert-forming composition in the insert-molding cavity of the first molding assembly to form the diffractive insert made of a second crosslinked polymeric material formed from the insert-forming composition and comprising the stepped-transition diffractive surface created on the front convex surface;
• (5) separating the first molding assembly obtained in step (4) into the male insert mold half and the female lens mold half with the diffractive insert that is adhered onto the central portion of the first molding surface;
• (6) dispensing a lens-forming composition in the female lens mold half in an amount sufficient for filling the lens-molding cavity;
• (7) placing the male lens mold half on top of the lens-forming composition in the female lens mold half and closing the male lens mold half and the female lens mold half to form a second molding assembly comprising the lens-forming composition and the diffractive insert immersed therein in the lens-molding cavity;
• (8) curing the lens-forming composition with the diffractive insert immersed therein in the lens-molding cavity of the second molding assembly to form a multifocal contact lens that comprise a first crosslinked polymeric material (lens bulk material) formed from the lens-forming composition and the diffractive insert embedded partially in the first crosslinked polymeric material;
• (9) separating the second molding assembly obtained in step (8) into the male lens mold half and the female lens mold half, with the multifocal contact lens adhered on a lens-adhered mold half which is one of the female and male lens mold halves;
• (10) removing the multifocal contact lens from the lens-adhered lens mold half;
• and
• (11) subjecting the multifocal contact lens to post-molding processes including one or more processes selected from the group consisting of extraction, hydration, surface treatment, packaging, sterilization, and combinations thereof.