Method for making silicone hydrogel contact lenses

A method for making a contact lens, comprising the steps of:

• (1) obtaining a fluid polymerizable composition, wherein the composition comprises a solvent mixture and a polymerizable material including at least one silicone-containing prepolymer dissolved therein, wherein the silicone-containing prepolymer includes hydrophilic and hydrophobic segments and two or more actinically crosslinkable groups and is capable of forming, in the absence of any monomer and/or crosslinking agent, a silicone hydrogel contact lens which has at least one property selected from the group consisting of an apparent oxygen permeability of at least 40 barrers, an Ionoflux Diffusion Coefficient D, of greater than about 1.5×10−6 mm2/min, an elastic modulus of from about 0.2 MPa to about 2.0 MPa, and a water content of from about 15% to about 80% by weight when fully hydrated, wherein the solvent mixture comprises at least one organic solvent and a small amount of water, wherein the organic solvent is capable of dissolving the polymerizable material to form a solution, and wherein the amount of the water present in the solvent mixture is from about 2% to about 15% by weight and is low enough not to induce macroscopic phase separation as characterized by that the fluid polymerizable composition is cloudy and a contact lens made from the polymerizable composition has a light transmissibility (T %) at around 500 nm of less than about 85%;
• (2) introducing the fluid composition into a cavity formed by a mold, wherein the mold has a first mold half with a first molding surface defining the anterior surface of a contact lens and a second mold half with a second molding surface defining the posterior surface of the contact lens, wherein said first and second mold halves are configured to receive each other such that a cavity is formed between said first and second molding surfaces;
• (3) actinically irradiating the fluid composition in the mold to crosslink said polymerizable material to form an in-situ contact lens being in an organic, solvent-swollen state and having an increased mechanical strength of at least 1.2 folders of the mechanic strength of a control in-situ lens prepared from a control composition free of water;
• and
• (4) opening the mold and removing the in-situ lens in the organic solvent-swollen state from the mold.