Preparing a hydrated contact lens

A method for preparing a hydrated corrective contact lens or a shaped eye bandage which contains from about 45% to about 65% water comprising:

• A. lining an open-ended mold with a polyester film material and closing one end of the mold with a cap plug;
• B. placing a homogenous blend of from about 67.2% to about 79.3% of HEMA;
• from about 14.25% to about 35% PVP;
• from about 0.1% to about 4.04% EDMA;
• from about 0.1% to about 2.5% MA;
• from about 0.1% to 5.0% water, from about 0 to 4 ppm, based on the weight of HEMA monomer, of HQ inhibitor;
• from about 50 to 250 ppm, based on the weight of HEMA monomer, of MEHQ inhibitor and from 0.005% to about 0.2% of a low temperature free radical polymerization initiator operable between the temperatures of from about 23.degree. C. to about 80.degree. C., into the polyester-lined mold of (A);
• C. de-gassing the homogeneous blend of (B) while in the mold to remove substantially all oxygen present;
• D. closing the mold of (C) with a cap plug to prevent contamination with atmospheric oxygen;
• E. subjecting the homogeneous blend of (D) to a three stage polymerization process wherein the initial polymerization reaction is conducted at a temperature of from about 23.degree. C to about 30.degree. C for from about 16 hours to about 36 hours in a medium capable of continuously absorbing the heat of the reaction to control the reaction exotherm;
• F. removing the mold from the heat absorbing medium of (E) and conducting a second-stage polymerization reaction by heating the mold to a temperature of from about 40.degree. C to about 80.degree. C in the absence of any additional polymerization initiator, for from about two hours to about six hours to form a solid, self-supporting, partially polymerized rod;
• G. removing the cap plugs from the mold of (F) and gently forcing the solid rod, encased in the polyester film, from the mold;
• H. conducting the third-stage polymerization reaction by heating the solid rod of (G) encased in the polyester film, to a temperature of from 110.degree. C to 115.degree. C for from about 24 hours to about 36 hours to substantially complete polymerization of the rod;
• I. removing the polyester film casing from the polymerized rod of (H);
• and subjecting the rod to cutting, machining and polishing to form a corrective contact lens or a shaped eye bandage;
• and
• J. hydrating the contact lens or shaped eye bandage of (I) in a saline solution buffered to maintain a pH of from about 7.0 to about 7.1 until from about 45% to about 65% water has been absorbed.