Provided is a method of preparing a transparent, non-elastomeric optical article including (1) combining to form a reaction mixture free of urethanation catalysts (a) a polyisocyanate component; and (b) an active hydrogen component of polyol and/or polythiol, and at least one compound containing both amine and hydroxyl functional groups; (2) allowing the polyisocyanate component to react with amine functional groups in the active hydrogen component to form an intermediate product including a polyurea prepolymer having hydroxyl functional groups in admixture with the polyol and/or polythiol and, optionally, the compound containing both amine and hydroxyl functional groups; (3) mixing the intermediate product with additional polyisocyanates and optionally a urethanation catalyst to form a second reaction mixture; (4) introducing the second reaction mixture to a mold to form a thermoset polymerizate; and (5) releasing the polymerizate from the mold. Optical films and articles prepared by the method also are provided.