Organic polymer lens mold

A mold for an organic polymer, ophthalmic lens element comprising separate upper and lower mold members, each mold member being composed of a thermoplastic polymer, the lower mold member comprising a bottom portion having a surface contour that corresponds to, but is the reverse of, a surface contour on the lens element being molded, and an annular wall rising vertically from an outer edge of the surface contour of the bottom portion and defines the periphery of a central, bowl-shaped cavity with contours that conform to those of an ophthalmic lens to be molded therein, and an annular rim extending radially and outwardly from an upper end portion of the vertical annular wall, the upper mold member having a central portion with an under surface that corresponds in contour to that of the upper surface of the ophthalmic lens to be molded, and with an annular rim that surrounds the central portion and that rests on the annular rim of the lower member when the two members are assembled, the mold having means for locking the upper mold member tightly against the lower mold member when the mold members are assembled, the locking means being a plurality of flat tabs that project from the annular rim on the upper mold member at spaced intervals, and that cooperate with L-shaped cutouts in a wall upstanding from the outer edge of the annular rim portion on the lower mold member within which the upper mold member rests when assembled.