The thermomechanical history of the melt under injection compression molding follows a quadrilateral-shaped path, rather than conventional triangular-shaped path, over the P-v-T diagram. The control capacity and flexibility over post-filling is significantly enhanced. It thus can produce parts with better dimensional control with less frozen-in orientation than those from conventional injection molding. This paper is devoted to study its technological application on the precision molding of parts with precision contours. A modified injection molding machine incorporating compression mechanism, and a mold with movable wall and shut-off mechanism, are used. The quality of injection-compression-molded polysytrene convex lenses is defined and compared with those injection molded. With the same cooling time, injection compression can produce lenses with better quality than those without compression.