A functional wafer of the present invention is disclosed to solve manufacturing difficulties involved in the production of optical elements such as polycarbonate ophthalmic lenses. The functional wafer may include a front layer, a functional layer, and a back layer, whereas the front layer and the back layer are bonded to the functional layer with or without additional adhesive. Said functional layer is smaller than at least the front layer by about 0.5 mm to 5 mm along the perimeter edge. A functional wafer of this construction can be conveniently and effectively incorporated into a lens through an insert injection molding process, in which said back layer will be in contact with the lens material.