a method is provided for manufacturing an optical plastic article formed of a plastic resin composition and having a homogeneous construction and a surface shape within a predetermined dimensional accuracy . a first step includes injection molding melted resin of the plastic resin composition into a mold cavity to produce a primary molding . a second step includes injection molding melted resin of the plastic resin composition which is the same as in the first step over at least a portion of the primary molding to form a secondary molding melt - welded to the primary molding and having the surface shape within the predetermined dimensional accuracy . the secondary molding has a secondary molding maximum thickness less than a limit thickness at which shrinkage exceeds limits of the predetermined dimensional accuracy . the optical plastic article has an optical plastic article thickness defined by the primary molding and the secondary molding greater than the limit thickness . the primary molding is preferably preheated prior to the secondary molding being melt - welded thereto and can have a thickness greater than the limit thickness .