A method for producing a semi-finished product for a plus or minus power lens having a toroidal or atoroidal back that is configured as a prescription surface. According to the method, a blank having a diameter DR and a front having a radius of curvature rV is fixed on its front for the purpose of machining the back and is subjected to cutting, the prescription surface being produced only across a part of the diameter D. Deviating from the curvature of the prescription surface a dimension is left, thereby producing an additional surface, either in the areas of the back in which the generation of the base radius rB would result in the thickness hB of the edge being smaller than the minimum dimension hmin, so that the thickness of the semi-finished product is not smaller than the minimum dimension hmin at any point, and the maximum thickness hB of the edge being five times as large as the thinnest point S of the semi-finished product, or in the areas of the back where the generation of the cylinder radius rZ would result in the edge being thicker than a thickness hB of the edge of the semi-finished product in a plane EB of the base radius rB, the thickness is reduced so that the thickness of the semi-finished product so produced does not exceed the maximum dimension hB at any point.