US Patent 8042940 Opthalmic lenses having reduced base out prism

The invention generally relates to a lens and the method of manufacturing progressive addition lenses (PAL) to remove unwanted base out prism and minimize excessive convergence, comprising determining basic configuration of two major lens surfaces to provide a distance portion and near portion, wherein diopter power increases from the distance portion of the lens to the near portion; selecting an amount of prism reduction; and reducing base out prism that inherently occurs as diopter power increases by altering the configuration of the lens as a function of the amount of prism reduction to minimize any disruption of optical properties a lens while decreasing base out prism.