The second part Calculus is introduced by Bernard Maitenaz, the creator of the modern and first commercial progressive lens. Calculus describes the progress in physiological and ophthalmic optics research and in computing technology, which prepared the way from the first Varilux to the sophisticated designs of the end of the 1990s. The guideline for this research are the patents filed during this period, which document the ingenuity of the research scientists and the engineers as well as the extensive investments made for the development of progressive aspherical surfaces.