The website Progressive Memories was created at the end of 2010.The goal was to write the history of the evolution of the ophthalmic industry between the 1960's and the 1990's, this fascinating period where the power balance on the worldwide market changed fundamentally.The evolution of the progressive power lens (PPL) market and the shares of the big manufacturers in this market was key for the change. The chronicle is particularly dedicated to all people, who were fueling the market expansion of this new and most sophisticated spectacle lens by their creativity and professionalism.This first part depicts the competitive situation between the market leaders and their strategies to increase their market share.
Now, more than 3 years later, the story shall focus on the scientific and technical work achieved during these years. Calculus is a new chapter, which tries to illustrate the progress in physiological ophthalmic research and computing technology, which prepared the way from the first Varilux to the sophisticated designs of the end of the 1990's. 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. Some mathematical examples demonstrate the historical development of progressive lens design calculation.