Leonhard Euler (1707-1783). Caricature of the Swiss mathematician and physicist Leonhard Euler. Euler made discoveries in a wide range of fields, including geometry, infinitesimal calculus, trigonometry, algebra, number theory, continuum physics, lunar theory, and graph theory, to name a few. His eyesight grew worse over his career, and by 1735 he was nearly blind in his right eye. He believed his cartography work for the St. Petersburg Academy caused this blindness.