PURPOSE: Harold Ridley (1906-2001) is widely known as the person who developed and implanted the first intraocular lens, but some details of this early event have been unknown or misunderstood. DESIGN: Historical review. METHODS: Historical documents were reviewed, including contemporaneous journal articles, medical presentations, and newspapers. RESULTS: In the fall of 1949, a medical student asked Ridley if he would replace the crystalline lens after performing a cataract extraction, and Ridley quickly developed an intraocular lens. It was well-known throughout World War II, and had been published in September 1948, that fragments of acrylic airplane windshields were inert when lodged in the eyes of wartime aviators. The acrylic material Ridley used, Transpex I, had been used for optical applications, such as spectacle lenses, since at least 1944. Ridley performed the first permanent intraocular lens implant secondarily on Feb. 8, 1950 in a patient who had initially had extracapsular cataract extraction in November 1949. The initial intraocular lens had the same radius of curvature as the crystalline lens, even though acrylic was known to have a higher refractive index, and, therefore, the first patient was left with a spherical equivalent postoperative refraction of -21.0 D. In the early series of lenses, Ridley sterilized the lenses with cetrimide, a chemical invented by the manufacturer of Transpex, but as the cetrimide could not always be fully rinsed off, an intense postoperative uveitis was common. CONCLUSIONS: Design and construction of the first intraocular lens by Ridley in 1949 proceeded rapidly, and early mistakes were made. Nonetheless, by 1951, Ridley had proven that good outcomes were possible, and thereby spurred the ophthalmic community to pursue further work which ultimately resulted in common use of intraocular lenses several decades later.