This valediction to the late Sir Harold Ridley commemorates the 50th year of his first publication in the St Thomas's Hospital Report, describing his pioneer undertaking to research, design, and implant an intraocular lens to correct aphakia.

Dissatisfied with the poor acuity and loss of binocular single vision following unilateral cataract extraction and the poor outcome, particularly in children, with the contact lenses then available, he had early in his career envisaged using an artificial lenticulus. His research was catalysed by the now famous remark of a medical student, that it was a pity that the cataract he had seen extracted could not be replaced by a clear lens. In his paper Ridley described his threefold problem. Firstly, he had to find an inert material for what would be an intraocular foreign body. In this he was inspired in his choice of poly(methylmethacrylate) which became the gold standard of implant materials. Animal experiments were rejected by Ridley, although they might have added to the surgical techniques proposed, on the grounds of adding little to the known intraocular tolerance of the material. This lack of inflammatory response to glass and plastic intraocular foreign bodies, provided they did not touch the iris, had been observed in the eyes of injured aircrew who survived aerial combat …