Harold Ridley pioneered the use of Perspex lenses in the treatment of cataract. He was born on 10 July 1906 in Kibworth, Leicestershire. His father, Nicholas Charles Ridley FRCS, was a former Naval surgeon who became an ophthalmic surgeon at Leicester Royal Infirmary. His mother, Margaret Parker - heiress of a family which had made its fortune by the invention of the safety pin - had been a friend of Florence Nightingale, on whose knee Harold remembered sitting as a small boy. He was educated at Charterhouse and Pembroke College, Cambridge, from which he went on to St Thomas's for his clinical training. After junior posts with Cyril Nitch and Philip Mitchiner, he specialised in ophthalmology and trained at Moorfields under A C Hudson, P G Doyne and Affleck Greeves. He was appointed to the consultant staff of Moorfields in 1938. Joining the RAMC at the outbreak of war, he was posted to Ghana, where he seized the opportunity to make a study of onchocerciasis, on which his monograph was a major contribution. During the war he had the opportunity of treating injured airmen and noticed that slivers of Perspex from the cockpit canopy embedded in the eye were light and inert, and were rarely rejected as foreign bodies. One day a student, who had never previously seen a cataract removed, remarked that it was a pity that the lens could not be replaced with a clear one. Working at first in great secrecy with John Pike, an optical scientist from Rayner Lenses, and using the same Perspex used in the Hawker Hurricane fighters, Harold performed the world's first intra-ocular lens transplant on a 45-year-old woman on 29 November 1949. When the secret broke, Harold Ridley was subjected to almost universal condemnation by his peers, who regarded the procedure as reckless, but events were to prove him right. He continued to work at Moorfields and, after retirement in 1971, continued to serve the World Health Organisation and the Royal Commonwealth Society for the Blind. He was a popular teacher, though a speech impediment sometimes made his lectures hard to follow, and so he always took the trouble to have notes made and handed out. He took immense trouble to help and encourage students, especially those who were enthusiastic, had enquiring minds and could share his impish sense of humour. A dining club of his former trainees met annually in his memory, and a Ridley Foundation was set up to help young ophthalmologists. A recipient of innumerable honorary degrees, he was Vice-President of the Ophthalmological Society of the United Kingdom, and was elected to the Royal Society in 1986. He was awarded the Galen medal of the Worshipful Society of Apothecaries in 1986, the Lord Crook gold medal of the Spectacle Makers' Company in 1987, the Gullstrand medal of the Swedish Medical Society in 1992 and the Gonin medal of the International Council of Ophthalmology in 1994. He was knighted in 2000. He underwent his own cataract operation twice. He married Elisabeth Jane Wetherill in 1941, and had two sons and a daughter, none of whom went into medicine. He was a keen fly-fisherman. He died on 25 May 2001.