Ida Mann was born in 1893 in West Hampstead, London, and educated at Wycombe House School, Hampstead. Having passed the Civil Service Girl Clerks' exam, she secured a job at the Post Office Savings Bank, aged seventeen. A benevolent visit to the London Hospital in Whitechapel revived a fierce desire to study medicine and she was amazed to discover that such a career was possible if she enrolled at the only medical school open to women, the London School of Medicine for Women. Despite opposition from her father, she passed the London matriculation exam in 1914, one of only eight women out of hundreds of passes. She completed her studies, 'with no trouble and intense delight' (Mann 1986: 64), and qualified in 1920. After applying for many junior posts, she was appointed to work under the Ophthalmic House Surgeonship at the hospital. Although she had no particular interest in eyes, she soon realised that this fascinating subject was to be her life's work. She developed her specialism in ophthalmology and embryology and at the same time acquired her qualification in general surgery, becoming F.C.R.S. in 1924. She was appointed to a staff post at Moorfields in 1927 (an unpaid but prestigious position) and was the first woman to achieve this seniority. She funded her independence by establishing a private practice in Harley Street. Her curiosity led to research into the comparative anatomy of the invertebrate eye, working with the reptiles in London Zoo.

In 1941 she was appointed the Margaret Ogilvy Reader in Ophthalmology at Oxford University. During her tenure she oversaw the building of the Nuffield Laboratory of Ophthalmology, appointed Antoinette Pirie as Biochemist, replaced the matron with a more competent sister from Moorfields, re-started the diploma courses, inaugurated the Orthoptic School and re-instituted the Oxford Congress. She also continued her work for the war effort as the head of a research team working for the Chemical Defence Research Department, testing the effects of toxic chemicals on the eye. She collaborated with Rudolph Peters, biochemist, who had discovered British anti Lewisite, an antidote to the chemical warfare agent, Lewisite, and she also worked with Sir Howard and Lady Florey on the effects of penicillin on bacteria in humans. Her efforts were recognised by the university in 1945 when she was given a personal professorship, the first woman to receive one.

In 1944 she married Professor William Gye, a pathologist and director of the Imperial Cancer Research Fund. After the war, partly due to his poor health, they emigrated to Australia where she continued her clinical practice and also conducted research into the impact of genes and the environment on eye disease, with particular reference to the Aboriginal people. She travelled extensively throughout Australia and Oceania studying the incidence of eye disease in different races and cultures. In particular she highlighted the high incidence of trachoma amongst Aboriginal peoples, at a time when it was thought to have been eradicated in Australia. She was incredibly hard-working and insatiably curious, and continued working and exploring into old age. She was appointed CBE in 1950 and DBE in 1980. She died at her home in Perth in 1983.