Professor O’Leary is recognized internationally for his clinical and research activities in ear disease, hearing and balance, and particularly for contributions to cochlear implantation. His primary translational research is the protection of the inner ear during cochlear implant surgery, which promises to enable implant recipients to maintain their hearing in the ear that receives the cochlear prosthesis. He has a track record in the aetiology and prevention of infection with cochlear implantation, and the use of neurotrophins to regenerate the auditory nerve after deafness. Professor O’Leary has led the development of a virtual reality simulator to train ear surgeons in collaboration with CSIRO, and this system has recently been licensed for commercial development to an Australian company, Medic Vision. He was elected to the Collegium Otorhinolaryngologicum Amitciae Sacrum in 2006 in recognition of his contributions to Otolaryngology, and was recipient of the 2009 John Mitchell Crouch Fellowship of the Royal Australasian College of Surgeons for excellence in surgical research.