His area of specialisation is Electron Microscopy and he is a co-author of several neuroscience papers. Dr O'Leary is actively involved in the Biosciences Imaging Centre - a specialist microscopy facility run by the Department of Anatomy & Neuroscience providing training and Microscopy services to researchers and industry.

Dr O'Leary holds a PhD in History and his published work includes three books, focusing mainly on the response of the Roman Catholic Church to scientific developments from the mid-nineteenth century to recent years.