Dr O’Day completed his graduate medical degree with honours at The University of Sydney in 2011. Prior to this he studied Law and Science at the University of Melbourne.

He began ophthalmology specialist training at Melbourne's Royal Victorian Eye and Ear Hospital (RVEEH) in 2014 and finished in 2018. He then trained as a subspecialist in medical retina (fellowship at RVEEH, 2018) and in ocular oncology (fellowship at Moorfields Eye Hospital in London, 2019).  

He has an active research interest, publishing regularly in the medical literature in his areas of specialisation and presenting at international and local scientific meetings.

As a consultant ophthalmologist, Dr O’Day has public hospital appointments at RVEEH (Ocular Oncology and General Ophthalmology), the Royal Children's Hospital (Ocular Oncology) and University Hospital Geelong (General Ophthalmology). This involves providing public health care and he is actively involved in training future colleagues.