He specialised in the management of retinal diseases, especially diabetic retinopathy and age-related macular degeneration, the commonest causes of sight threatening problems. In addition, he spent many years as an examiner for the Royal College of Ophthalmologists, eventually becoming Senior Examiner and chair of the College Examinations Committee. He was also Director for Examinations of the International Council of Ophthalmology, organising the assessment of ophthalmologists across the world as well as working as a performance assessor for the General Medical Council.
Simon is also interested in vision and driving, having worked as chair for the Ministry of Transport Medical Advisory Committee for Vision and Driving. He is well aware of the impact the loss of a driving licence can have for people affected with sight-threatening diseases. He also worked for a while for the International Paralympic Committee in assessing visually impaired competitors for their individual classification group.