Peter B M Thomas1, Chrishan D Gunasekera2. 1. NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, EC1V 9EL, UK. pbmthomas@gmail.com. 2. Department of Ophthalmology, West Suffolk Hospital, Bury St Edmunds, UK.