Robert G Peden MBBS (Lond) MA (Oxon) FRCOphth Consultant Ophthalmologist, Princess Alexandra Eye Pavilion; Honorary Clinical Senior Lecturer, University of Edinburgh, UK H Nikki Hall MBChB BSc (Hons) FRCOphth Consultant Ophthalmologist, Queen Margaret Hospital, Dunfermline, Fife; Honorary Clinical Tutor, University of Edinburgh, UK