1. University of Nottingham, Faculty of Engineering, Division of Electrical Systems and Optics Research, University Park, Nottingham NG7 2RD, United Kingdom
2. University of Glasgow, School of Physics and Astronomy, Kelvin Building, University Avenue, Glasgow, G12 8QQ, United Kingdom
3. Heriot–Watt University, School of Engineering and Physical Sciences, Edinburgh EH14 4AS, United Kingdom
4. Gloucestershire Hospitals NHS Foundation Trust, Cheltenham General Hospital, Gloucestershire Eye Unit, Department of Ophthalmology, Cheltenham GL53 7AN, United Kingdom