1 School of Human and Health Sciences, University of Huddersfield, Queensgate, Huddersfield, UK.
2 NHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK.
3 Reader in Medical Statistics, Department of Primary Care & Public Health Sciences, King's College London, 4th Floor, Addison House, Guy's Campus, London, SE1 1UL.
4 Comprehensive Clinical Trials Unit, University College London, London, UK.
5 Medical School, University College London, London, UK.