1 NIHR Biomedical Research Centre at Moorfields Eye Hospital National Health Service Foundation Trust, London EC1V 2PD, UK; Institute of Ophthalmology, University College London, London, UK. Electronic address: g.gazzard@nhs.net.
2 NIHR Biomedical Research Centre at Moorfields Eye Hospital National Health Service Foundation Trust, London EC1V 2PD, UK; Institute of Ophthalmology, University College London, London, UK.
3 Department of Statistical Science, University College London, London, UK.
4 The Research Department of Primary Care and Population Health, University College London, London, UK.
5 The Research Department of Primary Care and Population Health, University College London, London, UK; Marie Curie Palliative Care Research Department, University College London Division of Psychiatry, University College London, London, UK.