[1] Univ Oxford, Hlth Econ Res Ctr, Nuffield Dept Populat Hlth, Oxford, England
[2] Univ Bristol, Sch Clin Sci, Clin Trials & Evaluat Unit, Bristol, Avon, England
[3] Swiss Re Serv Ltd, Res & Dev, London, England
[4] Univ Southampton, Southampton, Hants, England
[5] Univ Liverpool, Inst Ageing & Chron Dis, Dept Eye & Vis Sci, Liverpool L69 3BX, Merseyside, England
[6] Univ Southampton, Fac Med, Acad Unit Clin & Expt Sci, Southampton SO9 5NH, Hants, England
[7] Oxford Univ Hosp NHS Trust, Oxford Eye Hosp, Oxford, England
[8] Queens Univ Belfast, Ctr Med Expt, Belfast, Antrim, North Ireland