[1] Royal Liverpool Univ Hosp, St Pauls Eye Unit, Liverpool L7 8XP, Merseyside, England
[2] Coll Med, Malaria Project & Wellcome Trust Res Labs, Blantyre, Malawi
[3] Michigan State Univ, Coll Osteopath Med, E Lansing, MI 48824 USA
[4] Univ Liverpool, Sch Trop Med, Liverpool L69 3BX, Merseyside, England