1. Division of Optometry and Visual Science, School of Health Science, City, University of London, London, England
2. International Centre for Eye Health, Faculty of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK
3. Department of Ophthalmology, Kilimanjaro Christian Medical Centre, Moshi, Tanzania
4. Eye Center, University Hospital Freiburg, Freiburg, Germany