1. From the London School of Hygiene and Tropical Medicine, London, United Kingdom;2Medical Research Council Laboratories, Fajara, The Gambia; the
2. Medical Research Council Laboratories, Fajara, The Gambia; the
3. From the London School of Hygiene and Tropical Medicine, London, United Kingdom;
4. National Eye Care Program, Banjul, The Gambia; the
5. Dana Centre for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland; and the
6. From the London School of Hygiene and Tropical Medicine, London, United Kingdom;5Division of Epidemiology and International Eye Health, Institute of Ophthalmology, London, United Kingdom.