1. Department of Ophthalmology, Makerere University, Kampala P.O. Box 7072, Uganda
2. Department of Ophthalmology, Juba of University, Juba P.O. Box 82, Sudan
3. Global Health Institute, University of Antwerp, 2610 Antwerp, Belgium
4. Department of Biological Science, University of Energy and Natural Resources, Sunyani P.O. Box 214, Ghana
5. Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK