Roseline Ekanem Duke1,2, Justin Nwachukuw3, Chima Torty4, Uche Okorie3, Min J Kim5, Kathryn Burton6, Clare Gilbert7, Richard Bowman8. 1. Ophthalmology, Calabar Children's Eye Centre, University of Calabar Teaching Hospital, Calabar, Cross River, Nigeria dr.roselineduke@gmail.com. 2. Clinical Research Unit, ITD, International Centre for Eye Health, London School of Hygiene and Tropical Medicine Faculty of Infectious and Tropical Diseases, London, London, UK. 3. Ophthalmology, Calabar Children's Eye Centre, University of Calabar Teaching Hospital, Calabar, Cross River, Nigeria. 4. Pediatric Neurology, University of Calabar Teaching Hospital, Calabar, Cross River, Nigeria. 5. Tropical Epidemiology Group, Faculty of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, London, UK. 6. Community Paediatrics, Cambridgeshire Community Services NHS Trust, Saint Ives, Cambridgeshire, UK. 7. Clinical Research Unit, ITD, London School of Hygiene and Tropical Medicine Faculty of Infectious and Tropical Diseases, London, London, UK. 8. International Centre for Eye Health, London School of Hygiene and Tropical Medicine Faculty of Infectious and Tropical Diseases, London, London, UK.