1. 1Francis I Proctor Foundation, University of California, San Francisco, California;
2. 2Centre de Recherche en Santé de Nouna, Nouna, Burkina Faso;
3. 3Centre de Recherche et Interventions en Santé Publique, Niamey, Niger;
4. 4Department of Ophthalmology, University of California, San Francisco, California;
5. 5Department of Epidemiology & Biostatistics, University of California, San Francisco, California