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