1. School of Public Health, Asrat Woldeyes Health Science Campus, Debre Berhan University, Debre Berhan, Ethiopia;
2. Francis I Proctor Foundation, University of California, San Francisco, San Francisco, California;
3. Department of Ophthalmology, University of California, San Francisco, San Francisco, California;
4. Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, California;
5. Institute for Global Health Sciences, University of California, San Francisco, San Francisco, California