[1] Univ Calif San Francisco, FI Proctor Fdn, San Francisco, CA 94143 USA
[2] FSS Univ Abdou Moumouni Niamey, Programme Natl Lutte Cecite, Niamey, Niger
[3] Zinder Hosp, Zinder, Niger
[4] Johns Hopkins Univ, Wilmer Eye Inst, Dana Ctr Prevent Ophthalmol, Baltimore, MD 21218 USA
[5] London Sch Hyg & Trop Med, Dept Infect & Trop Dis, London WC1, England
[6] Univ Calif San Francisco, Inst Global Hlth, Dept Med, San Francisco, CA 94143 USA