About the Authors

Robert Lindfield

Robert.lindfield@lshtm.ac.uk

Affiliation International Centre for Eye Health, London School of Hygiene and Tropical Medicine (LSHTM), London, United Kingdom

Ulla Griffiths

Affiliation Department of Global Health and Development, London School of Hygiene and Tropical Medicine (LSHTM), London, United Kingdom

Fiammetta Bozzani

Affiliation Department of Global Health and Development, London School of Hygiene and Tropical Medicine (LSHTM), London, United Kingdom

Musonda Mumba

Affiliation Lusaka Eye Hospital, Lusaka, Zambia

Joseph Munsanje

Affiliation S & S Development Consultants, Lusaka, Zambia

Competing Interests

One author is currently employed by S&S Development Consultants; however, at the time of the data collection he was employed by Sightsavers International (the funding agency) to oversee the survey. Since working for S&S Development Consultants he has commented on the draft paper. This does not alter the authors’ adherence to all the PLoS ONE policies on sharing data and materials.

Author Contributions

Conceived and designed the experiments: RL JM. Performed the experiments: RL MM. Analyzed the data: RL UG FB JM. Wrote the paper: RL UG FB MM JM.