1. Department of Optometry, School of Physics, College of Sciences and Health, Dublin Institute of Technology, Kevin Street, Dublin 8, Ireland; and African Vision Research Institute
2. Brien Holden Vision Institute, Public Health Division, 172 Umbilo Road, Durban, 4000, South Africa
3. Lúrio University, Bairro de Marrere, R. number 4250, Km 2,3, Nampula, Mozambique
4. Department of Optometry, School of Physics, College of Sciences and Health, Dublin Institute of Technology, Dublin, Ireland
5. Brien Holden Vision Institute, Public Health Division, Durban, South Africa