1. Department of Ophthalmology, Hamad Medical Corporation, Doha, Qatar.
2. School of Life and Health Sciences, Aston University, Birmingham, UK.
3. Department of Medical Statistics & Epidemiology, Hamad Medical Corporation, Doha, Qatar.
4. Department of Public Health, Weill Cornell Medical College, Doha, Qatar.
5. Department Evidence for Population Health Unit, School of Epidemiology and Health Sciences, The University of Manchester, Manchester, UK.