1. Division of Ophthalmology, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
2. Biostatistics Unit, Centre for Evidence Based Health Care, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
3. Department of Ophthalmology, University Medical Center Utrecht, Utrecht, The Netherlands
4. Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands