1. Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan City 333, Taiwan
2. Singapore National Eye Centre, Singapore, Singapore 168751, Singapore
3. DUKE NUS Medical School, Singapore 169857, Singapore
4. Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Illinois Eye and Ear Infirmary, Chicago, IL 60612, USA
5. College of Medicine, Chang Gung University, Taoyuan City 333, Taiwan