1. Department of Medical Education, Taichung Veterans General Hospital, Taichung 407, Taiwan
2. School of Medicine, National Yang-Ming University, Taipei 112, Taiwan
3. Department of Ophthalmology, Taichung Veterans General Hospital, Taichung 407, Taiwan
4. Wilmer Eye Institute, Johns Hopkins University, Baltimore 21287, Maryland, USA
5. Institute of Public Health and Community Medicine Research Center, National Yang-Ming University, Taipei 112, Taiwan
6. School of Medicine, Chung Shan Medical University, Taichung 402, Taiwan