1. Department of Preventive Medicine, College of Medicine, Yonsei University, Seoul 03722, Republic of Korea
2. Clinical Research Institute, Kyung Hee University Hospital at Gangdong, School of Medicine, Kyung Hee University, Seoul 05278, Republic of Korea
3. Department of Management, Policy & Community Health, School of Public Health, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
4. Department of Epidemiology, Human Genetics & Environmental Sciences, School of Public Health, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
5. Department of Health Services Administration, School of Public Health, University of Maryland, College Park, MD 20742, USA
6. Department of Ophthalmology, Kyung Hee University Hospital at Gangdong, Kyung Hee University College of Medicine, Seoul 05278, Republic of Korea
7. Department of Health Services Research, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA