1. Department of Ophthalmology, College of Medicine, Chungbuk National University, Cheongju, Republic of Korea
2. Department of Ophthalmology, Gangneung Asan Hospital, University of Ulsan, College of Medicine, Gangneung, Republic of Korea
3. Department of Clinical Epidemiology and Biostatistics, Asan Medical Center, University of Ulsan, College of Medicine, Seoul, Republic of Korea
4. Department of Ophthalmology, Asan Medical Center, University of Ulsan, College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 138-736, Republic of Korea