1. Division of Hematology and Oncology, Department of Internal Medicine; Gachon University Gil Medical Center; Incheon Korea
2. Department of Ophthalmology, Kangbuk Samsung Hospital; Sungkyunkwan University School of Medicine; Seoul Korea
3. Department of Statistics; Dongguk University; Seoul Korea
4. Department of Family Medicine; Gachon University Gil Medical Center; Incheon Korea