1. Capital Medical University, Beijing Ophthalmology & Visual Science Key Laboratory; Beijing Tongren Eye Center, Beijing Tongren Hospital; No.1 Dongijiaominxiang Dongcheng District Beijing China 100730
2. School of Public Health, Peking University; Centre for Evidence Based Medicine and Clinical Research, Department of Epidemiology and Biostatistics; 38 Xueyuan Road Haidian District Beijing China 100191
3. Capital Medical University; School of Public Health; No.10 West tou-tiao-wai FengTai District Beijing China 100069
4. Johns Hopkins Bloomberg School of Public Health; Department of Epidemiology; 615 N. Wolfe Street Baltimore Maryland USA 21205