Li Dai1, Ai-Ling Li2, Ling Yu1,3, Jian Ye3. 1. Department of Ophthalmology, the Affiliated Hospital of Southwest Medical University, Luzhou 646000, Sichuan Province, China. 2. Department of the School of Public Health of Southwest Medical University, Luzhou 646000, Sichuan Province, China. 3. Department of Ophthalmology, Daping Hospital, Army Medical University, Chongqing 400042, China.