1. Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, P.R. China
2. Hunan University of Finance and Economics, Changsha, Hunan 410205, P.R. China
3. Health Management Center, The Third Xiangya Hospital, Central South University, Changsha, Hunan 410013, P.R. China