1. 1Department of Ophthalmology, The Second Hospital of Jilin University, Changchun 130041, P. R. China
2. 2Department of Vascular Surgery, The China-Japan Union Hospital of Jilin University, Changchun 130033, P. R. China
3. 3St Erik's Eye Hospital, Karolinska Institutet, Polhemsgatan 50, SE-112 82, Stockholm, Sweden