1 Department of Ophthalmology, Yan'an People's Hospital, Qilipu St., Baota Qu, Yan'an, Shaanxi 716000, China
2 Pathology Unit, Preclinical Department, Faculty of Medicine, Royal College of Medicine Perak, Universiti Kuala Lumpur, No. 3, Jalan Greentown, Ipoh 30450, Perak Darul Ridzuan, Malaysia
3 Department of Ophthalmology, Yan'an University Affiliated Hospital, Yan'an, Shaan'xi Province 716000, China