The preliminary study of screening for fundus diseases with digital nonmydriatic fundus camera among residents of 50-year-old or elder in 2 communities in Beijing 
HAN Cui, Xu-Qing, LIU Ning, FENG Hui-Ping, HOU Bao-Jie, WU Hai-Yang
Ophthalmology in China . 2013, (4): 230 -233 .