1. From the Shenyang He Eye Hospital, Shenyang, China;
2. the Zhongshan Ophthalmic Center, State Key Ophthalmic Laboratory and Preventive Ophthalmology Unit, Sun Yat Sen University, Guangdong, People's Republic of China;
3. the International Centre for Eye Health, London School of Hygiene and Tropical Medicine, London, United Kingdom; and
4. the Chinese University of Hong Kong, School of Public Health, Shatin, Hong Kong SAR.