- Correspondence to Dr Liang Xu, Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, 17 Hougou Lane, Chong Wen Men, Beijing 100005, China;
- Received June 10, 2013
- Revised July 24, 2013
- Accepted August 17, 2013
- First published September 7, 2013.
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