- Correspondence to Dr Ching-Yu Cheng, Saw Swee Hock School of Public Health, National University of Singapore, Singapore Eye Research Institute 1E Kent Ridge Road, NUHS Tower Block Level 7, Singapore 119228, Singapore;
- Received July 2, 2012
- Revised January 23, 2013
- Accepted January 30, 2013
- First published February 22, 2013.
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