Funding for this research was provided by:
Tianjin Municipal Health Bureau Youth Fund (no.2012KY37, no 2012KG124)
Received: 22 September 2016
Accepted: 29 May 2018
First Online: 8 June 2018
Ethics approval and consent to participate
: This study was approved by the ethics committees of Tianjin Central Hospital of Gynecology Obstetrics (Tianjin, China) and Tianjin Eye Hospital (Tianjin, China). All participants in this study provided written, informed consent to participate.
: The authors declare that they have no competing interests.
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