This study has several limitations. First, our analysis was based on only seven studies (two RCTs and five non-RCTs) with relatively small sample sizes, thus limiting the reliability of the results. Second, the targeted population varied greatly, and study protocols and designs differed. These factors may have potential effects on our results. Third, the study by Walline et al.15 was included in this meta-analysis, although soft contact lenses were used as control. Moreover, most trials included in the present meta-analysis were performed in Asia, and only two studies15,17 were conducted outside this region in America and Spain.
Further studies should focus on the following two points. First, although RCTs for orthokeratology are difficult to carry out, using RCTs can leave little room for bias, and the results of RCTs are more convincing. Therefore, future large-scale RCTs to investigate the effects of orthokeratology on myopia progression are still important. Second, because the mechanism of myopia progression is still debatable, additional animal and human studies will be needed to further elucidate the potential biological mechanisms that are involved.
This study was supported by the National Natural Science Foundation of China (81173440) and the Shandong Traditional Chinese Medicine Science and Technology Development Plans Project (2011-130). Jun-Kang Si and Kai Tang contributed equally to this work.
Received February 17, 2014; accepted October 10, 2014.
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