Limitations
anxiety
This study has some limitations. Firstly, the study was not double blinded. However, the outcomes were generated on objective measurements by experienced professionals, likely minimizing this observation bias. Secondly, the duration of study was 12 months, not a very long term for a clinical trial. Nevertheless, the results were reliable and significant. A longer-term trial has been planned in our group. Thirdly, this study did not include a long-term withdrawal period for children who continued to use Orth-K for 12 months. Therefore, further investigation is needed to confirm the rebound effect at a longer term. Fourthly, anxiety among Chinese parents, unwillingness to join the investigation, and uncooperative patient attitude were other factors affecting this study. However, this effect was very limited since not many children were withdrawn during this study due to our extraordinary effects to complete this investigation.