Orthokeratology for Myopia Control: A Meta-analysis

Methodological quality of the review: Medium confidence

Author: Jun-Kang Si, Kai Tang, Hong-Sheng Bi, Da-Dong Guo, Jun-Guo Guo, and Xing-Rong Wang

Region: Hong Kong, Japan, Spain, USA

Sector: Myopia

Subsector: Myopia control

Equity focus: No

Study population: Children aged 18 years and younger

Type of program: Hospital based

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: High myopia is a risk factor for cataract, glaucoma, myopic retinopathy and retinal detachment. Therefore, it is very important to slow or even stop the progression of myopia in children. Several medical treatments have been considered to suppress myopia progression, including topical application of tropicamide, atropine and pirenzepine. Nevertheless, there have been no ideal therapeutic modalities to effectively prevent myopic progression in light of efficacy, safety, economic feasibility and ease of application. Orthokeratology, an optical correction mainly for correcting low-to-moderate myopia, is showing a potential to reduce the progression of myopia. It is reversible and if the patient is unhappy with the treatment, he or she can simply discontinue wearing the lenses. Therefore, it would be valuable to conduct a quantitative and systematic summary of the evidence using rigorous methods.

Objectives: The aim of this study was to assess the results from published studies on the efficacy of orthokeratology in myopia control.

Main findings: A total of seven studies were included in this review, two RCTs and five non-RCTs published from 2005 to 2013. A total of 435 subjects (orthokeratology group, 218; control group, 217) aged 6 to 16 years were included in the present meta-analysis. The results showed that AL increased with time in both orthokeratology and control subjects. At two years’ follow-up, the AL elongation of the orthokeratology group was significantly slower than that of the control group (WMD, -0.26 mm; 95% CI, -0.31 to -0.21; P<0.001). Two studies reported VCD, which increased with time in both groups of subjects. The VCD changes in the orthokeratology group were significantly slower than those in the control group (WMD, -0.18 mm; 95% CI, -0.33 to -0.03; P=0.02).

Authors conclude that orthokeratology may slow myopia progression in children. Further large-scale studies are needed to substantiate the current result and to investigate the long-term effects of orthokeratology in myopia control.

Methodology:

Inclusion criteria included: 1) controlled clinical trials, including RCTs and non-RCTs; 2) myopic patients aged 18 years and younger; 3) comparison of orthokeratology with control subjects (single-vision spectacles or soft contact lenses); and 4) reporting on AL elongation or more information relevant to myopia progression, for example, vitreous chamber depth (VCD) elongation. Article titles were screened for eligibility by two reviewers (SJK and TK), independently.

PubMed, Embase, and the Cochrane Library were searched by the authors. Reference lists of included trials were also searched by the authors. There were no language or data restrictions in searching trials. Reference lists of included trials were also searched. Two review authors independently extracted the data from articles that met this study’s inclusion criteria. The missing SDs were able to be captured from figures using GetData GraphDigitizer 2.24 (available at http://getdata-graph-digitizer.com/index.php). The methodological quality of the articles was evaluated using the Jadad scale. This study followed the PRISMA statement. Statistical analysis was performed with RevMan 5.2.6 software (Cochrane Collaboration, Oxford, UK). In the present meta-analysis, the effect sizes of each study were presented as weighted mean difference (WMD) with 95% CIs for continuous outcome measures (AL, VCD). The statistical heterogeneity was tested by using the I² statistic.

Applicability/external validity: Regarding external validity, the authors reported some limitations which need to be considered: 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. We also included a study who used soft contact lenses as control. Moreover, most trials included in the present meta-analysis were performed in Asia.

Geographic focus: Most trials included in the present meta-analysis were performed in Asia, and only two studies were conducted outside this region, in America and Spain.

Summary of quality assessment:

Authors used rigorous methods to analyse findings of included studies, screen studies for inclusion and extract data of included studies. However, literature searches were not thorough enough to ensure that all potentially relevant studies were identified.