Comparison between binocular therapy and patching for treatment of amblyopia:a meta-analysis of randomised controlled trials

Authors: Chen CW, Zhu Q, Duan YB, Yao JY.

Geographical coverage: Not reported

Sector: Treatment

Sub-sector: Supplementary therapy

Equity focus: Children with amblyopia

Study population: Children aged between 3 and 17 years old.

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Several studies have compared binocular therapy and patching for the treatment of amblyopia. However, most of them involved a small number of cases and reported controversial results. Thus, the benefit of binocular therapy remains to be confirmed.

Objectives: To evaluate the efficacy of binocular therapy versus patching and to testify whether binocular therapy could become supplementary method in children with amblyopia.

Main findings:

Authors included and analysed six randomised controlled trials (RCTs) comparing binocular therapy (708 eyes) with patching (664 eyes) for change in best-corrected visual acuity and stereoacuity. 304 participants underwent binocular therapy and 332 were treated with patching.

Authors found best-corrected visual acuity in the binocular group was better than that in the patching group (SMD = -0.21 logarithm of the minimum angle of resolution (logMAR), 95% CI of -0.50 to 0.08 logMAR, p = 0.003). They further note that results showed statistically significant difference in the change of best-corrected visual acuity between the groups, but not in stereoacuity. Binocular therapy may be a promising treatment of conditions affecting visual acuity and could be applied as a supplementary method to patching for amblyopia in clinical practice.

Sensitivity analysis found limited difference between trials in BCVA, indicating that the results were relatively stable, according to the authors. Authors acknowledged that one study, in which the inappropriate randomisation was found, had influenced the data analysis. Publication bias was not detected by the statistical tests. Authors acknowledged the diversity of binocular therapies in studies resulted in poor weight on the funnel plot.

Authors note that further RCTs with larger sample sizes and longer treatment durations are warranted to assess efficacy in treating amblyopia and disease recurrence.

Methodology:

The inclusion criteria consisted of RCTs that enrolled participants of age 3-17 years; diagnosis of strabismic, anisometropic and combined amblyopia; BCVA worse than 20/50 for ages 3-4, 20/40 for ages 4-5, 20/30 for ages 5 or more; no previous amblyopia therapy (for example, patching, atropine, Bangerter and vision therapy) in the past two weeks; absence of ocular pathology; no prior surgery; absence of systemic disease; and absence of Down syndrome or cerebral palsy. Studies with primary data, involving at least two weeks of binocular therapy with patching or not in one group, patching with placebo binocular iPad game or patching in the other one, were included. Primary outcome measured was the best-corrected visual acuity (BCVA) and the secondary outcome measured was stereoacuity.

The PubMed, Ovid, Ovid EMBASE, the Cochrane Library and Web of Science databases were systematically searched by the authors for articles published in English from their inception to 22 May 2020. Authors further note screening the Cochrane Library, ClinicalTrials.gov, and the WHO International Clinical Trials Registry Platform for relevant electronic studies of RCTs related to amblyopia. The electronic database search was supplemented by a manual search of the reference lists of included articles.

Two authors independently screened studies for inclusion, extracted data using a standardised collection form, and assessed the quality of studies using the Cochrane risk-of-bias tool for RCTs.

Study authors conducted a meta-analysis of RCTs. They calculated summary estimates, including 95% CIs, mean and SD (mean±SD), p value, and Z-value. For continuous outcomes data (for example, BCVA), the means and SD were used to calculate the standard mean difference (SMD) between groups, where p <0.05 was regarded as statistically significant. For analysis, statistical heterogeneity was tested using the χ² test and I² statistic. Subsequently, authors considered performing sensitivity and subgroup analyses by follow-up duration or age to investigate the source of the severe heterogeneity when applicable (I² >50%). Both Begg’s and Egger’s linear regression tests were performed to assess publication bias. Following the detection of publication bias, authors used the trim and fill method to determine the stability of the results.

Applicability/external validity:

Authors do not explicitly discuss the applicability or external validity of review findings. However, they acknowledge that due to the limitations of included studies and between-study heterogeneity which limits the generalisability of findings.

Geographic focus: Authors do not provide geographical coverage of included studies.

Summary of quality assessment:

Important limitations were identified in the methods used in this review. The search methodology was not exhaustive enough to guarantee the inclusion of all pertinent studies in the review: there was no strategy to circumvent language bias, and no outreach was made to authors or experts for potentially relevant trials. In addition, the authors did not disclose the quality of each trial included and did not perform a statistical analysis contingent on the quality of the trials. However, they did partially recognize the limitations of the studies included and investigated the variability among them. Therefore, a medium confidence was attributed in conclusions of this review.