Treatment effect of posterior scleral reinforcement on controlling myopia progression: A systematic review and meta-analysis

Authors: Chen CA, Lin PY, Wu PC.

Geographical coverage: China, USA

Sector: Biomedical

Sub-sector: Treatment of myopia

Equity focus: None specified

Study population: People with myopia

Review type: Other review

Quantitative synthesis method: Systematic review and meta-analysis

Qualitative synthesis method: Not applicable

Background: High myopia is a sight-threatening disease that causes axial length elongation and severe complications. Data on the benefits of posterior scleral reinforcement surgery in myopia control has been conflicting.

Objectives:

The purpose of this study was to explore the treatment effect and complications of posterior scleral reinforcement in the treatment of myopia.

Main findings:

Authors included a total of 11 studies in the meta-analysis, including one RCT and 10 cohort studies. The operation methods were single wide strip (n = 9) and X-type PSR (n = 2). Among these studies, six were self-control studies using the fellow eye as controls, and five studies compared PSR versus a control group without PSR treatment. The quality of the cohort studies and RCT was generally good, as reported by the authors.

The pooled analysis of one RCT and eight cohort studies in the two-arm meta-analysis, showed significantly less refraction progression in PSR group (MD = 0.41 dioptre per year, 95% CI 0.21 to 0.61; p <.001). The Hedges’ analysis showed large treatment effect. By subgroup analysis, single wide strip was effective on controlling refraction progression but X-type operation was not. A significantly high heterogeneity was noted in the refraction progression when pooling the RCT and cohort studies (p <.001, I² = 86%). Authors found heterogeneity to be associated with age. Heterogeneity on refraction progression were significant among single wide strip operation, X-type operation, children and adults.

Methodology:

Authors performed a broad and comprehensive literature search from Pubmed, EMBASE, and Ovid for studies published from the date of inception to 24 July 2019. They also searched for the references of included studies.. Two authors independently screened studies for inclusion in the review based on the following criteria: (1) comparison study including randomised clinical trials (RCT), cohorts, or non-RCT design studies; (2) the participants had myopia without retinoschisis, macular hole, or retinal detachment; (3) studies that estimate the effect of PSR operation on controlling myopia progression; and (4) the studies reported outcomes of spherical equivalent refraction (SER) or axial length (AXL). The exclusion criteria were: (1) repeats; (2) the articles failed to report relevant data to calculate the values; (3) non-human studies; and (4) reviews, letters or comments.

Two reviewers independently extracted data of included studies such as publication year, study design, country, patient ages, sample size, intervention and control methods, and/or standard deviation (SD), and number of adverse effects. For postoperative complications analysis, studies with defined specific complication items were included. Authors imputed missing data by estimating the covariance (Cov) and correlation coefficient (r) reported by other studies in this meta-analysis, according to the Cochrane Handbook for Systematic Reviews of Interventions. Sensitivity analysis was performed by imputing with an individual r from lower to upper limit each time.

To assess the quality of studies, authors used the Newcastle-Ottawa Scale (NOS) for cohort studies. The Cochrane risk-of-bias tool was applied for RCTs.

The authors conducted two-arm and single-arm meta-analyses. In the two-arm analysis, they compared PSR and control groups, calculating the weighted mean difference (MD) for myopia progression and axial elongation, and presenting the results in forest plots. In the single-arm analysis, they calculated the change-from-baseline SER and AXL outcomes from the PSR group. They used Hedges’ g to calculate the effect size (ES) for each outcome. Heterogeneity was assessed using the I2 statistic. Sensitivity analysis was performed by excluding one study at a time. Subgroup analysis was conducted based on different operation methods and age groups to evaluate variations in effect size. Tests were performed to examine differences among subgroups.

Applicability/external validity:

The authors do not explicitly discuss the applicability of their findings to other settings or populations. However, they do acknowledge some limitations of their study, such as the limited number of studies, the heterogeneity among studies, the lack of long-term follow-up data, and the need for more randomized clinical trials. They also suggest that further studies should report the outcomes according to different operation methods and the children’s age groups. Therefore, the authors imply that their findings may not be generalizable to all cases of high myopia and posterior scleral reinforcement surgery, and that more research is needed to determine the long-term safety and efficacy of this intervention.

Geographic focus: This review includes studies conducted in China and the USA, and authors do not report how findings may be applicable to low- and middle-income settings.

Summary of quality assessment: Low

Overall, authors used appropriate approaches to screen studies for inclusion, extract data and assess the quality of included studies. However important limitations were identified. The searches were not comprehensive enough to ensure that all relevant studies were identified, language bias was not avoided as studies written in English only were included. Therefore, a medium confidence was attributed in the conclusions about the effects of this review.