Efficacy and safety of different add power soft contact lenses on myopia progression in children: a systematic review and meta-analysis

Authors: Yu Z, Zhong A, Zhao X, Li D, Duan J.

Geographical coverage: Spain, China, Hong Kong, USA, New Zealand and Japan.

Sector: Biomedical

Sub-sector: Treatment

Equity focus: Children

Study population: School-age children aged 6-18 years with myopia.

Review type: Effectiveness review

Quantitative synthesis method: Systematic review and meta-analysis

Qualitative synthesis method: Not applicable

Background: Myopia in children is a significant global health issue. Soft multifocal contact lenses (SMCLs) have been extensively researched for controlling myopia progression in children. However, questions remain about their effectiveness, safety, and the impact of different added power SMCLs. Previous systematic reviews and meta-analyses have evaluated the effectiveness of SMCLs, but they did not investigate variations in efficacy across different add powers or conduct a quantitative assessment of adverse effects and acceptability.

Objectives: Evaluate the efficacy and safety of various add power SMCLs to slow myopia progression in children.

Main findings:

Overall findings of this review found that high add power SMCLs are more effective and stable to control myopia progression. Besides, the adverse effects and acceptability were not related to the added power.

A total of 805 children younger than 18 were included, including 346 Asians and 459 white individuals. One study of low added power contact lenses, two of medium added power contact lenses, and six of high added power contact lenses were included, yielding nine experimental groups in seven studies. Two studies were conducted in Spain, one in China, one in Hong Kong, one in the USA, one in New Zealand and one in Japan.

All trials reported adequate randomisation methods, the number of participants lost to follow-up, and completeness of outcome indicators, comprehending a low risk of bias. All trials reported blinding, with five studies blinded to outcome measures and two blinded to subjects and investigators, leading to a low risk of bias. Four studies did not describe allocation protocol concealment and had some risk of bias. Seven studies had other unclear biases, comprehending some risk of bias. Overall, the quality of the RCTs included was high.

Seven independent studies involving 805 children were included in the present meta-analysis. At 1-year, the weighted MD (WMD) in myopia progression between SMCL and control groups was -0.22 dioptres (D) (95% confidence interval [CI]: -0.56 to 0.12 D) for low add power SMCLs, 0.09 D (95% CI: 0-0.19 D) for medium add power SMCLs, and 0.2 D (95% CI: 0.13, 0.27 D) for high add power SMCLs. At 2-years, the WMD for medium add power was 0.12 D (95% CI: -0.03 to 0.27 D), and for high add power was 0.25 D (95% CI: 0.14-0.35 D). No differences were detected for adverse effects (p = 0.2) and acceptability (p = 0.74) between different added powers. Additionally, differences in visual performance changes, produced by different added powers, were not detected.

The axial length data revealed heterogeneity, and the sensitivity analysis indicated that Walline’s study might have been the source of the heterogeneity.

Methodology:

Studies were selected based on the following criteria: (1) study type: randomised controlled trials (RCTs); (2) participants: school-age children (6-18 years) with myopia; (3) intervention: SCL experimental groups in a multifocal design with specific add powers and monovision soft contact lenses or glasses in control groups; and (4) outcomes: myopic progression (change in spherical equivalents) as the primary outcome and axial elongation (axial length changes) as the secondary outcome. Two authors independently assessed the titles and abstracts of all retrieved studies.

Authors searched the PubMed, Medline, EMBASE and the Cochrane Central Register of Controlled Trials databases for relevant studies from inception to 10 July 10 2021, using medical subject headings (MeSH) and free words combining “myopia”, “contact lens” and “RCTs”. They also screened ClinicalTrials.gov and the reference list of published reviews to identify additional relevant studies. The Boolean operators “AND”, “OR” and “NOT” were used to combine all search sets.

Two authors screened titles and abstracts to independently and repeatedly identify potentially eligible articles. Then, they examined the full text to determine the final inclusion. For included studies, two reviewers independently extracted study characteristics (authors, year, country or region, study design, follow-up time, interventions and controls, added power), patient characteristics (age, mean change in cycloplegic spherical equivalents, mean axial elongation changes, number of adverse events and dislocations), and relevant information regarding the methods. For continuous data, SER and axial length change values were included and are expressed as means and SDs. For categorical data, the number of each group was extracted. For missing data, the GetData Graph Digitizer 2.25 (http://getdata-graph-digitizer.com) was used for figures illustration only, if needed. Discrepancies were adjudicated by a third reviewer.

Quality assessment: The risk of bias for the selected trials was assessed according to six aspects of the Cochrane Collaboration: sequence generation, allocation concealment, blinding, incomplete outcome information, selective outcome reporting and other sources of bias. The risk of bias for each aspect was graded as “low”, “unclear” or “high”.

Statistical analyses: Data analyses were performed using Review Manager (version 5.4; Cochrane Collaboration) and Stata (version 16.0; StataCorp). A comparative study analysis was performed based on the changes in contact lenses with different added powers versus control groups. The weighted mean difference (WMD) and 95% confidence intervals (CIs) were calculated for different contact lens added powers in refractive changes and axial elongation versus control groups. Also analysed were the odds ratio for adverse effects and the number of dislocations between SMCLs and control groups, and these were presented as forest plots. Statistical heterogeneity between studies was tested using the χ2 test, Tau², and I², and a p <0.1 was considered significant. Larger Tau² and I² indicated greater heterogeneity. If significant heterogeneity existed, estimates were calculated using a random-effects model. Otherwise, a fixed-effects model was used. Sensitivity analysis was conducted by excluding literature with significantly different characteristics. Subgroup analyses were performed by heterogeneity across ethnicity (Asian vs. White individuals) and contact lens designs. Since 10 trials were included, funnel plots were used to check for publication bias and to analyse the symmetry.

Applicability/external validity: Authors noted study limitations, which may impact on the validity and external validity of findings of the review such as: 1) RCTs only included, limiting the investigation of each add power SMCL due to insufficient studies, 2) incomplete reporting of adverse affects, and 3) exclusion of studies without clear add value of SMCLs.

Geographic focus: The study incorporated two low- and middle-income countries, namely China and Hong Kong. The research spanned across multiple countries with two studies in Spain, and one each in China, Hong Kong, the USA, New Zealand, and Japan. Despite this geographical diversity, the authors were unable to categorize the findings based on geographic regions.

Summary of quality assessment:

The approaches undertaken to identify, include and critically appraise studies were generally rigorous, however, the search was somewhat limited in that it did not include unpublished material or material published in languages other than English. While the approaches undertaken to the extraction and analysis of the data were generally rigorous, no mention was made of unit of analysis errors – which we feel it would have been appropriate to consider, given the inclusion of RCTs. For these reasons, we have medium confidence in the findings of this review.