Methodological quality of the review: High confidence
Author: Li SM, Ji YZ, Wu SS, Zhan SY, Wang B, Liu LR, Li SY, Wang NL, Wang JJ.
Region: United States (USA), Hong Kong, China, Taiwan, Japan, Canada and Finland.
Sub-sector: Multifocal lenses, single vision lenses, progression.
Equity focus: School-aged children (6 – 15 years old)
Review type: Effectiveness review
Quantitative synthesis method: Meta-analysis
Qualitative synthesis methods: Not applicable
Myopia in school-aged children is a major public health problem in Asians that has been extensively studied. Multifocal lenses (MLs) are advocated as a substitute for single vision lenses (SVLs) to slow myopia progression in children, but results vary greatly across studies.
To assess the effect of MLs versus the effect of SVLs on myopic progression in children and to determine whether the effect of MLs is different in subgroups, such as those with different baseline refractions and ethnicities.
In total, the authors included nine randomized controlled trials (RCTs), three used interventions with bifocal lenses and six used progressive addition lenses. Two RCTs were conducted in the USA, two in Hong Kong, and one each in mainland China, Taiwan, Japan, Canada, and Finland. One was a crossover trial, from which only results from the first interventional period were included. The studies included 1,464 myopic children aged six to 13 years, of whom 730 were treated with MLs. The length of follow-up varied from six to 36 months, and studies used different powers of near addition lenses. Overall, studies were of good quality.
Findings from the meta-analysis indicated that MLs slowed myopia progression by a mean of 0.25D in school-aged children compared with the used of SVLs. A statistically significant difference was observed in the change of refraction levels between MLs and SVLs arms (95% CI 0.13-0.38; p <0.0001). The benefit was greater in children with higher level of myopia at baseline and sustained for a minimum of 24 months. Asian children appeared to have greater benefit from intervention with MLs than white children. Across the nine studies, heterogeneity was found and remained after excluding studies from analysis. The authors noted that remaining questions need to clarified by future RCTs, which include determining an optimal treatment period, how long the effect can last after intervention stops, and whether customized near addition lenses are more effective.
Inclusion criteria consisted of RCTs either parallel in treatment and control arms or crossover design; participants were school-aged children (between six and 15 years), children with myopia, bifocal or progressive lenses were used in at least one treatment arms and SVLs in another as control; and the primary outcome was change in refractive errors from baseline to the end of the intervention period, with or without data available on secondary outcome, which was a change in axial length over the same study period.
Two reviewers independently searched Medline, Embase and the Cochrane Library from inception to 2010. No language restrictions were applied. For further trials, authors screened references of retrieved trials and used Science Citation Index to find study reports that were from the identified trials. Corresponding authors were also contacted to obtain missing data/information.
Two reviewers independently screened articles for inclusion, extracted data and assessed quality and risk of bias of included studies. The authors conducted a systematic review and meta-analysis using random-effect models, heterogeneity among studies was evaluated using the X2 and I2 statistics, sensitivity analysis was performed after removing trials that provided extreme findings, and a sub-group analysis was pre-planned to compare the treatment effects among children with different baseline refraction levels, ethnicities and treatment duration.
The authors did not generalize findings from this study, as results yield varied by the levels of myopia and by ethnicities.
The authors included studies from China (upper- and middle-income setting) and other high- income settings, and reported that MLs slowed progression by a mean of 0.25D in school-aged children compared with the use of SVLs. The decrease appeared to be greater in children with greater levels of myopia and in Asians.
Overall, there is high confidence in the conclusions about the effects of this study. The authors conducted thorough searches of published literature avoiding language bias. However, unpublished studies were not part of the search strategy. Nevertheless, the authors acknowledged this as a limitation of the review and performed a funnel plot that did not suggest a strong case of publication bias.
The authors used appropriate methods in terms of study selection, data extraction and assessment of quality and risk of bias. In addition, the methods used to conduct the systematic review and meta-analysis was clear and explicit in the review.