Methodological quality of the review: Medium confidence
Authors: Yanhui Cui, Li Li, Qian Wu, Junyang Zhao, Huihui Chu, Gang Yu, Wenbin Wei
Region: China, Hong Kong, Malaysia, Nepal, Cambodia, Vientiane, India, Iran, Australia, Finland, UK, South Africa, Chile, Poland, USA, Mexico, Sweden
Subsector: Myopia correction
Equity focus: No
Study population: Children
Type of programme: School based
Review type: Other review
Quantitative synthesis method: Meta-analysis
Qualitative synthesis method: Not applicable
Background: Refractive errors that are uncorrected are a leading cause of visual impairment worldwide and myopia is the most common refractive error. It has been estimated that up to 30 per cent of the United States’ population and over 90 per cent of some East Asian populations are affected by myopia. Myopia is typically progressive in children and early onset myopia can be associated with the development of high myopia, which can result in a large number of pathological complications. Myopia is typically caused by increased axial length of the eye which causes light from objects at a distance to focus in front of the retina, resulting in blurred distance vision. Many approaches have been examined to treat and/or slow the progression of myopia. However, there remains no consensus on the best method to control myopia progression. Few studies have compared the two methods, or compared RGP lenses with other methods of myopia control.
Objectives: The aim of this study was to conduct a meta-analysis comparing RGP and soft contact lenses (SCL) and spectacles, and RGP and OK lenses for myopia control with respect to axial length elongation, spherical equivalent and measures of corneal curvature.
Main findings: Five studies were included. Three studies reported axial length change after two to three years of treatment with RGP lenses and SCL/spectacles, and no difference between the groups was noted (pooled mean difference = -0.077, 95% confidence interval [CI]: -0.120 to 0.097, P=0.840). Two studies reported a change of spherical equivalent after two to three years of treatment with RGP lenses and SCL/spectacles, and no difference between the groups was noted (pooled mean difference = 0.275, 95% CI: -0.390 to 0.941, P=0.417). Two studies compared corneal curvature measures between RGP and OK lenses after three to six months of treatment, and no differences in any measures of corneal curvature were seen.
Based on these findings, authors conclude that the effect of RGP lenses and SCL/spectacles on axial length elongation and spherical equivalent and of RGP and OK lenses on corneal curvature in children with myopia was similar.
Methodology: Inclusion criteria included: 1) randomised controlled trials (RCTs), two-arm prospective studies and retrospective studies; 2) examined children with myopia; and 3) outcomes with RGP lenses, compared with those of other treatments, such as spectacles, SCL and OK lenses, were reported. Cohort studies, letters, comments, editorials, case reports, proceedings, personal communications and one-arm studies were excluded, as were studies that did not provide quantitative outcome data. This systematic review and meta-analysis was conducted in accordance with PRISMA guidelines. Medline, the Cochrane Library, Embase and Google Scholar databases were searched by authors from inception to 29 September 2015. Reference lists of relevant studies were also searched for potentially relevant articles. Searches were conducted independently by two reviewers, and a third was consulted for resolution of any disagreements. The methodological quality of the included studies was assessed using the risk-of-bias assessment tool outlined in the Cochrane Handbook for Systematic Reviews of Interventions. Authors compared outcomes between patients who wore RGP lenses and those who wore SCL or spectacles, and those who wore RGP lenses and OK lenses. Pooled mean differences with 95% confidence intervals (CIs) were calculated. Heterogeneity between studies was evaluated using the Cochran Q statistic and the I2 statistic, which indicates the percentage of the observed between-study variability caused by heterogeneity. A Cochran Q statistic with a value of P<0.1 or I2 statistic >50% was considered to indicate significant heterogeneity. All statistical analyses were performed by using Comprehensive Meta-Analysis software, version 2.0 (Biostat, Englewood, NJ, USA).
Applicability/external validity: Regarding external validity, the authors reported some limitations which need to be considered: the first of which is the small number of available studies to be included. Time points of outcome measurement varied between some studies, and in some studies the drop-out percentage was not reported. This analysis was limited to comparing the results of certain types of optical correction methods and did not examine pharmacological methods.
Geographic focus: Not discussed.
Summary of quality assessment:
Authors used rigorous and appropriate methods to analyse data of included studies, to search for literature and screen studies for inclusion. However, literature searches were not comprehensive enough to ensure that all potentially relevant studies were identified, in addition, authors did not search for grey literature and did not avoid language bias. Therefore, there is medium confidence in the conclusions about the effects of this study.