Methodological quality of the review: Low confidence

Author: Anne Suhr Thykjær, Kristian Lundberg, Jakob Grauslund

Region: USA, Finland, Jordan, Denmark, UK, Ireland, Australia

Sector: Myopia

Subsector: Role of physical activity in myopia development and progression

Equity focus: No

Study population: Children

Type of programme: School based

Review type: Other review

Quantitative synthesis method: Systematic review

Qualitative synthesis method: Not applicable

Background: Myopia is the most common eye disorder. The prevalence varies widely in relation to age, race, ethnicity, urbanisation, educational level and occupation. The increasing prevalence of myopia is considered a major public health challenge, and the World Health Organization recognises uncorrected refractive errors as the most prevalent cause of visual impairment globally. The increasing challenges caused by myopia have attracted attention to the aetiology and potential preventive interventions. A degree of confusion has been introduced because some studies have not distinguished between PA (such as sports, exercise and motor-performance) and time spent outdoors. A negative association has been demonstrated between outdoor activity/time spent outdoors and prevalent myopia. However, we do not know whether the change in refraction is a result of total time spent outdoors per se, rather than the increased physical activity.

Objectives: The aim of this study was to perform a systematic literature review, to examine the association between PA, and the development and progression of myopia.

Main findings: A total of 263 papers were identified in a systematic database search of PubMed/Medline and Embase. Five steps of screening removed studies of a low evidence quality and animal studies. Studies included had refractive error and physical activity (as measured by questionnaires, accelerometers and cycle ergometers) as separate, well-defined outcomes. Nine studies (six cross-sectional, two cohorts and one case-control study) with a total of 17,634 subjects were included. Six studies demonstrated a reverse association between physical activity and myopia. Three studies supported this, but also attributed the results to time spent outdoors and not physical activity per se. One cross-sectional study found no relation. Authors did not identify trends among the papers regarding the type of studies, population sizes, ethnicity or age of study subjects. A consistent relationship between more physical activity and less myopia was observed. No evidence of physical activity as an independent risk factor for myopia was seen. Evidence suggests that time outdoors remains the most important factor.

Methodology: Included studies were required to have PA as a separate variable, and, consequently, studies that failed to examine PA as such were excluded. The study was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA; Moher et al. 2015). Searches were conducted in databases PubMed/Medline and Embase on 26 February 2015. The search was performed to find relevant literature examining a potential effect of PA on the development and/or progression of myopia.

Applicability/external validity: Not discussed.

Geographic focus: Not discussed.

Summary of quality assessment:

Low confidence was attributed in the conclusions about the effects of this study as important limitations were identified. Literature searches were not comprehensive enough to ensure that all relevant studies were identified, methods used to screen studies for inclusion and extract data of included studies were not rigorous. In addition, quality assessment of studies was not conducted, therefore it is not clear which studies were subject to low or high risk of bias.