The Association between Near Work Activities and Myopia in Children—A Systematic Review and Meta-Analysis

Methodological quality of the review: Medium confidence

Author: Hsiu-Mei Huang, Dolly Shuo-Teh Chang, Pei-Chang Wu

Region: Asia, North America, Australia, Europe

Sector: Myopia

Subsector: Myopia risk factor (near work activities)

Equity focus: No

Study population: Children

Type of programme: Community and school based

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: The prevalence of myopia has increased dramatically in recent years around the world and, in some highly educated groups, such as law and medical students, it now exceeds 80 per cent. Consistent with the increase in overall myopia, there has been an increase in the prevalence of high myopia. Therefore, it is important to identify the possible risk and preventive factors in the development of myopia. Near work is considered as the activities done at short working distance, such as reading, studying (doing homework, writing), computer use/playing video games, or watching TV, etc.) However, the associations between time spent reading and myopia have not been consistently observed.

Objectives: The objective of this review was to examine the magnitude of the association between time spent on near work and myopia, by systematically identifying and quantitatively combining all available and relevant studies.

Main findings: A total of 15 cross-sectional studies met the criteria for inclusion in this meta-analysis. All studies were published between 1989 and 2014, and included a total study population of 25,025 individuals. Time spent on near work was assessed by questionnaires completed by parents, children or both. The definition of myopia varied across studies. Among 1,005 7-9-year-old children from the Singapore Cohort Study of the Risk Factors for Myopia (SCORM), those who read more than two books per week had a higher risk (OR=3.05; 95% CI=1.80-5.18) of having myopia (spherical equivalent error (SER) of at least ≦- 3.0 diopters [D]) than those who read fewer than two books. The results show that more time spent on near work activities was associated with higher odds of myopia (odds ratio [OR]=1.14; 95% confidence interval [CI] =1.08-1.20) and that the odds of myopia increased by 2% (OR:1.02; 95% CI=1.01-1.03) for everyone diopter-hour (hr) more of near work per week.

Methodology: Authors’ inclusion criteria was based on studies that reported any near work activities as covariates with myopia, myopia incidence or progression as the outcome measure. The search was done on several databases (Medline, Embase, and the Cochrane Library), from 1 April 1989 to 1 May 2014, to identify potentially relevant articles. Our search included combined Medical Subject Headings and keywords for children with myopia (study population) and near work activities. There were no language restrictions. After deleting duplicate articles, two authors independently screened the studies for inclusion, retrieved potentially relevant studies, and determined study eligibility. Then we reviewed the bibliographies of all selected articles to identify additional studies. Disagreements were resolved by consensus. Each article was rated according to the “strength of evidence”, as defined by the American Academy of Ophthalmology’s glaucoma panel. To evaluate the effect of near work on myopia, the evaluated outcomes included prevalent myopia, myopic development or progression. We reported dichotomous outcomes as odds ratios (ORs) and continuous outcomes as the mean and their respective 95% confidence intervals (CIs). The I² statistic was calculated to determine the proportion of inter-study variation due to heterogeneity, which suggested thresholds for low (25-49%), moderate (50-75%) and high (>75%) values. We assessed for possible publication bias or a systematic difference between smaller and larger studies with a funnel plot. All statistical analyses were performed with STATA/SE 12.0 (Stata-Corp LP, College Station, TX). A two-sided P value less than 0.05 was regarded as significant for all analyses.

Applicability/external validity: The authors reported that the number of available prospective studies is considerably low. A number of factors may contribute to the inconsistent conclusions; these factors include: differences in study design, children’s ethnicity, definitions of myopia and near work, accuracy of the self-reported or parent-reported activity times, and quality of the data collection. In addition, the impact of near work on myopia may be cumulative over time, and lighting or temporal factors (such as, break time between texts) may also affect final estimations.

Geographic focus: No studies from LMIC were included in this review, but near work activities and eye health is a global issue affecting both high income countries and LMIC.

Summary of quality assessment:

There is medium confidence in the conclusions about the effects of this study. Authors did not contact authors/experts as part of the search strategy, and did not conduct a search of unpublished literature. In addition, data extraction was done by one reviewer.