Summary:
Rates of childhood myopia (short-sightedness) are increasing worldwide and are expected to affect almost half of the global population by 2050. Children are also developing myopia earlier in life, and it tends to progress more quickly and reach more severe levels. This trend is concerning because higher degrees of myopia increase the risk of future eye diseases such as macular degeneration, retinal detachment, and glaucoma. Environmental factors appear to be driving much of this rise, particularly screen-time and less time outdoors, two factors linked to myopia development. Previous research on whether digital screens contribute to myopia has produced mixed results. Some studies reported increased risk from smartphones and tablets, while others found associations only with devices like computers or televisions. To clarify these inconsistencies, this review expanded the evidence base and conducted a meta-analysis. Studies were included if they assessed screen use across devices including phones, tablets, computers, gaming consoles, or television, and reported on myopia diagnosis or progression. Across 45 studies involving more than 335,000 children, each additional hour of daily screen time was linked to a 21% increase in the odds of myopia. The risk rose steadily from one to four hours of daily exposure, with odds nearly doubling at four hours. Beyond this point the increase continued, but at a slower rate. These findings suggest that screen time contributes to myopia in a dose-dependent manner. The pattern of risk indicates that limiting daily exposure to under an hour may be a safer threshold for reducing the likelihood of developing myopia. This information may help guide clinical advice and future research into modifiable risk factors for childhood myopia.
Abstract:
Importance The association of digital screen time with myopia has been documented, but the dose-response association and safe exposure threshold remain unclear. Objective To evaluate the dose-response association of time spent on digital screens with myopia risk. Data Sources PubMed, EMBASE, Cochrane Library databases, CINAHL, and ClinicalTrials.gov were searched for full-length articles from peer-reviewed journals without restrictions on study design, publication date, or language from inception to November 25, 2024. Study Selection Primary research articles investigating the association of exposure to digital screen devices (ie, smartphones, tablets, game consoles, computers, or television) with myopia-related outcomes (ie, prevalent or incident myopia and the rate of myopia progression) were identified by reviewers. Data Extraction and Synthesis Two independent reviewers extracted data using a standardized procedure in accordance with the Meta-Analysis of Observational Studies in Epidemiology (MOOSE) and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines. A random-effects, dose-response meta-analysis (DRMA) was utilized to examine the pattern of the association of screen time with myopia. Main Outcome and Measures Increased odds of myopia per hour of daily screen time. Results In the linear DRMA of 45 studies with 335 524 participants (mean [SD] age, 9.3 [4.3] years), an additional hour of daily screen time was associated with higher odds of myopia (odds ratio [OR], 1.21; 95% CI, 1.13-1.30). The nonlinear DRMA of 34 studies with 314 910 participants also indicated higher odds of myopia with increasing screen time, ranging from 1 hour of daily exposure (OR, 1.05; 95% CI, 1.01-1.09) to 4 hours (OR, 1.97; 95% CI, 1.56-2.40). The dose-response curve showed myopia risk increasing significantly between 1 to 4 hours of daily screen time, and then rising more gradually after 4 hours. Conclusions and Relevance In this systematic review and DRMA, a daily 1-hour increment in digital screen time was associated with 21% higher odds of myopia and the dose-response pattern exhibited a sigmoidal shape, indicating a potential safety threshold of less than 1 hour per day of exposure, with an increase in odds up to 4 hours. These findings can offer guidance to clinicians and researchers regarding myopia risk.
Article Publication Date: 21/02/2025
DOI: 10.1001/jamanetworkopen.2024.60026
