Greater daily digital screen exposure was associated with higher odds of myopia in a systematic review and dose-response meta-analysis published in JAMA Network Open, although the researchers cautioned that the evidence was observational, highly heterogeneous, and insufficient to establish causality.
The analysis included 45 studies involving 335,524 participants with a mean age of 9 years. Researchers searched PubMed, Embase, the Cochrane Library, CINAHL, and ClinicalTrials.gov through November 25, 2024. Digital screen exposure included smartphones, tablets, game consoles, computers, and television.
In the linear dose-response analysis, each additional hour of daily screen exposure was associated with 21% higher odds of myopia. The analysis showed substantial heterogeneity across studies (I² = 99%), which the researchers said limited confidence in the pooled estimate.
In the nonlinear analysis, which included 34 studies involving 314,910 participants, 1 hour of daily screen exposure was associated with 5% higher odds of myopia, while 4 hours was associated with nearly double the odds compared with no exposure. The dose-response curve suggested that odds began increasing statistically significantly beyond 1 hour of daily screen exposure, rose most sharply between 1 and 4 hours, and then increased more gradually beyond 4 hours.
The researchers described the findings as suggesting “a potential safe range of 1 hour of daily screen exposure,” but they also cautioned that the estimate applied specifically to screen exposure independent of other near-work activities such as reading and writing. They noted that cumulative near-work exposure likely contributes to myopia risk overall.
Screen exposure was associated with higher odds of prevalent myopia and myopia progression, but the association with incident myopia was not statistically significant. The researchers noted that the null finding for incident myopia may reflect the limitations of the available longitudinal data and raises the possibility of reverse causality, in which patients with myopia may spend more time using screens rather than screen exposure directly contributing to new-onset myopia.
Subgroup analyses showed statistically significant associations across age groups, study designs, and geographic regions. The strongest association by age was observed among children aged 2 to 7 years, in whom each additional hour of daily screen exposure was associated with 42% higher odds of myopia. Corresponding odds increases were 12% among patients aged 8 to 18 years and 16% among adults aged 19 years and older.
Most included studies were conducted in Asian populations, where myopia prevalence was already high prior to widespread digital device adoption. The researchers noted that this may limit the generalizability of the dose-response findings to other populations and suggests that screen exposure represents only one component of broader environmental and behavioral risk factors for myopia.
Studies evaluating combined device exposure showed stronger associations than those evaluating single devices alone. However, the researchers cautioned that the finding may partly reflect underreporting of total screen exposure when multiple devices are used rather than a true interaction effect between device types.
The researchers emphasized that reduced outdoor exposure may be an important confounder because screen use often occurs indoors. They noted that evidence supporting outdoor time as protective against myopia is stronger than the evidence linking screen exposure directly to myopia risk and suggested that strategies aimed at increasing outdoor activity and reducing overall near-work exposure may be more clinically meaningful than focusing solely on screen limits.
Additional limitations included variability in myopia definitions and screen exposure measurements across studies. Twelve studies relied on self-reported myopia, and adjusted estimates were used when available but unadjusted estimates were included when adjusted data were unavailable. Most included studies were cross-sectional, limiting conclusions regarding temporality and causation. The overall certainty of evidence was rated as low.
The findings “could offer meaningful insights for future research and inform educational strategies and public health policies aimed at addressing the myopia pandemic,” wrote Ahnul Ha, MD, of Jeju National University Hospital and Jeju National University School of Medicine, and colleagues. The researchers noted that global projections estimate that nearly one-half of the world’s population may have myopia by 2050.
Disclosures: The researchers reported no conflicts of interest. The study was supported by a 2024 scientific promotion program funded by Jeju National University.
Source: JAMA Network Open
