JMIR Publications

ABSTRACT

Background:

In recent years, the global prevalence of myopia among children has continued to rise. The preschool years represent a critical period for visual development, and the widespread adoption of electronic screens among young children has brought increasing attention to pediatric visual health. However, the association between visual environmental exposures related to screen use and the risk of myopia in preschool children has not been thoroughly investigated.

Objective:

This monitoring study aimed to examine the relationship between electronic screen brightness, ambient illuminance, and axial length in preschool children, providing scientific evidence for myopia prevention and control in early childhood.

Methods:

This cross-sectional monitoring study was conducted between March and July 2023 in Shanghai, China, involving two representative samples of kindergarten children aged 3 to 6 years. Each participant was provided with a tablet pre-installed with intelligent monitoring software, which continuously and objectively recorded real-time data on screen time and screen brightness over a consecutive seven-day period. In addition, comprehensive data collection encompassed standardized ophthalmic assessments, high-precision ambient illuminance measurements, simulated laboratory lighting evaluations, and parental questionnaires. Associations between ambient illuminance, screen brightness, and axial length were analyzed using multivariable linear regression and restricted cubic spline models.

Results:

Of the 199 children included in the total sample, 124 were boys (62.3%), and 75 were girls (37.3%). After adjustment for demographic characteristics, parental myopia, and screen use behaviors, the median ambient illuminance during tablet use was significantly inversely associated with axial length (β= -0.13, 95% CI: -0.22 to -0.04, P = 0.006). Restricted cubic spline analyses revealed a nonlinear dose–response relationship between median screen brightness during tablet use and axial length （Pnon-linearity=0.004）.

Conclusions:

Enhancing ambient lighting to appropriate levels during electronic device use may effectively mitigate abnormal axial elongation and thus reduce the risk of myopia in children. Both ambient illumination and screen brightness are critical determinants of ocular development in preschoolers. Optimizing environmental lighting and digital device settings can help safeguard children’s visual health and inform guidelines for safe digital device use.