Continuous smartphone use raises myopia risk in teens

Adolescents spend about 4 hours per day on their smartphones, and episodes of 20 minutes continuous use appear to lead to more myopic refractive errors, especially among those with low outdoor exposure, a study reports.

Using a mobile application, researchers examined axial length and refractive error of the eyes of 525 adolescents (mean age 13.7 years, 54 percent girls) in relation to their smartphone use. The app was designed to measure smartphone use, gauge face-to-screen distance, and pose questions about outdoor exposure.

All participants underwent cycloplegic refractive error and ocular biometry assessments. Mean daily smartphone use was quantified as hours per day, with continuous use defined as the number of 20-minute episodes of screen viewing without breaks.

Myopia had a prevalence rate of 18.9 percent. During schooldays, the children spent an average of 3.71 hours per day on their smartphone. There was a trend of association between total smartphone use and the ratio of axial length and corneal radius (AL/CR; β, 0.008, 95 percent confidence interval [CI], –0.001 to 0.017) but not spherical equivalent (SER).

On average, the children had 6.42 episodes per day of continuous smartphone use. These episodes significantly correlated with both SER (β, –0.07, 95 percent CI, –0.13 to –0.01) and AL/CR (β, 0.004, 95 percent CI, 0.001–0.008).

In an analysis that stratified for outdoor exposure, the associations between continuous smartphone use and SER and AL/CR were seen only among teenagers with limited exposure (β, –0.10, 95 percent CI, –0.20 to –0.01 and β, 0.007, 95 percent CI, 0.001–0.013, respectively).

Meanwhile, smartphone use during weekends showed no significant association with SER and AL/CR, nor did face-to-screen distance.

The findings highlight the importance of taking frequent breaks when using a smartphone, particularly among teenagers. Future large longitudinal studies are needed to further explore safe screen use in youth.