Smartphone Use Associated with Refractive Error in Teenagers: The Myopia App Study

Abstract

Purpose: To investigate the association between smartphone use and refractive error in teenagers using the Myopia app.

Design: Cross-sectional population-based study.

Participants: A total of 525 teenagers 12 to 16 years of age from 6 secondary schools and from the birth cohort study Generation R participated.

Methods: A smartphone application (Myopia app; Innovattic) was designed to measure smartphone use and face-to-screen distance objectively and to pose questions about outdoor exposure. Participants underwent cycloplegic refractive error and ocular biometry measurements. Mean daily smartphone use was calculated in hours per day and continuous use as the number of episodes of 20 minutes on screen without breaks. Linear mixed models were conducted with smartphone use, continuous use, and face-to-screen distance as determinants and spherical equivalent of refraction (SER) and axial length-to-corneal radius (AL:CR) ratio as outcome measures stratified by median outdoor exposure.

Main outcome measures: Spherical equivalent of refraction in diopters and AL:CR ratio.

Results: The teenagers on average were 13.7 ± 0.85 years of age, and myopia prevalence was 18.9%. During school days, total smartphone use on average was 3.71 ± 1.70 hours/day and was associated only borderline significantly with AL:CR ratio (β = 0.008; 95% confidence interval [CI], -0.001 to 0.017) and not with SER. Continuous use on average was 6.42 ± 4.36 episodes of 20-minute use without breaks per day and was associated significantly with SER and AL:CR ratio (β = -0.07 [95% CI, -0.13 to -0.01] and β = 0.004 [95% CI, 0.001-0.008], respectively). When stratifying for outdoor exposure, continuous use remained significant only for teenagers with low exposure (β = -0.10 [95% CI, -0.20 to -0.01] and β = 0.007 [95% CI, 0.001-0.013] for SER and AL:CR ratio, respectively). Smartphone use during weekends was not associated significantly with SER and AL:CR ratio, nor was face-to-screen distance.

Conclusions: Dutch teenagers spent almost 4 hours per day on their smartphones. Episodes of 20 minutes of continuous use were associated with more myopic refractive errors, particularly in those with low outdoor exposure. This study suggested that frequent breaks should become a recommendation for smartphone use in teenagers. Future large longitudinal studies will allow more detailed information on safe screen use in youth.

Keywords: Myopia; Outdoor exposure; Refractive error; Smartphone use; Teenagers.