The prevalence of myopia and use of electronic displays by children has grown rapidly in recent years. We found that children viewing electronic displays, however, experience hyperopic defocus levels similar to those previously reported for other stimuli.
This study aimed to compare accommodative behavior of nonmyopic and myopic children viewing a computer screen or mobile phone.
Accommodative behavior was examined in 11 nonmyopic and 8 myopic children (11.32 ± 2.90 and 14.13 ± 2.30 years, respectively; P = .04; refractions, +0.51 ± 0.51 and −2.54 ± 1.29, respectively) using an open-field autorefractor (Grand Seiko) at target vergences from −0.25 to −5.95 D. Different size (scaled or nonscaled) and type (text or movie) stimuli were presented on an LCD monitor (distant) or an iPhone (near), with subjects viewing monocularly or binocularly in an illuminated or dark room.
At the typical reading distances (16.8 and 29.8 cm), all 19 children exhibited some amount of accommodative lag. Stimulus type had little impact on accommodation. However, slightly but statistically significant lower slopes were observed (Bonferroni-corrected significance level of P ≤ .01) for low room lighting (0.80 vs. 0.76; t test, t = 3.88; P = .003), nonscaled targets (0.83 vs. 0.77; t test, t = 4.28; P = .001), and monocular viewing (0.83 vs. 0.74; t test, t = 4.0; P = .002) in the nonmyopic group only. When viewing nonscaled stimuli binocularly (natural viewing), the means and standard deviations of accommodative lags (averaged across room lights on and off, and text and movie) were generally larger for the nonmyopes at all distances and were largest at 16.8 cm (1.31 ± 0.32 D for the nonmyopes and 1.11 ± 0.35 for the myopes; t test, t = 2.62; P = .01).
Generally small (mostly <1.00 D) amounts of hyperopic defocus are present in children binocularly viewing handheld electronic devices (nonmyopes slightly more than myopes). Modern electronic devices do not expose children to unusually high levels of hyperopic defocus.