Modern electronic devices do not expose children to “unusually high levels” of hyperopic defocus, according to a recent study. If these devices are contributing to myopia, it may have more to do with the amount of time children spend looking at them up close and not, necessarily, the electronic nature of the devices themselves, according to the research.
Investigators evaluated the accommodative behaviors of 8 children with myopia and 11 children without myopia (ages 7 to 16) using an open-field autorefractor at target vergences from -0.25 D to -5.95 D. Each participant viewed stimuli on a mobile device, at distances of 96.8 cm, 29.8 cm and 16.8 cm, and an LCD computer monitor, from a distance of 400 cm.
The investigators evaluated the subjects using 4 varying test conditions: light levels (lights on or off), stimulus size (scaled or nonscaled), stimulus type (text or movie), and binocularity (binocular or monocular). The subjects were asked to focus on the center of the screens. Children without myopia were tested without refractive correction while the children with myopia wore aspheric soft contact lenses without spherical aberration. The researchers measured their spherical refractive state every 0.2 seconds over a test period of at least 8 seconds per stimulus condition.
The researchers found no evidence of accommodative lags in children with myopia viewing electronic devices that were larger than previously reported with other stimuli. They also noted that children without myopia generally experienced larger accommodative lags across all natural viewing conditions than the children with myopia, especially while they viewed the mobile device at 16.8 cm. At that distance, accommodative lags among the children without myopia were 1.31 D ± 0.32 D, while those with myopia had lags of 1.11 D ± 0.35 D (P =.01). This difference in accommodative lags “is inconsistent with the hypothesis that larger accommodative lags are a causal factor for myopia development,” the authors said.
“The accommodation stimulus/response plots for both nonmyopic and myopic children share typical characteristics with previously reported data from children and adults viewing more traditional (nondigital) targets, indicating that electronic displays do not generate larger accommodative lags than other stimuli,” the researchers concluded.
Limitations of this study that might have influenced results include that the children looked ahead, rather than down, at the screens, and only for about 1 minute before the data collection.2 The researchers also did not know the precise distance children typically place between themselves and electronic screens, as it varies among children.
1. Sah RP, Ramasubramanian V, Reed O, et al. Accommodative Behavior, Hyperopic Defocus, and Retinal Image Quality in Children Viewing Electronic Displays. Optom Vis Sci. 2020;97(8):628-640. doi:10.1097/OPX.0000000000001543.
2. Guan X, Fan G, Wu X, et al. Photographic Measurement of Head and Cervical Posture when Viewing Mobile Phone: A Pilot Study. Eur Spine J. 2015 Dec;24(12):2892-8. doi:10.1007/s00586-015-4143-3