Screen use among children has been steadily increasing, and stay-at-home orders and virtual schooling have also boosted screen time. With a looming myopic epidemic, researchers are more concerned than ever about the accommodative behavior of nonmyopic and myopic children when using electronic devices. However, a new study provides a glimmer of good news: viewing electronic displays doesn’t seem to cause any more hyperopic defocus than the defocus caused by other stimuli.
The researchers examined 11 non-myopic children and eight myopic children between the ages of eight and 16 with an open-field autorefractor at target vergences from -0.25D to -5D. The subjects viewed various stimuli on LCD computer monitors (distance) or on an iPhone (near) monocularly and binocularly in an illuminated or darkened room. At typical reading distances, 20cm and 33cm, all children demonstrated some accommodative lag. The researchers found that the type of stimulus had little effect on accommodation.
Statistically significant lower slopes were observed for low room lighting, non-scaled targets and monocular viewing in only the non-myopic group. Also in the non-myopic group, the means and standard deviations of accommodative lags were generally larger at all distances when viewing non-scaled stimuli binocularly (natural viewing), and were largest at 33cm.
“Modern electronic devices do not expose children to unusually high levels of hyperopic defocus,” the researchers noted. They found that generally small (≤0.5D) amounts of hyperopic defocus are present in children viewing a handheld electronic device binocularly, with non-myopes exhibiting slightly more than myopes.
Sah RP, Ramasubramanian V, Reed O, et al. Accomodative behavior, hyperopic defocus and retinal image quality in children viewing electronic displays. Optom Vis Sci. July 30, 2020. [Epub ahead of print].