The distance at which a child views content on a mobile phone may have an effect on their risk for developing myopia over time, according to a speaker at the virtual Association for Research in Vision and Ophthalmology meeting.
“Children using mobile electronic devices employ nearer viewing distances than those often reported in adults, which would make them prone to myopia due to chronic hyperopic defocus,” Renfeng Xu, MD, PhD, said.
Two hypotheses for the cause of myopia include high near work, such as reading a book or looking at a cell phone, and lower levels of retinal illuminance associated with the indoor environment. These two factors can typically co-occur in children engaging in near-viewing activities, Xu said.
Xu and colleagues used real-time monitoring technology to directly quantify environmental light levels and the viewing behaviors of children. The researchers used the VisionApp commercial software to determine the average viewing distances of 20 children using a mobile phone for five different tasks with varying degrees of environmental light.
Children watched a movie with room lights on, watched a movie with lights off, read small text of 8-point type at 1 m, read large text of 16-point type at 2 m and played a video game, all in a random sequence. The app recorded viewing distances continuously for 5 minutes at a sample rate of 15 frames per second, and average distances were reported once per second, Xu said.
The viewing distance remained stable for all the tasks over the 5-minute period, with a mean viewing distance of 24 cm reported across all subjects. This decreased to 21 cm when children read the small-sized text, which might potentially entail the highest risk for near-work-related myopia development, Xu said.
“The mean viewing distance for adults was between 40 cm to 50 cm. The viewing distances for children are significantly smaller than that for adults,” she said.
Further research on viewing behavior is necessary to investigate the differences between Asians and Caucasians, and myopes and emmetropes, both with and without myopia treatment, she said. – by Robert Linnehan
Xu R, et al. Viewing behavior of children using mobile phones. Presented at: Association for Research in Vision and Ophthalmology meeting; May 6, 2020 (virtual meeting).
Disclosure: Xu reports no relevant financial disclosures.