Visual fatigue is associated with improper viewing angle, height, and distance during online learning in children, according to research published in Healthcare. Researchers designed a vision protective device based on these findings. 

The researchers recruited 52 children (aged 9.4±0.6 years, 50% girls) from a single center between September 2021 and January 2022 to participate in the study. They instructed participants to fast from reading and using electronic devices for 1 hour before initiating the investigation. 

The team fitted the children with head-mounted eye-tracking devices and measured participants’ sitting height, eye height, and corrected-to-normal vision. They provided an adjustable stand to allow participants to adjust the tablet’s angle, height, and distance based on their viewing habits. The investigators then showed the children a 30-minute video and administered a test to determine their reading efficiency.


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Researchers subjectively assessed fatigue based on eye symptoms, headache symptoms, and body pain. They found that blink frequency (BF) decreased between 5 and 10 minutes of initiating the activity before it increased and peaked between 20 to 25 minutes (10.680±3.074, P =0.00). Visual fatigue appeared after 15 minutes of screen time (P =.011).

The team also noted that participants preferred a viewing angle of 21.86±2.22°, a mean viewing height of 198.56±12.08 mm, a viewing distance of 531.26±19.89 mm, and an angle of 81.87±3.39° between their line of sight and the screen. They used their calculations to develop a limited number of vision protective device trials. 

“Based on this method, a series of children’s visual protection products can be developed to control more influence factors of visual fatigue, and provide human–machine data, and innovative application reference for the design of auxiliary electronic equipment viewing products,” according to the researchers.

Limitations of the study include the strict inclusion of children from only 2 grade levels and a single center design.

Reference

Feng D, Lu C, Cai Q, Lu J. A study on the design of vision protection products based on children’s visual fatigue under online learning scenarios. Healthcare. Published online March 25, 2022. doi:10.3390/healthcare10040621