2.4: Influence of Screen Devices using on Myopia in Children aged 7–11 years: a Multi‐center Experimental Study

Purpose. To investigate the working distances when children read text with different font sizes and watched videos under different learning facilities by various devices. Methods . There were two experiments in this study. In Experiment 1, 35 children (8.97 ± 1.12 years old, 10 females) with normal or corrected‐to‐normal visual acuity (≤ 0.00 logMAR) were recruited. Subjects were asked to read a fairy tale that was shown in five different font sizes (tablet, laptop, digital book, printed book: 9, 10.5, 12, 14, and 16 pounds; cellphone: 12, 14, 16, 18, and 20 pounds) by a tablet, laptop, cellphone, digital and printed books. In Experiment 2, 10 children (8.3 ± 1.16 years old, 3 females) were asked to watch videos (online education program) using a tablet, laptop and cellphone. Throughout the experiments, Clouclip, which is a wearable and continuous rangefinder, was used to measure the working distances (the distance between the eyes of the observers and the screen). Results. In Experiment 1, the mean working distance was significantly different amongst different devices (tablet: 43.8 ± 1.8 cm; laptop: 50.4 ± 1.8 cm; cellphone: 31.8 ± 1.2 cm; digital book: 28.9 ± 1.2 cm; printed book: 37.4 ± 1.7 cm; P < 0.001). The working distance increased with larger font sizes (P < 0.001). The working distances exceeded 30 cm when children read the tale with the tablet, laptop and printed book at all font size conditions. However, the working distances were less than 30 cm when children read the tale using a digital book at all font size conditions, using cellphone under 14 pounds. In Experiment 2, the working distance was significantly different amongst different screen devices (tablet: 49.5 ± 1.8 cm; laptop: 60.6 ± 5.7 cm; cellphone: 45.3 ± 3.4 cm; P = 0.018). The working distance slightly increased within 25 minutes after subjects started watching the videos but decreased after 25 minutes of the viewing session; they were all larger than 30 cm by all screen devices. Conclusions. Children demonstrated different working distances when they read and watched video in different conditions. Closer working distances were found when the subjects used smaller screen devices with a smaller font size compared to those when the subjects used larger screen devices with a larger font size during reading; this might be a risk factor for myopia progression. Larger distances were observed in the laptop compared with that in the tablet and the cellphone when children watched videos. We also recommend that a session of watching a video to not exceed 25 minutes. Our work provides an insight about controlling for myopia by informing the working distance of children when they use various screen devices.