Analysis of distance sensor measurements to understand the effect of the school environment on children’s visual behaviour and risk for myopia

Aim and Research Question(s)

The aim is to investigate a possible connection between the presence of myopia and the everyday behaviour in two different school systems and to point out a difference between the two student groups. Therefore, the research questions that will be answered through this work are as following: Is the average near work distance depending on the educational style (free project work versus traditional instruction) of schools that children are attending? Do children who are allowed to move freely during lessons have significant different work distances during a school lesson? Is there a particularly shorter working distance in myopic students in comparison with normal-sighted (emmetropic) students?

Background

As the prevalence of myopia (short-sightedness) increases [1], measurement methods and technical devices to survey the behavior of people with and without myopia are becoming increasingly important in addition to traditional questionnaires. A pilot study at a local and an international school in Hong Kong found that myopia prevalence among students at the international school was lower than at the local school, although parental myopia and high myopia prevalence was much higher [2]. This suggests that environmental factors related to the educational system have a major influence on myopia development. To quantify this hypothesis a comparison of the working distance in a subcohort of these two school systems was made.

Methods

This master thesis is based on the analysis of distance sensor data collected as part of a health project in 2018 and 2019 with a total of 55 students (28 from an international school and 27 from a local school in Hong Kong). The visual behavior was measured during 90 minutes of lessons in their classroom, each child wore a LIDAR distance sensor as part of wearable technology glasses. The resulting absolute distances were converted to inverse distances (1/working distance in meters).

Results and Discussion

The students in the local school had significantly higher mean dioptric visual distance (i.e., shorter working distance) in class than students in the international school (2.55±0.45 m-1 vs. 1.82±0.23 m-1; two-sample t-test, P <0.001). In the local school, emmetropic children had a slightly but significant larger dioptric distance than myopic children (2.81±0.53 m-1 vs. 2.39±0.32 m-1, two-sample t test, P=0.017). No statistically significant difference was found between emmetropic and myopic children in the international school (1.87±0.22 m-1 vs. 1.75±0.24 m-1; two-sample t-test, P=0.182).

Conclusion

The presence of the significant differences in the visual behavior between Hong Kong children based on LIDAR data, suggests that there may be variation between the two schools. However, it cannot be confirmed that the presence of myopia causes a significant change in the behavior of schoolchildren in both schools. Although the association between education and myopia is well established, not many studies have compared risk factors for myopia in children in different schools from the same geographic area. These results suggest that the educational system plays an important role in determining children's visual behavior and thus may be an environmental risk factor for the development of myopia.

References

[1] Pan, C.-W., Ramamurthy, D., & Saw, S.-M. (2012). Worldwide prevalence and risk factors for myopia: Prevalence and risk factors for myopia. Ophthalmic and Physiological Optics, 32(1), 3–16. https://doi.org/10.1111/j.1475- 1313.2011.00884.x
[2] Liang, Y., & Kee, C.-S. (2022a). Risk Factors for Myopia in 2 Hong Kong School Systems: A Pilot Study. Asia-Pacific Journal of Ophthalmology, 11(1), 19–26. https://doi.org/10.1097/APO.0000000000000486