Environmental and Behavioral Factors in Childhood Myopia

Purpose: Near work and light exposure are known risk factors for myopia. This dissertation validates the Clouclip, a rangefinding device, to assess its utility in measuring viewing distance and ambient illumination, and to use it along with an actigraph device and questionnaire to measure environmental and behavioral risk factors for myopia in four different studies. Methods: Study 1 validated the Clouclip for measuring distance and ambient light, and measured viewing behaviors during four near tasks in adults. Study 2 measured viewing behaviors in children during similar tasks as in study 1. Study 3 utilized the Clouclip and Actiwatch in participant’s habitual environment over a one week measurement period in adults. Study 4 used the Clouclip, Actiwatch, and a questionnaire to comprehensively quantify visual behaviors over one week in myopic and non-myopic schoolchildren. Results: Study 1) Clouclip measured distance and ambient light levels were comparable to actual values, and viewing distance in adults differed by type of near task but not by refraction. Study 2) Viewing distance and posture differed in children by type of near task 3) Clouclip- and Actiwatch-measured illumination were correlated, while questionnaire overestimated compared to objective sensors. Study 4) Objective measures showed that myopic children spent a greater amount of time on near + intermediate viewing and less time outdoors compared to non-myopic children. Questionnaire-derived electronic device use was 12.0 ± 0.7 hrs per day with no differences between refractive error groups.
Conclusion: Wearable objective sensors allowed precise quantification of behavioral components related to myopia. Findings demonstrate that several factors differ in the visual environment between myopic and non-myopic children.