Abstract
Purpose :
The increased availability of light sensing wearable technologies has made it possible to objectively characterize a child’s habitual indoor and outdoor behaviors towards a better understanding of the environmental risk factors associated with myopia. Key factors of interests are the light levels entering the eye and the dynamics of a child’s outdoor and indoor activity. Devices designed to be worn on the wrist, around the neck or spectacle mounted are now available. However, while there are hints that body position affects the output of such devices, there has been no direct study. The aim of this study was to assess the effect of body location on the output of 2 commonly used light sensing wearable technologies.
Methods :
Young adult subjects (n=5) wore each of two light sensing wearable technologies: Actiwatch Spectrum Pro (Phillips Respironics) and HOBO light pendant (Onset), both of which have seen application in human myopia-related studies. They were simultaneously mounted at several body positions (wrist, bicep, neck, head) while performing everyday tasks (walking outdoors & indoors, working on a laptop, using a mobile phone, reading a book) for 5 min each (measurements taken at 30 sec epochs). Prior to data analysis, each device was calibrated against a known light source with a photometer, which was also used to collect additional data during field testing with measures being made at eye level every 30 sec. For each of the tasks, illuminance levels were calculated from outputs of each device, averaged across the 5 min of recording, and comparisons made across both devices and body position.
Results :
There was tremendous variation with body position in recorded illuminance levels during some tasks. When walking outdoors, wrist-mounted devices yielded much lower illuminance levels compared to other body positions (~ 60% dimmer). When using a laptop, over 100% variation in illuminance levels across body position was observed for some subjects, with large inter-subject variability, likely reflecting the variation in arm movements across individuals.
Conclusions :
The placement of light-sensing wearable technologies is a critical determinant of their output. Data from our study argue for a more standardized approach to their use in studies aimed at understanding myopiagenic risk factors, for example, mounting at the head level to best quantify habitual visual environments, including during outdoor activities.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.