Wearable Light Tracker Accurately Quantifies Light Exposure in Real Time

A wearable, clip-on, light-tracking device demonstrated repeatability and high correlation with a factory-calibrated device for tracking light exposure, according to research published in Ophthalmic & Physiological Optics.

The novel device records ambient light as a function of illuminance in real time using a complementary metal oxide semiconductor. It measures 47x37x16.4 mm in size, weighs 50 g, measures a 0 to 88,000 lux range of luminance, and has a battery life of 7 days at a sampling rate of 60 s/data.

Researchers performed a 2-phase investigation. During phase 1, the device was tested under 3 conditions including a controlled environmental setup, outdoors, and indoors. The team used 4 clip-on devices during this phase and tested their agreement with a lux meter. Phase 2 assessment involved dispensing the trackers to 21 adults and 8 children and recording light exposure over a 5 hour period. Participants logged their movement between indoor activities in an ‘activity diary’ and these movements were corroborated with data provided by the tracker.   

Intra-test and inter-device validation tests revealed high correlations among the 4 trackers (interclass correlation [ICC] range, 0.90-1.00) with a low overall mean difference (MD) compared with the lux meter in the controlled (MD, 641 lux), outdoor (MD, 74 lux), and indoor (MD, -35 lux) conditions.

Among study participants, 14 reported using their devices outside and all reported using their devices inside during the 5 hours phase 2 duration. The trackers were able to differentiate between indoor and outdoor locations using a cutoff value of 1000 lux with a specificity of 97.8% and specificity of 99%, according to the report.

“There is a growing concern regarding the rising prevalence and incidence of juvenile myopia, and time spent outdoors is the safest and most cost-effective strategy to tackle this,” according to the researchers. “Several public health initiatives related to time spent outdoors have been described in the literature, where the use of a light tracker can play a crucial role in better understanding the pattern of light exposure, motivate children to be outdoors, and design future light-based therapies.”

Study limitations include a small sample size.