A novel wearable sensor for objective measurement of distance and illumination.

Abstract

Purpose: To evaluate the rangefinding and light sensing capabilities of a novel wearable sensor, the Visual Environment Evaluation Tool (VEET) developed for myopia research.

Methods: The VEET 1.0 (Meta, LLC) is a temple-integrated system mounted on a spectacle frame. Both the left and right temples house four sensors each, angled straight ahead and 20° downward/4° nasal, respectively. For validation, VEET-mounted spectacles were placed on a mannequin head. An infrared camera was used to capture the spatial characteristics of the rangefinding beam. Distance measurements were collected against a wall for 5-400 cm. The accuracy of distance measurements for different target types, sizes and tilt was assessed. Ambient illumination was captured in different indoor and outdoor settings and compared to a lux meter.

Results: All devices (N = 20) were capable of capturing distances for the full range evaluated, 5-400 cm, against a wall. There was a strong relationship between the actual and measured distances, with a slope of 1.01 ± 0.003 and 0.95 ± 0.007, for the left and right temples, respectively. Distance measurements were repeatable across different target types, including paper and tablet. Mean beam diameter of five tested devices was 52.2° ± 7.5°. The VEET effectively measured distances across different target sizes, ranging from 2 × 2 cm and larger and target tilt ±60°. Illumination measurements across different indoor and outdoor settings demonstrated a strong linear relationship with lux meter readings (R² = 0.99 and 0.78 for the left and right temples, respectively), effectively distinguishing indoor (<1000 lux) and outdoor (≥1000 lux) illumination levels.

Conclusion: The VEET provides accurate quantification of real-time distances across different target types and sizes and is capable of effectively distinguishing indoor and outdoor illumination levels. The VEET will be valuable in studies evaluating risk factors for myopia to gain a better understanding of the role of near work and light exposure.