Objectively measured near work, outdoor exposure and myopia in children

Abstract

Aim: To reassess the association between near work, outdoor exposure and myopia in children through an objective approach.

Methods: Eighty-six children (10.13±0.48 years) were asked to wear Clouclip, a newly developed wearable device that is able to measure working distance and eye-level illuminance, for a complete week to obtain information on near work and outdoor exposure. The mean daily Clouclip wearing time was 11.72±1.14 hour. The spherical equivalent refraction was determined by cycloplegic autorefraction.

Results: The myopic children were found to be exposed to light intensities >3000 lux (0.68±0.50 hour vs 1.02±0.53 hour, p=0.012) and >5000 lux (0.42±0.35 hour vs 0.63±0.31 hour, p=0.004) for shorter durations on average each day than the non-myopic children. Additionally, the myopic children spent more time on average each day on activities at a distance of <20 cm than non-myopic children (1.89±0.61 hour vs 1.52±0.77 hour, p=0.019). In the multivariate logistic analysis, the time spent with a higher light intensity (>3000 lux (OR=0.27, 95% CI: 0.10 to 0.72, p=0.009); >5000 lux (OR=0.11, 95% CI: 0.02 to 0.56, p=0.008)) and a working distance of <20 cm (in a circumstance of >3000 lux (OR=1.17, 95% CI: 1.09 to 1.86, p=0.038) or in that of >5000 lux (OR=1.12, 95% CI: 1.03 to 1.77, p=0.046)) were the independent protective factors and risk factors, respectively.

Conclusion: The current study provides novel evidence, based on objective data, to support the association between the intensity of near work, light intensity and myopia. However, the causality and the dose-effect relationship need to be investigated further.

Keywords: epidemiology; optics and refraction.

Figure 1

The Clouclip device. Locations of the sensors in the Clouclip device (A) and Clouclip attached to the right arm of a spectacle frame (B).

Figure 2

Temporal patterns of light exposure (A) and near-work activities between the non-myopic and myopic children (B). The light exposure data was plotted on a log scale. Significantly different levels of light intensity experienced by the two groups were observed in the periods of 10:10 a.m.~10:30 a.m., 12:20 p.m.~14:10 p.m. and 16:00 p.m.~17:30 p.m. Significantly different levels of near-work distance were also noted in the periods of 10:10 a.m.~10:30 a.m., 12:30 p.m.~14:00 p.m. and 17:30 p.m.~20:00 p.m.