Objectively measured near work, outdoor exposure and myopia in children

Br J Ophthalmol. 2020 Nov;104(11):1542-1547. doi: 10.1136/bjophthalmol-2019-315258. Epub 2020 Feb 19.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Child
  • Female
  • Humans
  • Leisure Activities*
  • Male
  • Myopia / physiopathology*
  • Radiometry / instrumentation
  • Reading
  • Refraction, Ocular / physiology
  • Sunlight*
  • Surveys and Questionnaires
  • Work / physiology*