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Auzita Sajjadi, Lisa A Ostrin; Objective Measurement of Light Exposure and Eye Growth in Children over One Year. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2490.
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© 2017 Association for Research in Vision and Ophthalmology.
The amount of time spent outdoors has been linked to the development and progression of myopia in children. Objective measurements of light and activity can more accurately quantify risk factors for myopia. In this longitudinal study, a wrist-worn device was employed to continuously measure activity level and light exposure to determine the influence of light levels on eye growth in young children.
School-aged children (5-10 yrs, n=64), wore an actigraph device (Actiwatch Spectrum) continuously for up to five 2 week sessions (during both school and summer time) to quantify activity levels, sleep, and ambient light exposure. Comprehensive eye examinations including cycloplegic refraction and axial length (AL) measurements were given at the start of the study and at one year. Additionally, parents filled out an activity questionnaire. Actigraph data were analyzed in terms of the season and correlated to changes in spherical equivalent refraction (SER) and (AL) over one year.
Subject age at enrollment was 7.55±1.8 yrs. Baseline SER was +0.87±1.38D and axial length was 22.6±0.84mm. At one year, SER significantly decreased to +0.63±1.65D and AL increased to 22.82±0.91mm. Children spent an average of 1:22±0:33 hr:min outdoors during school and 1:55±0:46 outdoors during summer months. Daily light exposure was significantly greatest in the summer, while there was no change in activity or sleep between seasons. Regression analysis showed a trend for greater AL increase with decreased cumulative light exposure and blue light exposure. However these failed to reach significance (p=0.11 and 0.19, respectively). Myopes spent an average of 16 additional minutes outdoors compared to emmetropes, but this, as well, did not reach significance (p=0.41).
Children spent significantly more time outdoors and received the highest light dose during the summer. With this small sample size, we failed to find a significant relationship between light exposure and eye growth despite the trend for greater light exposure and slower axial length increase. Further analysis of the spectral composition and illumination levels with a larger sample size may serve to provide recommendations for the ideal amount of time for children to spend outdoors in regards to eye growth.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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