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Majid MOAFA, Amanda French, Robert Heard, Kathryn Ailsa Rose; Development of myopia among adolescents: a validation of instrument study. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2937.
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© ARVO (1962-2015); The Authors (2016-present)
To validate data collected on time spent outdoors using the WHO Refractive Error in School Children questionnaire compared to a diary of daily activities and objective measures of light exposure using a light data logger (LDL)
The questionnaire was filled out by 100 university students (aged 18 to 50 years) describing their pattern of indoor and outdoor activity on a typical week and weekend day. For the next four days (2 week and 2 weekend days) they wore a HOBO LDL (model UA-002-64, Onset Computer Corporation) on their upper arm while documenting in a diary time spent in activities and whether indoors or outdoors. They then attend a short focus group to discuss the ease of use and perceived accuracy for each instrument. This study adhered to the tenants of the Declaration of Helsinki
Comparison of the measures of indoor and outdoor time recorded using the diary versus the LDL were similar with both instruments recording close to 11 hours spent indoors and 1 hour outdoors on a weekday and weekend day. The LDL and diary were highly correlated for indoor time on both weekdays and weekend days with Intraclass Correlation (ICC) = 0.894 and 0.885 respectively (both p < 0.001). For time outdoors, correlations were significant but not as strong; ICC = 0.256 (p = 0.005) for weekdays, and ICC = 0.332 (p < 0.001) for weekend days. Agreement between the LDL and questionnaire, however, was poor for indoor and outdoor time estimates, on both weekdays and weekend days, with ICCs ranging from -0.078 to 0.262.<br /> The outdoor time measured by questionnaire during weekdays was on average 0.94 hours more than LDL (p<.0001) and indoors also was on average 1.33 hours more (p=0.001). On weekend days participants overestimated time outdoors by 2.71 hours per day (p<.0001), however, indoor time was underestimated by 2.88 hours (p<.0001). Participants reported that the LDL and questionnaire were easy to use while the diary was burdensome
While LDLs are objective and reliable, their cost may preclude use in large-scale studies. Questionnaires have been widely used to establish the link between time outdoors and myopia, in this study, participants commonly overestimated time spent outdoors. The greater correlation between the diary and LDL data suggests an alternative questionnaire design based on a 24 hour clock may elicit more accurate assessment of hours spent outdoors
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