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M. Tarver–Carr, R. Wojciechowski, D. Grover, N. Congdon; Validation of an Instrument to Measure Near Work . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5612.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: : There are many suspected associations between the amount of near work performed early in life and the development of myopia. We proposed to develop and validate an instrument to measure near work during childhood. Methods: We empirically determined a number of activities that participants of different current ages might have performed during their childhood and early adult years, quantifying the amount of time spent on each. The instrument consisted of fifteen items assessing the hours devoted to the following activities per week between the ages of 5 to 10, 11 to 17, and 18 to 21: recreational reading, school work, outdoor activities, playing games requiring up–close work, and watching television. The interviewer–administered questionnaire was validated using a pilot sample of 84 clinic and population–based subjects. Results: The mean age of the subjects was 57 (range 9 to 84) years, with 58 percent being men, 61 percent being Caucasian, and 62 percent having completed high school. The reliability or internal consistency of the instrument measured by the Cronbach’s alpha was 0.865. When the data were stratified by the age group in which the near work was performed, the alphas ranged from 0.55 to 0.73, with the highest reliability being in the oldest age group (18–21 years). Factor analysis, performed with the principal components extraction method, was used to establish internal validity of the instrument. This technique produced one underlying factor defined as near work for which every item had high loadings and which explained over 35% of the variance. This factor was robust when stratified by age, sex, and race. Further analyses limited to those with at least a high school degree produced similar results. Conclusions: This pilot study suggests that the near work instrument is both reliable and shows internal validity. Previous studies of myopia risk have tended to ignore the important component of leisure–associated near work.
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