Research Review

Prevalence and Risk Factors of Myopia

August 16, 2021

By Dwight Akerman, OD, MBA, FAAO, FBCLA

Researchers from Finland investigated the correlations of near work, outdoor time, and parental myopia with the prevalence of myopia, which was defined as poor uncorrected distance vision, among schoolchildren of different ages, and the mutual impacts of these factors on the prevalence of myopia by reanalyzing data collected by a questionnaire for a study conducted in 1983 in Central Finland (Pärssinen 1986). 

Schoolchildren (n = 4,961) from the 1st, 5th, and 8th grades of school (7-, 11-, and 15-year-olds) in Central Finland were screened for vision followed by a questionnaire, which 4,352 (87.7%) candidates returned. Myopia prevalence was 3%, 15%, and 27% among 7-, 11-, and 15-year-olds, respectively, and if daily near work at home was ≤ 1 hr., myopia prevalence was 0.5%, 3.3%, and 17.6%, respectively. 

Myopic parents, more near work time, less outdoor time, a higher near work/outdoors ratio, and being a girl increased myopia risk. Myopia was uncommon in 7- and 11-year-olds whose daily near work at home did not exceed one hour or whose near work/outdoors ratio did not exceed 0.5. 

Additional time spent outdoors decreased the prevalence of myopia irrespective of the amount of near work time. Thus, to prevent myopia, it can be recommended that an equivalent increase in outdoor time should accompany any increase in near work time.

Abstract

Associations of near work time, watching TV, outdoors time, and parents’ myopia with myopia among schoolchildren based on 38-year-old historical data

Olavi Pärssinen, Markku Kauppinen 

Purpose: To study the prevalence and risk factors of myopia with data from a questionnaire study conducted in 1983 among Finnish schoolchildren.

Methods: Schoolchildren (n = 4,961) from the 1st, 5th, and 8th grades of school (7-, 11-, and 15-year-olds) in Central Finland were screened for vision followed by a questionnaire, which was returned by 4,352 (87.7%) participants. Myopia was categorized based on the questionnaire. Items concerned daily time spent on near work and outdoor activities, excluding time spent at school, watching TV, and parental myopia and the associations of myopia with these factors.

Results: The prevalence of myopia was 3%, 15%, and 27% among the 7-, 11-, and 15-year-olds, and if daily near work at home was ≤1 hr., myopia prevalence was 0.5%, 3.3%, and 17.6%, respectively. The adjusted risk of myopia for each daily near work hour was OR 1.476 (95% confidence interval 1.099-1.984, p = 0.010), OR 1.346 (1.170-1.584, p < 0.001), and OR 1.206 (1.076-1.352, p = 0.001), in the 3 age groups, respectively. The adjusted risk of myopia for each daily hour spent outdoors was OR 0.764 (0.648-0.900, p = 0.001) in the 11-year-olds and OR (0.840, 0.743-0.950, p = 0.005) in the 15-year-olds. Outdoors time prevented myopia at different levels of near work, although less at the highest levels, and near work increased risk of myopia with the level of outdoors time. If the ratio between near work and outdoors time was ≤0. 5 or >1.5, the prevalence of myopia was 1.4% versus 5.6%, 6.3% versus 24.7%, and 15.9% versus 36.9%, among the 7-, 11-, and 15-year-olds, respectively. The higher prevalence of myopia among the 11- and 15-year-old girls than boys was explained by more near work and less outdoor time among the girls. Having two myopic parents roughly doubled the risk of myopia compared to one myopic parent in the 11- and 15-year-olds.

Conclusions: Myopic parents, greater near work time, less outdoors time, a higher near work/outdoors ratio, and being a girl increased the risk of myopia. Myopia was rare in the 7- and 11-year-olds if daily near work at home did not exceed one hour or if the near work/outdoors ratio was not higher than 0.5. Outdoors time was associated with the prevalence of myopia at all levels of near work, although the association was weaker at the highest level.

Pärssinen, O., & Kauppinen, M. (2021). Associations of near work time, watching TV, outdoors time, and parents’ myopia with myopia among schoolchildren based on 38‐year‐old historical data. Acta Ophthalmologica.

DOI: 10.1111/aos.14980 

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