Impact of various types of near work and time spent outdoors at different times of day on visual acuity and refractive error among Chinese school-going children

Abstract

Background Various types of near work have been suggested to promote the incidence and progression of myopia, while outdoor activity appears to prevent or retard myopia. However, there is a lack of consensus on how to interpret these results and translate them into effective intervention strategies. This study examined the association between visual acuity and time allocated to various activities among school-going children. Methods Population-based survey of 19,934 students in grade 4 and 5 from 252 randomly selected rural primary schools in Northwest China in September 2012. This survey measured visual acuity and collected self-reported data on time spent outdoors and time spent doing various types of near activities. Results Prolonged (>60 minutes/day) computer usage (-0.025 LogMAR units, P = .011) and smartphone usage (-0.041 LogMAR units, P = .001) were significantly associated with greater refractive error, while television viewing and after-school study were not. For time spent outdoors, only time around midday was significantly associated with better uncorrected visual acuity. Compared to children who reported no midday time outdoors, those who spent time outdoors at midday for 31–60 minutes or more than 60 minutes had better uncorrected visual acuity by 0.016 LogMAR units (P = .014) and 0.016 units (P = .042), respectively. Conclusions Use of smart phones and computers were associated with declines in children’s vision, while television viewing was not. Statistically significant associations between outdoor time at midday and reduced myopia may support the hypothesis that light intensity plays a role in the protective effects of outdoor time.

The association between digital screen time and myopia: A systematic review

“…Although we found no significant association between screen time and myopia in the meta‐analysis, these results are not convincing evidence of the link between digital devices and myopia, due to the low number of studies included. In the review results we found that the more recent studies seem to show a trend of association that might be related with the increase in screen time for the more recent years. However, this is expected given the introduction and rise in screen time in children, and this trend should be critically evaluated as educational near work may now be primarily screen time in origin instead of traditional "paper and pen” with a substitution effect.…”

“…The majority of the studies included in this review published in 2014 and above show positive associations (five out of seven studies; Figure ). Positive associations where reported in children (aged 5–16 years) from Vietnam in 2014, India in 2015 and 2017 and China in 2016 and 2019 …”

Correlation of Myopia with Physical Exercise and Sleep Habits among Suburban Adolescents

“…Having at least 60 minutes of daily exercise [ 23 ] or one additional hour of outdoor time per week [ 26 ] could reduce the odds of a child having myopia. In addition, children who spent time outdoors at mid-day for 31–60 minutes or more than 60 minutes had better uncorrected visual acuity than students who spent less time outdoors [ 27 ]. However, other studies found that outdoor activities had less of a protective effect on myopia [ 6 , 28 ].…”

Positive mother‐child interactions and parenting styles were associated with lower screen time in early childhood

“…function, 9 sleep, 2 typical behaviours, 5,10 play, 11 the way they interact with their mothers 7,8,[12][13][14] and possibly their vision. 15 Parenting styles, caregiving behaviours and mother-child interactions have been demonstrated to influence children's screen time, especially background media exposure. [16][17][18] This paper refers to three types of parenting styles.…”