Lack of activity destroys the good condition of every human being.
Plato
Physical activity is essential to the physical and mental development of children. Physical inactivity accounts for 9% of worldwide premature mortality. It also contributes to increased visual impairment in mid as well as higher prevalence of myopia (shortsightedness).
As such, lack of physical activity is regarded as one of the most pressing health concerns that affects policymakers and society globally. However, research has found that only one in five children and one in 10 adolescents engage in the recommended levels of physical activity for good health (60 minutes of moderate- to vigorous-intensity physical activity per day).
Our research at Technological University Dublin focuses on the association between visual function in children and their engagement in physical activities. The study sampled 1,626 school children from 37 urban/rural schools in Ireland, both from socioeconomically advantaged and disadvantaged areas.
All participants’ eyes were inspected during the course of the school day, and parents/guardians filled out extensive questionnaires on the physical activity of their dependants. It was discovered that active participants who regularly engaged in physical activities, including sports, had better vision (both near and far). Moreover, these participants had better 3D vision and were less likely to need spectacles.
One in ten participants reported no physical activity, which rose to one in three among visually impaired participants. The study linked sedentary living with visual impairment (inability to see half a standard eye chart in either eye), amblyopia (lazy eyes), and myopia (shortsightedness).
Socioeconomic status and parental education
Parental education and employment partly explained the study’s inequality in physical activity levels. Prior research has established that inactivity levels can carry between parents and children, concluding that parents wishing to modify the activity levels in their children may need to address their own activity levels.
In our research, parents with third-level education and those with second-level education were four times and three times more likely, respectively, to report their child as regularly active than those with first-level education.
In contrast, socioeconomically disadvantaged and ethnic minority participants were seven and eight times more likely to be inactive, respectively. Furthermore, lower parental educational levels and social class may also indirectly affect physical activity levels by reducing exposure to sports, co-participation, and transportation. The substantial sports kit and coaching costs are other socioeconomic factors potentially limiting sports participation.
Level of vision and sports
Olympic-level athletes in sports ranging from field and track to ice hockey, softball, soccer, and speedskating have superior levels of visual acuity. Visual acuity measures the ability to see fine detail. Our study found that participants who are regularly engaged in physical activities had excellent visual acuity. Moreover, active participants who regularly engage in sports had excellent stereoacuity (the threshold level of depth perception).
Stereoacuity enables us to judge the relative position of objects in a three-dimensional space, which is vital in dynamic sports involving a moving target, such as ball sports like table tennis and soccer, where players are required to carry out important timed depth estimations.
For example, children with amblyopia (a lazy eye) have poor or no stereoacuity and lower athletic competence, such as aiming and catching skills. Amblyopic children are also less likely to excel in some sporting activities, which tracks through to adulthood; amblyopic adults are more likely to avoid visually demanding sporting activities due to difficulties catching a ball and balancing.
In our study, amblyopic participants were nearly six times more likely to be sedentary than participants without amblyopia. Encouragingly, participants who underwent successful amblyopia treatment were five times more inclined to engage in regular physical activities than participants with amblyopia who had not been treated.
This finding is critical, as brain plasticity is enhanced by physical activity, and visual (homeostatic) plasticity can be boosted with physical exercise in amblyopic and non-amblyopic individuals. Our study, therefore, highlights the positive impact and importance of addressing amblyopia, primarily preventable visual impairment, before school onset, when treatment is more likely to succeed in supporting health in later life.
Shortsightedness
The prevalence of myopia (shortsightedness) is increasing globally, with half the world’s population estimated to be shortsighted by 2050. Our study found that the absence of clinically significant refractive error was strongly associated with regular physical activity and sports. Conversely, sedentary living led to a three fold increase in the odds of becoming myopic. Shortsighted 12 to 13 year-olds spend more time on screens, less time outdoors, and less time engaged in physical activities than 12 to 13 year-olds who do not need spectacles.
Therefore, it may be the time spent outdoors and less on screens, not the physical activity itself, which offers a protective effect against myopia. For example, not being indoors engaged in near screen activities may be just as important as being involved in outdoor physical activities. Longitudinal research employing objectively measured physical activity and light exposure is therefore recommended.
Visual impairment
Visually impaired participants were ten times more likely to be inactive, which is concerning, as physical inactivity is associated with increased susceptibility to metabolic diseases and reduced high-level brain processing and function.
The reported fitness levels for visually impaired children are poorer than those for sighted children. Understanding the hurdles and barriers to engaging in sports and physical activities that visually impaired children encounter is vital. Consequently, children with visual impairment are an important target group when designing interventions to increase inclusion in sports and other physical activities.
The takeaway
Children who regularly engage in physical activity and sports have better vision and stereoacuity, and are less likely to need spectacles. Amblyopia, visual impairment, and myopia have been associated with sedentary lifestyles. Socioeconomically disadvantaged individuals and ethnic minorities are particularly affected.
Although the relationship between visual function and physical activity engagement may be bidirectional; it is hard to identify whether physical inactivity results in reduced vision or reduced vision results in reduced physical activity engagement.
Nonetheless, engaging in physical activities and cutting down near-sedentary activities are adaptable lifestyle changes that may prevent visual impairment and refractive errors such as myopia. Eyecare clinicians should include an assessment of physical activity engagement in consultations, incorporate physical activity advice and plans in managing children’s eyecare, and assess the benefits during follow-ups.
Public health education programs on increasing physical activity and reducing sedentary lifestyles are vital for schoolchildren and families. While investment in promoting and prescribing physical activity for all children is critical, policymakers should ensure socioeconomically disadvantaged, ethnic minorities and visually impaired children are further supported to participate in physical activity. These health benefits will provide long-term benefits from childhood to adulthood, leading to greater independence and overall better quality of life.
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Journal reference
Harrington, S., Kearney, J., & O’Dwyer, V. (2022). Visual factors associated with physical activity in schoolchildren. Clinical and Experimental Optometry, 1–11. https://doi.org/10.1080/08164622.2022.2106780
