All about outdoor time

• Time spent outdoors is beneficial for physical and mental health in children and teenagers, and has also been shown to reduce the risk of myopia.
• Myopia (also called short-sightedness or near-sightedness) can be delayed or prevented in children by aiming for two hours per day of time spent outdoors.
• The activity of outdoor time doesn't appear to matter, as the benefit appears to be the brightness of light stimulating a correct rate of eye growth.
• Sun protection is still important, and even if wearing a hat, sunglasses and staying in the shade, the light brightness outdoors is strong enough for beneficial effects.

There are a lot of beneficial effects of time spent outdoors for general health, and this is true for eye health too. Much evidence points towards the benefits of increasing time spent outdoors in preventing or delaying myopia in children.¹

Myopia is an eye condition which causes blurred far vision, and is also known as short-sightedness or near-sightedness. Once myopia develops in children and teenagers, it typically deteriorates every few to several months. In most cases, this worsening continues until the late teens or even early 20s.²

This is called progressive myopia, which is a significant concern to quality of life in children and teenagers, and also poses risks to long-term eye health.³

Spending time outdoors can benefit a child's physical, mental and eye health - increasing activity levels and fitness, reducing sedentary (sitting) time, and promoting social and emotional well-being.⁴ Teenagers and young adults report feeling physically and mentally better when spending time in nature.⁵

Spending at least 13 hours per week (just under 2 hours per day) outdoors has been shown to reduce the likelihood of children becoming myopic, across multiple research studies.⁶

Increasing time spent outdoors has also been shown to have a positive effect on slowing the deterioration of vision in children with myopia.⁷ This can provide an additional benefit for children and teenagers undergoing myopia control treatment, to reduce their myopia progression.

Scientists are still discussing the mechanism of how time spent outdoors can work to prevent or delay myopia. It doesn’t appear to be that the child is simply not reading, as one study found that even children who read a lot still got the benefit of time spent outdoors to protect their vision.⁸

It also doesn't appear to be about physical activity - another study found that children who had myopia and those who weren't didn't have any differences in their activity levels.⁹

Instead, the stronger influence may be the brightness of outdoor light.¹⁰ Outdoor light is much brighter than in any condition indoors, even when comparing a cloudy day outdoors to bright indoor lighting. If a child wears a hat, sunglasses and plays in the shade, light levels are still brighter to the eye than with large windows or bright artificial lights indoors.¹⁰

The brightness of light is theorized to stimulate chemical signals in the retina, the light sensitive layer at the back of the eye, to grow at the correct rate. In childhood myopia, the eye grows faster than the expected childhood rate, leading to blurred and progressively worsening far vision.¹¹

Another potential benefit of outdoor time for the visual system is that the environment stimulates the whole field of vision more evenly, with all objects being further away, compared to the indoor environment.^12,13 There has even been a link found between lower amounts of 'green space' in urban environments and higher levels of myopia.¹⁴

Sun protection is extremely important for children. Around one-quarter of lifetime UV exposure occurs before age 18¹⁵ and children wear sunglasses less than a third as frequently as adults.¹⁶

Excessive sun exposure can lead to eye diseases in later life such as eye surface disorders, cataract and age-related macular degeneration. This means it's important to set up good sun protection habits from a young age.¹⁷

The good news is that a child or teenager can get the benefit of the brightness of outdoor light even when being sun safe. Research has shown that if a child is sitting in the shade while wearing a hat and sunglasses, the level of brightness reaching the eye is still far brighter than in any indoor situation, and enough to help protect against myopia.¹¹

Any activity seems to be beneficial. Research has shown that it’s not physical activity that is the key factor in the benefits of outdoor time for preventing myopia, but more so the brightness of the surrounding light. Kids who had similar levels of physical activity had different outcomes for their eyesight if they didn’t get enough time outdoors.⁹ 

What about using a digital device when outdoors, such as in the back garden at home? Research hasn't provided the answer for this particular scenario yet, but it is known that looking at close-up objects (like a book or hand-held digital device) for extended periods of time is linked with myopia in children and teenagers.¹⁸

While physical activity doesn't have to be undertaken to get the benefit of time spent outdoors for children and teenagers, it is still very important for general health. Whether done indoors outdoors, these recommendations come from the World Health Organization's guidelines on physical activity. These recommendations are made for each 24-hour day.

• Infants (less than 1 year old): should be physically active several times a day in a variety of ways, with more being better. They should not be restrained for more than 1 hour at a time (eg. prams, strollers).
• Children 1 to 2 years of age: at least 180 minutes (3 hours) per day in a variety of physical activity types at any intensity, spread throughout the day, with more being better. They should also not be restrained for more than 1 hour at a time (eg. prams, strollers).
• Children 3 to 4 years of age: at least 180 minutes (3 hours) of activities of any physical intensity, with at least 60 minutes being moderate-to-vigorous activity, and no more than 1 hour at a time restrained.
• Children and teenagers 5 to 17 years: 60 minutes average per day of moderate-to-vigorous intensity physical activity, mostly aerobic, spread across a week. Both muscle strengthening activities and vigorous aerobic activities are recommended.

There are three key rules for the childhood visual environment – outdoors which are important for both reducing the risk of a child developing myopia (short-sightedness) as well as reducing the risk of fast progression, or worsening, once a child or teenager has myopia.

1. Aim for your child or teenager to spend two hours per day outdoors. While this can seem hard to achieve in our busy lives, it may be mostly achieved at school for primary-school aged children, when this intervention is most crucial to prevent or delay myopia. On the weekend, plan a family outing – even a walk to the local park and a short play will help the minutes tick away.
2. Don’t forget sun protection – hats, sunglasses and shade. Your child or teenager will still get the vision, eye health and physical health benefits of time outdoors without excessive risk of sun exposure.
3. Kids should be physically active for least 60 minutes a day. This should be moderate-to-vigorous level activity. If this is spent outdoors, all the better for their visual development. Again, for primary school aged children, this may be mostly achieved in break times.

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