It is often thought that too much screen time is damaging children’s eyes, but not spending enough time outdoors could be posing a bigger risk.
By Andrea Downey
Researchers from the Lions Eye Institute in Perth have been looking at the causes of myopia and found the amount of time people spend outdoors correlates to their likelihood of the condition.
While the reason for this is not explicitly known, it is thought to be linked to the amount of bright, natural light the eye is exposed to.
Myopia is caused when the eyeball grows too long from front to back, affecting the eye’s focusing ability. People with myopia can see objects that are near but have difficulty seeing objects in the distance.
Research suggests eyes that are not exposed to much bright, natural light in formative years – so in younger children and teenagers – tended to grow too long.
Professor David Mackey and his colleague Dr Samantha Lee from the Lions Eye Institute have conducted studies on myopia, as well as comparing other research, to better understand why cases are increasing.
Professor Mackey warned that we were in the midst of a global myopia epidemic, with environmental factors such as more time spent indoors partly to blame.
“In many cities in China, more than 90% of university students are living with myopia. Currently about six million Australians – or more than 20% of us – have myopia and we’re heading for 50% by 2050,” he said.
In one recent study, Professor Mackey and Dr Lee looked at the impact of screen time and when myopia develops. What was interesting was that looking at TV screens was not found to be having an impact, but reading books was.
“We found that about 14% of young adults developed myopia between the ages of 20 and 28 years. We also found that looking at small screens didn’t seem to have an effect, neither did watching TV,” Prof Mackey said.
“However, near work on larger computer screens did have an effect. So, we think that doing near work and reading books are doing the damage, exacerbated by children and adults spending less time outdoors in daylight and more time indoors for work or education.
“Our recommendation to Australian families is simple: increase the amount of time your kids spend outside, aiming for two hours a day, but follow SunSmart guidelines.”
Seeing the signs
While parents have an important role to play in making sure kids spend enough time outside, so too do GPs, optometrists and ophthalmologists.
Often the family GP might be the first to notice a child is having issues with their vision as they are the first point of contact for routine check-ups or any health concerns parents might have, says Professor Mackey.
“The risk factors to look for if a child is becoming short-sighted are if their parents are both myopic, that puts your risk up a fair bit,” he said. “Or children who are struggling with school or any other educational problem, it is worthwhile having an eye check because occasionally we pick up problems in younger children.
“It’s usually when a child is complaining they can’t see the blackboard. You can sit them a bit closer, but then if they are still struggling then you go and get an eye check.”
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Dr Lee adds that GPs should ask parents about their child’s vision during routine check-ups and refer to an optometrist if any concerns are raised.
“A lot of people only realise they have myopia when they go for their driver’s license because when you’re a kid and everything is blurry you just think that’s how the world is,” she said.
“It’s something parents could be more aware of – asking their child if they can see street signs that are far away, and if they can’t, maybe it’s time to get their eyes checked.”
Measuring up
Professor Mackey and Dr Lee have identified a simple test that can guide which children should be treated for myopia early.
Similar to height and weight measurements taken during childhood, they suggest routinely measuring children’s axial length – the length of each eye, from the front of the cornea to the back of the eye.
“We need to identify children with severe myopia earlier in life so we can intervene and avoid a lifetime of challenging eye disease leading to blindness,” Professor Mackey said.
“Some children will just have longer eyes, but if the axial length increases faster over time, that’s a good predictor of future myopia.
“Preschool and primary school children at greatest risk will need interventions, which include increased time outdoors, low-concentration atropine drops, peripheral defocus lenses and possibly other treatments being investigated.”
They suggest all ophthalmologists and optometrists working with kids should use the test and hope that in the future it will be globally adopted as a routine preschool screening test.
In Western Australia, there is currently no routine screening test for myopia or other visual impairments, but the picture varies across Australia. In New South Wales, for example, they have the StEPS program which offers all four-year-old children free vision screening before they start school.
Dr Lee said a national approach to eyesight screening, such as the StEPS program, would help to identify cases of myopia earlier, but in the absence of a screening program, the onus falls to GPs and other health professionals to check a child’s vision and refer if issues arise.
Increasing globally
Cases of myopia are increasing worldwide. The World Health Organization predicts myopia will affect 52% of the world’s population by 2025.
While genetic factors are at play, studies have shown the near work we do – like studying and working on a computer – are also a risk factor because they hinder time spent outdoors.
Studies have found cases to be higher in countries including China, Japan, Korea and Singapore, where intensive education is often undertaken from a young age, but increasingly places like Australia and Europe are seeing more cases.
RELATED: Myopia in children
“People have been blaming screens for myopia since televisions came around and then it was computers, then laptops and more recently smartphones and personal electronic devices,” Professor Mackey said.
“However, the myopia epidemic in Asia happened back in the 1980s before most of these devices came about and it was actually the near work they were doing, so reading books and holding things close.”
He said the amount of time kids spent inside during their school years, alongside the intensity with which they study both impacted the eye’s development.
“All of it interacts with the amount of time spent outdoors,” he said.
But he adds it is not to say that children need to study less or stay away from screens, it just needs to be countered with time outside like reading a book on the veranda or walking to school.
One study compared the prevalence of myopia among children aged six and seven of Chinese ethnicity in Sydney and Singapore.
Children living in Sydney had a significantly lower prevalence (3.3%) of myopia compared with those in Singapore (29.1%). The children in Sydney read more books per week and did more total near-work activity but spent about 10 hours more outside each week than children in Singapore.
Researchers concluded that the lower prevalence of myopia in Sydney was associated with increased hours of outdoor activities.
Slip, slop, slap
Using the Busselton Healthy Ageing Study, Professor Mackey and Dr Lee’s research has also shown those who have had skin cancer are half as likely to have myopia.
They are now looking at the practicality of spending more time outside in a country where skin cancer is also a major risk.
“We already know that spending time outdoors does slow down the onset of myopia, but what we want to do with this research is see how feasible it is in Australia where we have the problem of melanoma and skin cancer,” Dr Lee said.
“What we are encouraging people to do is spend time outdoors in the early mornings before 10am and later in the afternoon after 4pm when the UV index is below three.
“That way they get the benefit of the bright outdoor sunlight without the strong UV levels.”
Even when the UV is at its lowest, it is still important to take sun precautions like suncream, a hat and sunglasses.
Dr Lee adds that getting outside is the cheapest thing parents can do to help prevent myopia. Once myopia has begun, it cannot be reversed and if left unchecked can require expensive treatments.
For some this may mean the inconvenience of glasses, but in more severe cases it could mean special lenses, corrective contacts that are worn at night, or atropine eyedrops. Risks also may include retinal detachment, glaucoma, myopic maculopathy and even vision loss.
According to Global Burden of Disease uncorrected distance refractive error, which occurs when the eye is misshapen such as in cases of myopia, is the third largest cause of blindness.
Prof Mackey’s message is clear: health professionals and parents need to be aware that cases of myopia are increasing and if left unchecked will cause lasting damage.
“What they are seeing now in China where there are so many young people with myopia, there is a huge rise in vision loss from myopic maculopathy,” he said.
“It’s not just a cosmetic inconvenience issue, it is that the rates of irreversible blindness will go up if we don’t control the myopia epidemic.”
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