Please note that this is not my area of expertise, I'm just doing my best to pull together and interpret the available information.
In this article, I'll focus on the increase in myopia in children and whether screens are the culprit.
MyopiaMr David Allamby, a laser eye surgeon has been in the press recently talking about the effect of screens on distance eyesight. He says that spending a lot of time looking at screens close-up can cause myopia (short or near-sightedness) which is poor distance vision. He thinks this is because they are not spending sufficient time looking at things that are far away. Our ancestors spent much more time outdoors. You can listen to Mr Allamby talking about the related research and his experience in this radio interview.
According to a report in the Lancet medical journal "The higher prevalence of myopia in east Asian cities seems to be associated with increasing educational pressures, combined with life-style changes, which have reduced the time children spend outside."
Myopia in children does seem to be increasing. There's no genetic explanation for this over the short term so we need to look to environmental and lifestyle factors.
One theory is that spending a lot of time focusing on things that are very close is a problem. This isn't usually described as an issue with screens per se, although children may hold smartphone and tablet screens too close. Reading and crafts that involve close work, for example, would create the same issues.
Surprisingly, there doesn't seem to be a huge amount of evidence that near-work is a major cause of myopia. One of the commonly cited papers in this area reports that:
"Because myopic refractive error tends to have its onset and increase progressively during the school years, intensive near work, particularly reading, has been hypothesized to lead to myopia Although this idea is intuitively appealing, particularly because of the obvious links between near work and accommodation, to date near work has been shown to make only a small contribution to the overall prevalence of myopia." Rose et al
The same paper, Outdoor activity reduces the prevalence of myopia in children,
shows a more significant link between increased outdoor activity and reduced levels of myopia in children: "The lowest odds ratios for myopia, after adjusting for confounders, were found in groups reporting the highest levels of outdoor activity."
Some scientists have suggested that focusing on far away objects is the reason that being outdoors helps reduce myopia, others think that exposure to natural light or other aspects of the outdoor environment may play a role. One possibility is a lack of vitamin D in children who spend a lot of time indoors. This seems to be an area where more research is needed.
However, a recent study reports that "Despite protective associations previously reported for time outdoors reducing the risk of myopia onset, outdoor/sports activity was not associated with less myopia progression following onset. Near work also had little meaningful effect on the rate of myopia progression." This suggests that there may be something else going on that is not yet understood.
ConclusionHmm. The research in this area is far from conclusive. More research is needed to understand the causes of myopia in children and advise parents and educators on the best ways to avoid it.
Screens themselves don't seems to be responsible for causing myopia, but a lifestyle that includes too much screen time instead of spending time outdoors may be an issue.
For now, for me personally, this is another reason to encourage my kids to spend more time outdoors which is a good thing anyway.
But I'd really like to have a deeper understanding of issues at play here.