According to ABC News and this Ophthalmological study there has been a significant increase in the number of people with myopic eyesight over a recent 30 year period. From the ABC article:

There are multiple theories. Some say more people are now genetically susceptible to myopia. Others blame the increase on long hours spent in front of computer screens, possibly changing the shape of our eyeballs.

I myself A) use a computer about 12 hours a day (and have for quite some time), and B) am myopic (first having noticed in college, a few years after I began programming).

Perhaps anecdotal, I spoke to my ophthalmologist about this a decade ago and at that time he essentially said there is not enough evidence to show extended PC use causes myopia; however, he did say that myopia can sometimes be lessened in severity by spending more time each day focusing on distant objects (exercising the muscles in the eyes). To me, if one takes the contrapositive of that, it seems to imply excessive PC use might indeed lead to myopia.

At any rate, the (implicit) belief today seems to be that there is no causal relationship between increased myopia and increased PC use, but is that really the case? Or is it true there may be a genetic explanation for recent trends?

  • Related: skeptics.stackexchange.com/questions/404/… – Sklivvz Apr 10 '11 at 9:15
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    If focusing close for too long DOES cause myopia, then it seems that wearing corrective lenses would gradually worsen your vision as your prescription increases over time... – user6716 Apr 10 '12 at 13:26
  • There's a 2016 meta-analysis which predicts even more increases: from 1.4B people in the year 2000 (22.9% of population) and 163 million people with high myopia (2.7%) to 4.7B people with myopia in 2050 (that is 49.8% of the estimated future world population) and 938 million people with high myopia (9.8% of the world population in 2050). I stripped the confidence intervals due to comment length limit. – Fizz Dec 1 '17 at 22:52
  • @user6716 I wouldn't think it would because with the right lens your eyes are in a neutral state while you're looking at the screen. – Loren Pechtel Dec 3 '17 at 3:46

The reason may not lie directly in the increased time spent in front of a computer screen or TV, but the decreased time spent outdoors.

Sunlight could stop short-sightedness

Australian scientists from 'The Vision Centre' say there is persuasive evidence that increased exposure to daylight can prevent the permanent short-sightedness and eye damage...

The finding demolishes long-held beliefs that short sight is due mainly to reading, and overuse of TVs and computers by youngsters, or is primarily linked to genetic factors...

"The prevalence of myopia in the Australian population is dramatically lower than in other urban societies round the world – yet we do just as much reading and computer work," says Professor Ian Morgan of the ARC Centre of Excellence in Vision Science (The Vision Centre) and Australian National University.

The team’s conclusions are borne out by new research in Singapore and the United States, which has reached similar conclusions. (e.g.)

We’re seeing large increases in myopia among children in urban societies all around the world – and the outstanding common factor may be less and less time spent outdoors."

“The idea that ‘reading makes you short-sighted’ has been popular for a couple of hundred years. But recent data shows that the time spent indoors is a more important factor. Children who read a lot, but still go outdoors, have far less myopia.”

Our hypothesis is that the light intensity experienced outdoors – which can be hundreds of times brighter than indoor light – causes a release of dopamine, which is known to block the growth of the eyeball. This prevents it taking on the distorted shape found in myopic people. We are now testing this idea.”

[but] one of the potential problems with using increased time outdoors to prevent myopia is the potential for increasing skin cancers and for causing eye damage later in life.

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    Interesting. My vision was perfect up until 6th grade when it started sliding downhill. Corresponds perfectly to when I went from playing outside all the time to staying inside and reading. Of course, my Wife's vision is fine and she stayed inside all the time, never was one to go outside and play. Hmmmm. – Brian Knoblauch Apr 11 '11 at 13:17
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    I don't understand why they attribute the cause to the light's intensity. IMO the outstanding thing about seeing outdoors is, not the intensity, but that things are far away: indoors you never focus at infinity. – ChrisW May 20 '11 at 5:26
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    With the caveat that some (high) myopias are genetic, light intensity turned out to be most significant environmental factor known, verified in two recent interventional studies one in Taiwan, and one in China, and in one eye growth study. – Fizz Dec 2 '17 at 0:57
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    And mostly confirmed in a meta-analysis "Increased time outdoors is effective in preventing the onset of myopia as well as in slowing the myopic shift in refractive error. But paradoxically, outdoor time was not effective in slowing progression in eyes that were already myopic." – Fizz Dec 2 '17 at 1:28

I think Oliver had it right with respect to the most influential environmental factor (light intensity). I was a bit skeptical because near-work was a long-time favorite environmental hypothesis and yet the observational evidence about it was mixed. Near-work never got tested in interventional studies, as far I know. On the other hand, there is a recent meta-analysis of outdoor-time interventions, which has positive results:

enter image description here

Now let me say something about genetics; there are a few hints that inheritance alone could not explain the drastic recent trends in particular in East Asia:

enter image description here

A Nature news feature (from which that graph comes) called out the most striking of these

One of the clearest signs came from a 1969 study of Inuit people on the northern tip of Alaska whose lifestyle was changing. Of adults who had grown up in isolated communities, only 2 of 131 had myopic eyes. But more than half of their children and grandchildren had the condition.

More recently some of the genetic risk factor of myopia have been identified. But it also turned out that education is an environmental moderator for these (i.e. there's a gene-environment interaction). Another recent meta-analysis quantified this influence:

enter image description here

So the effect appears more significant in Asians than in Europeans. Also, education is easy to measure, whereas outdoor-light exposure is harder, but these two correlate (according to the paper).

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