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Comment by nickbauman | Hacker News Reader

I thought the increase in nearsightedness originated in kids not playing outside as much (and thereby not focusing their eyes over longer distances) resulting in eyesight that's more attuned to shorter distances.

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At least if wikipedia's summary is to be believed, that's one of the less supported of many potential theories. https://en.wikipedia.org/wiki/Myopia#Environmental_factors

Their summary seems to suggest that the biggest factor is exposure to daylight. So then even reading outside ought theoretically protect against nearsightedness.

> People, and children especially, who spend more time doing physical exercise and outdoor play have lower rates of myopia,[30][29][31][32][33] suggesting the increased magnitude and complexity of the visual stimuli encountered during these types of activities decrease myopic progression. There is preliminary evidence that the protective effect of outdoor activities on the development of myopia is due, at least in part, to the effect of long hours of exposure to daylight on the production and the release of retinal dopamine.

That sounds like a fair bit of support to me.

Can’t find it now, but there is also a comparative development study showing myopia and indoor electrification setting in together in different countries. Though that paper speculated blue light content, with a developing eye hard coded to “tune” its length on the assumption of sunlight.

> The near work hypothesis, also referred to as the "use-abuse theory" states that spending time involved in near work strains the intraocular and extraocular muscles. Some studies support the hypothesis, while other studies do not.[3] While an association is present, it is not clearly causal.[3]

This is what I meant. The GP comment included "and thereby not focusing their eyes over longer distances", which I interpreted to be in contrast to spending time indoors and looking at things close to you. So it's not that things far from you are protective, but specifically variety seems to be. So I think we mostly agree.

I played outside all the time when I was younger and here I am with my glasses :)

I've read that the amount of natural light is important, and that the light inside buildings and houses is not sufficient. Children should spend more hours outside.

If you have a light meter (on a camera or phone or standalone) it’s amazing how “dim” even the brightest indoor lights are.

Full flood wash on a stage is nothing compared to the power of the sun.

Some example values here

https://en.wikipedia.org/wiki/Lux#Illuminance

Office lighting: 250-500

Direct sunlight: 32,000-100,000

Yes certainly, that (and many other things) are more important factors. I'm not trying to say this is the only (or even a major) cause.

But that doesn't make it less interesting of a fact.

This is correct and how myopia works. Not because of an increase in natural light. There’s ample evidence for this.

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