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I keep hearing this, but I spent a lot of time outdoors as a child. Hours every day, riding bikes with friends and running around with BB guns in the woods. We played a lot of video games and read books, too, but we spent plenty of time making tree forts and "sword fighting" with old pipes. Still needed glasses by the age of 7.

Obviously, genetics also plays a role in individual cases. We're talking about the population level here, and genetics doesn't explain the myopia epidemic, because population-level genetics hasn't changed rapidly. Time outdoors has.

I believe that more screen and reading time causes more childhood myopia. That seems hard to refute. I just do not believe, without serious peer-reviewed studies, that "a couple hours a day outside" is the magic cure. Out of my friend group, 3/4 of us needed glasses, and we definitely met the "couple hours a day outside" criterion. But we also loved our Street Fighter 2.

Various peer-reviewed studies exist and have been covered by pop science articles over the past 15 years or so.

Here is an example one; there are likely dozens available.

Study with 65 citations: https://pmc.ncbi.nlm.nih.gov/articles/PMC7607527/

Pop science article with more context: https://www.theatlantic.com/health/archive/2014/05/nearsight... (https://archive.is/OeuC3)

Thanks! The first study is interesting because it links axial eye growth inhibition to high light levels, not necessarily being strictly outdoors (UV) nor avoiding close-up activities like reading. Interesting.

"High light levels" makes it sound like you could just replace 50 watt bulbs with 100 watt bulbs indoors to fix the problem. It's not like that at all. Sunlight is dramatically brighter than indoor lighting, far more than people realize. It would be impractical to replicate sunlight brightness indoors for many reasons: energy consumption, the cost and size of the fixtures, the immense heat it would produce, and generally because it would be uncomfortable to have light sources that bright in close proximity to you.

And again I am skeptical of claims that it is just one factor like brightness alone. There is other research about spectrum and distant objects in view that also shows effects. So even if you did use 100x brighter lights in your house there's no guarantee you would fix the problem.

Here's your review:

https://pmc.ncbi.nlm.nih.gov/articles/PMC9114237/

Just anecdata, perhaps, but same.

I did nerdy kid stuff like read lots of books and use computer screens (uncommon back then, I'm 52)... but I also played outdoors for hours nearly every single day.

Ended up with vision at -6.00 by the time I was a young teenager (don't remember the age it started to slide that way but would estimate around 7-8 or so). Hasn't gotten any worse (or better) since then.

Same here. Both parents though wear glasses from young age so I think genetics will always be the main factor.

In my early teens I had 20/15 vision. By my mid teens I was into computers and wearing glasses, despite copious time outdoors.

I don't think that's true at all. I had prefect vision up until I graduated college and started spending 10hr a day behind a screen - within two years I ended up getting glasses, although they are a mild prescription and I don't really need them other than driving at night. My friend was in a similar position and they also ended up getting almost the same prescription.

My eye doctor said it was my eyes optimizing for what they do the most. And that makes sense, I have no eye strain using a computer.

Interestingly my vision is better in the summer, and when I take holidays during the summer and spent time away from the computer my eyes essentially fix themselves. It takes a couple months back behind a screen to need my glasses again.

Counterpoint: I have spent 10hrs a day in front of screens since I graduated from college and my eyes are fine.

Definitely a genetic component as well!

Yes but it's might just be a different mechanism from childhood -> adult myopia. Where you go from perfect vision to -5

> But ultimately some combination of these factors provides the signal to your retina to stop growing once it reaches the right size, which prevents myopia.

Are you conflating retina with eyeball? In some/many cases, it’s the length of the eyeball being too long for correct focus on the retina. The retina doesn’t keep growing and cause myopia.

It could be both. And focus distance may matter. Like, books may also cause myopia. Reading books outdoors may be a bit better than reading books indoors. Using screens at a distance could also be benign.

Ha! My parents also thought this was the case, I was a child before the internet and phones, my favourite hobby was playing around in the trees next to our soviet commie block.

I had an incredible childhood with building hidden dwellings in the woods, unsupervised fires and bicycle journeys, football, building ice castles etc, swimming and martial arts lessons. My parents even limited my TV time to 2h a day.

But I still had —1 myopia for every grade until 7th.

My analysis is that by that time I got into reading books - both science and fantasy, and then boom my eyesight was fucked.

Thank god for LASIK.

>My analysis is that by that time I got into reading books - both science and fantasy, and then boom my eyesight was fucked.

When I became a heavy reader I speedran long sighted to short sighted. I think 4th grade I got my long sighted diagnosis. 5th grade I started lifting heavier books. By the end of 7th I had more or less the prescription for Myopia I have now.