As one meta-analysis put it:

It’s estimated that an increase of one hour per day of outdoor time could reduce the occurrence of myopia in children by 45%.

Make sure your kids spend time outside, folks!

I was outside a lot and still got myopia :3

Congrats on the luck

Same for me, I spent most of my free time as a child playing outside. I grew up in California, weather wasn't a concern, I was outside year-'round. I got my first pair of glasses at age 21. I suspect it's far more genetic than environmental.

did not seem to help me. I guess I got the bad side of the coin flip.

Is this really causation though? Could it not just be that kids that spend less time looking at screens are less likely to be short-sighted AND more likely to spend time outside?

Then you were likely genetically predetermined to be at least a little myopic, but if you spent less time outside during your developmental phases you would likely be even more nearsighted than you are now.

If you get this type of short sight vision, you can train your eyes to get the vision back as this is caused by the eyes strength.

But if you have the type that has to do with your eye shape going outside will do nothing, and you can exercise it away

Ysk 0*infinity = 0

If you spend no time doing anything that you ought to do (exercise, go outside, eat healthy) the immediately observable effects from any amount of sustained practice is measurable.

It wasn't mentioned in this article, but I remember reading somewhere that it might be because exposure to sunlight affects vitamin D production, which affects the length/shape of our eyeballs as we're growing up.

Yes, I spent 6 months in ICU in 2014, I had a lot of eye issues while I was there not related to my reason for my stay (bilateral lung transplant) but as side effects of procedures and meds but I also basically lost my depth perception unless it was directly in front of me. Living in a 10x10 room for half a year with no far away distances to observe made my eyes weak, it took about six months after I got home to get my full depth prescription back. Indoors just makes your eyes weak, mine is an extreme example, but it doesn’t permanently ruin them.

I'm farsighted, so I can only conclude that I spent too much time outdoors as a kid. See Mom!?

Another idea is that when you're outside, you spend more time focusing on objects further away, which helps develop those eye muscles

If this is just a correlation this would have to be a correlation at the population level. Countries where kids start school later on (e.g. 7 years old) have significantly lower rates of myopia than countries that start school early on in a child's development (e.g. 3 years old). It's still possible that this is a correlation, but the correlation would have to be capturing something deeper than just an individual kids screen time. Granted, this correlation would still need to account for differences between individual kids, but it would also need to account for differences between kids at a population level. It's hard to see what could be causing this correlation though. So maybe there's something there we're just not seeing, but at a certain point though the idea that there is a causal relationship starts to seem like the most plausible explanation for explaining this data

You need to read better. It says it reduces occurrence of myopia in a population not that it cures myopia when an individual gets it.

Sure if you have very mild short term myopia caused by eye straining you can get vision back by training your eye. But with kids it’s about how the eye develops when it’s still growing. When kids eyes grow too fast they grow less spherical and that is what causes myopia and that is the kind that you can never cure. Going outside means kids are getting more sunlight in their eye which will slow down the growth and thus their eyes will grow more spherical which means they don’t develop myopia. Playing outside won’t cure myopia but it will reduce the chance of developing it in children.

It’s both. You can just look at the statistics, the number of people with myopia has gone up over the last few decades. If it was just genetics those numbers would have been stable.

N=1

N=1

I admit that I barely skimmed the article so I don't know if/how they controlled for this

But this also kind of feels to me like something that could go the other way- myopic kids are less likely to go outside

Get hit in the head by a baseball you didn't see coming or trip over a rock you didn't see a handful of times and you might decide that the "outdoors" thing isn't really for you.

Or of course a mix of both factors, kids who are already predisposed to short-sightedness go outside less, so the other factors at play make their eyes even worse and so they go outside even less and....

Yes exactly. But for people with near vision from eye shape there is nothing you can do exercise wise to restore vision.

But this also kind of feels to me like something that could go the other way- myopic kids are less likely to go outside

It's not just individual kids they are measuring, but entire populations of children and at what age they start school. The younger kids are when they start school, the more likely they are to be myopic, and this contributes to significant differences in the prevalence in myopia across countries (Edit: I should have stated this explicitly, but this is because more time in school means less time outside, generally speaking)

Hold up now. I grew up in the 80s when we spent the whole day outside, and I wore thick ass lenses all through grade school.

"Reduces chances" does not mean "prevents"

We spent so much time outside we developed near sightedness instead

A third idea is that sunlight is much, much brighter than most indoor artificial light, and the lack of this very bright light causes some sort of problem for the developing eye. Maybe the brightness of the sun is a sort of "calibration" method for the eye and when it doesn't get that really bright sunlight, the development of the eye goes out of whack.

So is it vitamin D, or far-away views or bright sunlight? I've heard all these theories before but I'm not sure which is it. Does the meta analysis say anything about which effect is most likely the cause? I mean could we "fix" this by going outside to view things far away, or should we just take vitamin D supplements, or should we have much brighter indoor lighting? I'd love to know.

YSK: The word is 'spent' not 'spend'.

You should have “spend” the day outdoors not “spent”.

well, i can concur. my eyes have trouble adjusting to looking into the distance when i have spent hours in front of the screen. they adapt after a few minutes to hours though.

irrelevant because the term used here was "odds", not chances

smfh

No. Spent is the past tense of spend.

Yeah that was a typo. Edited the title to fix it, should be correct now

A third idea is that sunlight is much, much brighter than most indoor artificial light

Would this mean it’s a bad idea to give kids sunglasses?

Does the meta analysis say anything about which effect is most likely the cause?

Not that I saw though I admit I didn’t read the whole thing

How do some people despite being wrong are happy to correct others? And they have up votes? Wtf...

Well, unless nearsighted people were outcompeting people with 20:20 vision, for some reason.

Uh OK same reply

My comment only makes sense with the original misspelled title of the post.

They edited the title.

Ohhh, I see. I thought you were just a really bad grammar Nazi.

damn people on Lemmy don't like sarcasm huh

"Also, while various theories such as increased light exposure, release of dopamine from retina, increased depth of field have been suggested to explain the protective effect of outdoor time, the mechanism remains to be elucidated"

Correlation is not causation.

My eyes have been terrible since 1st grade. My prescription got as high as 9s.

Then I got cataract surgery on one eye, and I can see nearly perfectly without glasses for the first time in my life. This summer, I'm getting the other one done, and I won't have to wear glasses anymore, for the first time in my life.

Anyway, the point is: As I was talking to the eye surgeon, and mentioned my bad eyesight, he told me why: I have the eyeballs of a man who is 7'2" tall, jammed into my 5'11" skull. Apparently, I have enormous eyes, which nobody has ever mentioned to me, other than one brief girlfriend who used to comment on my gigantic green eyes.

If I had to get something big from a 7'2" inch man, why did it have to be eyeballs?

Yeah, I always had terrible eyesight, and I probably spent more time outside than inside. There was nothing fun happening in the house. ALL the fun was outside.

You prefer big feet?

You can establish causation even if you don't know what the mechanism is. I don't know to what extent causation has been established here though, I'm not familiar enough with the research. But at minimum the intuitive idea that there is a noncausative correlation because kids with bad eyesight choose to stay inside more does not seem to stand, since this phenomenon can exist at a population level (so countries where schools start younger - and kids go outside less - have significantly higher rates of myopia).

Wow I didn't realize that cataract surgery can improve your vision that dramatically. I thought cataracts surgery was something typically reserved for seniors to prevent foggy vision

I don’t know to what extent causation has been established here though

I am familiar with the research. We don't know the reason for nearsightedness. There is no known proven causation. It is likely there are different causes for it.

Being from a sunny country lowers the chance of it (so you're less likely to be nearsighted if you're from Spain compared to Norway), even when controlled for hours spent outdoors.

Being from a sunny country lowers the chance of it (so you’re less likely to be nearsighted if you’re from Spain compared to Norway), even when controlled for hours spent outdoors.

This is very interesting

That depends entirely on how the correlation is determined. For example randomized control trials can establish causal inference.

There have been RCTs conducted for this. For example

Myopia Prevention and Outdoor Light Intensity in a School-Based Cluster Randomized Trial

Pei-Chang Wu et al. Ophthalmology. 2018 Aug.

In this study, schools were selected and promoted either outdoor or indoor recess

There are studies that just look at outdoor time. I don’t think we know the specific mechanism but we know enough to have recommendations.

If we take your eyeballs and take my teeth ("You have the roots of a 6'5" man" inside my 5'4" female body) we have the start of a good build!

Which of us is Doctor Frankenstein though?