[pbazarnik]

Exposing eyes to sunlight (or high intensity light) is a very important factor preventing and reversing myopia [1]

There was also Australian paper I cant find now, showing that prevalence of myopia in Asians in Australia is much lower due to school systen encouraging more free time and play outdoors. (not explainable by genetic factors)

Children must play outside in the sun or they become myopic.

[1] https://pubmed.ncbi.nlm.nih.gov/29371008/

[qsdf38100]

I heard that playing outside also generally makes you focus on much more distant objects, and that as the eye optimizes for a "at rest" focal point that best fits what you're looking at most of the time.

So when you're looking at close screens or books for most of your day, the eye makes that be the "at rest" state, but now distant objects are blurry. Now if you insist on having distant objects not blurry (by wearing glasses _all the time_), it's the same situation again and the eye will "adapt" even more, and you'ell get more power glasses, and so on...

If that's true, then people with myopia shouldn't wear their glasses _all the time_, particularly when staring at close objects (screens and books). I have myopia and that explanation fits my experience. Most of the time I'm looking at a screen not wearing my glasses, and the screen is exactly at the right distance for me to not to have focus, so my eye is "at rest" for most of the day.

It sounds weird that a lot of eyes are dysfunctional. Maybe we don't understand how eyes find a trade-off that best suits your average focal distance. It also gives a rational as to why myopia went from a few 1% to 50% of the population in some countries. People started staring at close objects.

I don't know if it's actually true, but it makes a lot of sense to me.

[Laforet]

Focus or accommodation loss is just the beginning of myopia. Sometime after the symptoms show up, the eye would physically elongate in the axial direction and push the retina beyond the accommodation range of the lens. This change is impossible to "reset" with current medical knowledge.

Your idea about allowing the eye to "rest" is not new and it has been the subject of several large scale clinical trials such as the COMET study linked below. In short, under correcting myopia does help to slow down progression. However, the benefit is too small to justify not fully correcting vision which will result in a better quality of life.

https://pubmed.ncbi.nlm.nih.gov/11578789/

[qsdf38100]

I see, this study does seem to rule out my view. What's the current consensus about why myopia progressed so quickly in some countries?

[Laforet]

The traditional view has always been a combination of genetics and behavior factors, namely reading and other close up work during the age of 8-14 when the eye is still capable of axial elongation. The light intensity theory is a more recent development which has some merits, but more evidence is needed for proof.

After WW2, Canadian Inuits started to send their children to school for the first time in history and myopia became endemic from that generation onwards.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1956268/

And to put the source in context:

- This was before the age of computers and smartphones so screen time was much less of a factor.

- Inuits traditionally spend a disproportionate time indoors due to the climate.

- The schooling was likely shorter and less stressful than those found in places like Japan and Korea, yet the effects are just as apparent.

Similar rises in myopia rate was observed when daily schooling was introduced to many other places, but few occur on the same scale. Thus it is possible that Asians and Inuits are genetically predisposed to myopia and it took until the modern age for this to become a problem.

[akiselev]

> So when you're looking at close screens or books for most of your day, the eye makes that be the "at rest" state, but now distant objects are blurry. Now if you insist on having distant objects not blurry (by wearing glasses _all the time_), it's the same situation again and the eye will "adapt" even more, and you'ell get more power glasses, and so on...

My optometrist specifically prescribes me lenses/contacts that are slightly worse than optimal (i.e. -2.25 instead of -2.5) based on the fact that I stare at a computer screen the entire day. IIRC her explanation was along these lines, and I've had no degradation in eyesight in nearly a decade since. (I am not an optometrist, for god's sake find your own)

[krackers]

You can get a separate intermediate distance pair specifically for computer use. If you're -2.25 then something like -1.25 would put optical infinity at 31 inches away allowing your eyes to be completely relaxed. I've got close to the same prescription and just prefer to keep my screen at 24" and increase the font size a bit, and I can see that just fine most days. I'm not sure if my brain has learned to deconvolve better, but around -2 is a sweet spot where you can definitely get away with not needing glasses at all for computer work if you try, considering that you're uncorrected plane is at 20 inches.

[coryrc]

Mine didn't and I also have not had any degradation in the last ten years.

[walterbell]

Everyone is different. It's unclear why some people benefit more from vision therapy than others.

[carlmr]

Same here.

[guyomes]

It seems that it is more specifically violet light [1] that reduces the development of myopia among children. One of the rational is that light triggers the production of dopamine in the eye, and dopamine prevents the eye from growing excessively during childhood, and thus prevents form-deprivation myopia [2].

[1]: https://doi.org/10.1016/j.ebiom.2016.12.007

[2]: https://doi.org/10.1016/j.exer.2006.09.018

[unhammer]

Should schools install blacklights?

[erosenbe0]

Outdoors play with visor/cap and UV protecting sunglasses (not heavy shading) is great for all kinds of development. Just use strategies to limit cumulative direct exposure to UV in childhood.

[demosito666]

So this would imply that myopia must be much more widespread in northern countries than in Asia, which I believe is not the case.

[unhammer]

In the Nordic countries at least, kids spend quite a lot of hours of the day outside in nursery/kindergarten/school as a rule (babies too: https://www.bbc.com/news/magazine-21537988 ) while as parent comment writes, school systems that encourage less outdoor time lead to more myopia.

There's less sunlight in the North during the winter, sure, but still several orders of magnitude more than inside (also, more UV etc.).

[_0w8t]

Sunlight alone does not explain it. Another possible factor is diet. It can be that eating a lot of carbohydrates with high glycemic index like white rice trigger slightly excessive growth of eye balls in children sufficient to trigger myopia. That also explain why moving to Australia affects this due to diet change.

But this hypothesis also has problems. For example, less refined carbohydrates apparently do not lead to this. Also it does not explain how adding more meat to refined carbohydrates affects the mechanism.