Hacker News Reader

Comment by nsonha | Hacker News Reader

I don't know why western media always talks about myopia (in Asia) as if it's some sort of mystery. Where I'm from, everyone believes that myopia is caused by... the habit of looking at close objects for prolonged periods, such as electronic devices or books. Like how shocking (it should not if you know how muscles around your eyeballs work). I think it's even written so in the textbooks.

View on HN

Yes, that's a common belief in the West as well, and used to be generally accepted. But there's a very strong correlation between looking at close objects for prolonged periods and being inside so it's easy to understand why it was misunderstood for so long.

you seem to think the real cause is "being inside" and not using your eyes in a particular way? (looking at close objects...). What is the exact mechanism by which being inside affects your eyes then?

Artificial lighting? Less sunlight? Lower light intensity?

yes, there is a theory on how the muscles of the eyes become "miscalibrated", so to speak, if you only look at close things. What is the exact mechanism of the "lower light" theory then?

> 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.

thank you, I skimmed over this in the article

Please read the article. Its about that.

I'll try to explain what I understood from the article: the natural sunlight makes your body release dopamine, dopamine causes the eye not to elongate, not elongation equals not having near-sightedness.

Probably I got that only half right.

Anyhow the article claims it's not looking at close things and the real cause is being inside.

That's the subject of the article.

Close-up work (crafts, reading, computers) causing myopia 'makes sense', I heard the same thing as a kid in the States.

It makes me wish we would have had more P.E. classes outside, rather than 'giving our eyes a break' by playing kickball indoors under fluorescence.

the problem with playing indoor is that your "eye break" only goes so far as the walls of the space, still "close objects" in relative terms. In nature, humans use their eyes to gaze landscape, stars... really far things.

My understanding is that 20 feet or so is optical infinity, so whether you're looking at an object 20 feet away or 20 light years away, your eye muscles are just as relaxed (hence the 20-20-20 recommendation: every 20 minutes, stare at an object 20 feet away for 20 seconds)

I don't know about you, but where I spent my childhood, most things indoors were much closer than 20 feet away.

That's a fairly large room, and we typically don't focus on the furthest point while indoors anyway. So with the 20ft requirement, it's a lot easier to fulfill while being outdoors.

Oh yeah definitely - I was purely commenting on the parent comment's "really far" claim, and noting that it's all the same to the eye muscles once you hit 20 feet - you don't have to (no pun intended) set your sights on the stars to relax your eye muscles.

Well, the real problem is that children's eyes aren't getting enough sunlight exposure to trigger dopamine production, which regulates the lengthening of the eyeballs, while cooped up inside. Eye strain is muscle fatigue, unrelated to myopia.

This used to be the leading theory, indeed. Turns out it was wrong, as the article explains.

Reply on news.ycombinator.com