I wonder if our eyes need campfires when we are older, just like they need bright sunlight when children in order to properly develop and function. (Myopia is caused by insufficient bright light as a child.)
Tentative evidence indicates that the risk of near-sightedness can be decreased by having young children spend more time outside.[4][7]
So that's a very, very much weaker claim "time outside may affect ..." and acknowledges the role of genetics and other factors. Of those 2 references I looked at
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5599950/
I declare I have no expertise in the field but also didn't find the meta-analysis paper convincing.
Looks the most promising. I couldn't find a replication.
So there could be something in "time outside" as a beneficial preventative measure for some children w.r.t. myopia. There is nothing much like "Myopia is caused by insufficient bright light as a child" as I understand that sentence. But maybe I've misunderstood?
Not having a full explanation when there isn't yet one is ok. Genetics is clearly and obviously a major predictor of developing myopia. Any explanation not taking genetics into account is likely very wrong. Or we're goipng to be amazingly surprised! (And maybe in a good way! But sadly, I doubt it.) Genetics explains why being tall is much more prevalent in the Netherlands now. Always had those genetics, now with better nutrition. Eh, hopefully we'll find out.
(Now we've had the relevant part of the conversation will you please humour me as I whinge like a 3 y.o. about how much it s&%ts me on some of the days I can't see straight? Good. Thanks. As you were...)
Certainly in some cases it is caused by genetics, but from what I've read, the evidence suggests that some other factor is at play for the overwhelming majority of cases. Here is an excerpt from a nature article which leads me to believe that this is the case.
> East Asia has been gripped by an unprecedented rise in myopia, also known as short-sightedness. Sixty years ago, 10–20% of the Chinese population was short-sighted. Today, up to 90% of teenagers and young adults are. In Seoul, a whopping 96.5% of 19-year-old men are short-sighted.
I don't know how that change is possible in one generation if genetics are to blame. It's possible I'm missing something though.
What proportion of the population had their eye sight measured 60 years ago in China (or anywhere)?
Is it certain that we are comparing like for like? Many more people everywhere do work that requires a lot of reading now than 60 years ago even in the northern Europe so perhaps myopia is more often diagnosed now simply because it is more of a problem in the modern environment.
You don't necessarily have to have measured the prevalence of myopia among children 60 years ago to extrapolate from the prevalence of myopia among 70yo today (since myopia is, by and large, a progressive condition and not typically reversed spontaneously).
Sure, you have to be worried about selection biases of all sorts including survivorship bias (eg. suppose myopic people mostly died before they reached 50), but in general, if myopia is as high or higher among 20yo than 60yo today, it tells you something pretty darn significant.
Campfires have a LOT of deep red light.