State data to be used to limit child gamers in China
bbc.com
bbc.com
china is learning well with the west.
Huh, I thought the current prevailing theory was that it was caused by lack of bright daylight, not by too much reading or to many hours in dim light. So a certain number of hours outside a day should have a protective effect.
Nothing to do with reading or studying (i.e. "eye strain"); it's purely the poor light.
Facts for fun, from what studies I've read on the subject:
Photosensitive retinal ganglion cells produce dopamine when they're struck with daylight-like light levels; this dopamine affects the flexion of the musculature around the eye, which in turn affects the shape of the eye as the eye, those muscles, and the bones of the skull all develop and grow together (the muscle under flexion "reserves" more space for itself, so less is filled with bone, and so, when relaxed, it allows the eyeball to expand.)
The human body has evolved to assume this effect, and so the eyeball develops into a "normal" shape only under the presence of this chronic photo-mediated local dopamine release. Without it, the eye develops into a more ellipsoidal shape, distorting the cornea.
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One thing I haven't been able to glean from these studies is what light level qualifies as "daylight-like." Do the photosensitive RGCs activate only under full sunlight (~100K lux); with shaded sunlight (~10K lux); on overcast days (~1K lux)?
My own hypothesis is that the limit lies somewhere between "shade" and "overcast", since a lack of photosensitive RGC stimulation leading to a lack of SCN-mediated dopamine release to the brain generally, is a good explanation for Seasonal Affective Disorder; and—more anecdotally—the symptoms of Seasonal Affective Disorder seem to me to line up with the common experience of living in regions of the world with persistent overcast weather (e.g. London, Seattle/Vancouver, Tokyo.) I'd love to see a study of whether those regions have higher-than-normal levels of nearsightedness in the populations that grew up there (though this effect might be totally invisible next to larger effects like differing choices in indoor/outdoor activities for children.)
Probably any ophthalmology textbook would go into the development of the eyeball, though I'm not sure the science of the effect of light on said development is old enough to have made it into any of those textbooks. I think current textbooks would explain that myopia is caused by a distortion of the shape of the eyeball during development, but wouldn't attempt to go any deeper into why that distortion occurs.
Edit: in China