Ok, that's a thing, but it's right in the name, it's transient. I mean, we don't _know_ for sure what causes myopia, and it does seem there is something with our lifestyle, I am just not convinced that the obvious answer "staring at close things" is the correct one. In my experience as someone with myopia, staring at close things is a side effect of myopia, in that you need to get closed to see, and, I presume, not the thing that causes it, but a really fun confounding factor.
And to @heavenlyblue - don't worry, people have been saying the same things about books as well. I remember reading "Diary of a Short-Sighted Adolescent" and his parents wouldn't let him read because he was short sighted, y'know, for his health. The belief that stairing at close things is causing myopia is common, but, as far as I can tell, not based on any conclusive science. It's just that recently it's more in vogue to be concerned by technology than by books, and, beside, these days, most people stare at screens and phones rather than books.
