is Harry near-sighted or far-sighted and why?

In respect to the films, he's most likely long-sighted (which means he can see distant objects) which is why he would have to feel around for his glasses, he has to squint to see the snitch because it's so small and quick that it's hard for anyone to see it. Hope that explains it.

I'm pretty sure Harry is severly near sighted and maybe on his way to having to use bi-focals (for both near and far sighted). I'm near sighted myself (meaning I can see close up like at books, but even a foot away from something I have trouble seeing it). When you have to wear glasses, you have to update your prescription every once in a while so maybe Harry squints to see the snitch because he needs newer glasses? Or it might be that, like most people that wear glasses, you have a bad habit of squinting a lot...I know I do.

He's normal he doesnt need glasses in real life, and he could have a stigmatism.

He might be farsighted in one eye and nearsighted in the other. It happens. My eyes are like that.