It's a risk mostly to small children as far as I understand. There's been a few case of semi-permanent eye issue I think in pretty young kids (6 or so ?), and temporary issues in older kids (10-13?), but I can't find the papers back.

Since these studies, it has become harder to experiment on small kids as it would be unethical, but on the other hand there's no specific report on kids older than 13 if I remember well.

Then a decent number of adults have been using the headsets for prolonged periods without anything critical reported at this point. It should still be used with awareness of potential risks, but I don't think there's any strong evidence of long term effects.

As covered in the original announcement discussion, it has lens inserts that increase the focal distance.

>if the eye no longer has to focus on [different distances]

The same problem exists with monitors. The recommendation is take breaks to focus at different distances.

I don't know - monitors are physical objects in space that you are aware of. I would classify Vision Pro more as glasses.

I wear glasses myself. And sometimes I forget to take them off because they become part of my perception. That doesn't happen to me with my monitors :-D