The upside down glasses is a good example. As I understand it, after you get used to wearing them and then take them off, you see everything upside down with your regular eyes, and it takes a while to get back to normal. Doesn’t sound fun.

But in my case I don’t think even that would work. Elaborating further on the ophthalmologist’s words (and as another poster here noted), the neuroplasticity required to develop stereoscopic vision is just not there past some age. No amount of lens trickery will join the left-right circuits in the cortex.