The vision therapy I'm aware of is not about improving eyesight per se
as much as it's about improving tracking ability.

I think though, that poor tracking can mean you test as needing glasses,
but they aren't a full solution, but can still help partially, sometimes
a lens can force your eye to work in a certain way, thus changing how
it works and potentially being part of correcting some kind of vision
problems. I'm trying to dig around in my mind for what I needed glasses
for, I know they definitely had in long sight lens, rather than those
for short sightedness, I think I wore them for reading, but I also
remember being told to read at a certain distance and sit a certain
amount away from the TV, which were difficult for me to focus on. These
days my eyes test and perform just as you would expect someone with
classic short sightedness and astigmatism to test.

cheers
Anne