Then I'm guessing calebm misremembered what the optometrist said. Probably the optometrist said "your prescription improved" or "your prescription decreased".

"Vision improved" is a possible result of treatment. My wife has had cataract surgery--her vision in that eye certainly improved!

It also is possible to have your vision improve without treatment. I have some astigmatism, it's simply impossible to fully correct. My prescription changes a lot, it's possible for the astigmatism to be a bit less of an issue on a particular exam to the point that the best line I can read sometimes changes.