I think it mostly has to do with your body getting used to the status quo. Might just take some time at normal levels for your eyes to figure out what's going on. The capillaries in your eyes are some of the most delicate blood vessels in the body, so they can be very sensitive to blood sugar.
When I was first diagnosed (~10 years ago), I spent a week in the hospital coming out of DKA and learning insulin. The week after that my vision went nuts - everything was blurry and I pretty much only had distance vision. It was super scary, and I walked into my fair share of walls before things started to even out and went mostly back to normal. I still need reading glasses now, especially if I've been high a lot recently.