I don't know how it happened but I am an honest case of going from needing glasses (up in the 200 range I think) to 20/20 vision. Started off wearing glasses just to drive, then progressed to wearing them nearly all the time. When we went out to sea though, I wouldn't wear glasses. Why? Because I never needed to see more than 20ft away because you don't wear covers and hence don't salute on aircraft carriers. I found that when we pulled into ports and I had to wear glasses to see who to salute my eyes would always hurt. I figured out that my eyes might be getting better so over then next 7 years I started wearing them less and less till I was down to only wearing them when driving at night. And now I never wear them. Its probably been two to three years since I've worn glasses and I've had my vision checked out to be be 20/20 in that time.