I graduated from OCS in February '03 and right now I am going through primary flight training with the Navy.
It used to be that you had to have 20/20 vision to become a pilot for the military. Now I think that the cutoff is 20/50 correctable to 20/20 with glasses.
If your' vision is really poor (worse than 20/50), you can get a medical waiver if you have your vision corrected with PRK surgery to 20/20. I think that is the only eye surgery that the Navy will allow. As for the other branches, I have no idea.
Ofcourse, you can always sign up to become a Flight Officer. They have no vision requirements. You won't be at the controls, but you'll still be able to fly.
Hope this helps.