Not sure exactly what you're asking. Do scopes actually make your eyesight worse? NO. If you get used to shooting with scopes for a while, will you have trouble visually picking up the irons if you switch back? In my experience, NO. I shot many thousands of rounds using a scope on my old air rifle in the back yard, and my vision is still better than 20/20.
You might have to re-familiarize yourself to the sight picture with the irons on a particular gun if you've used crosshairs exclusively for a looong time, but it shouldn't take you more than a few shots.
If you need/want a scope, but one and use it, nothing to worry about. I'm thinking about an extended eye relief scope for my Ruger Mk II. I wanna see how the groups hold up beyond 50 yards, just for kicks.