You may have superior vision (better than 20/20) which I used to have back in my younger days. Safety glasses always messed with my vision as well. At least the "el cheapos" did. I got with my eye doc and he set me up with some ambers that were fantastic and didn't mess with any part of my vision. He told me the curvature of the glasses in those cheap ones were what affected my vision. Those with superior vision can actually pick up on the focal change while those with average vision just don't pick up on it. I can use the cheapos nowadays without much difference because my old eyes just aint what they used to be. Go to your eye doc MD and have a chat with him about good clear shooting glasses that won't cause any change in your focus.