I have a Freezer Baggie of various reading glasses in my shooting gear. I buy them from CVS or similar.
I was taught that you always want the front sight clearly in focus. When we are young, we can rapidly shift focus back and forth to see the target and the front sight clearly. As we age, we have to pick one or the other. Our eyes won't quickly shift any more. Target shooters all say you have to clearly see the front sight to have small groups.
I take a yardstick to measure how far from my eye the front sight is. I then tape a piece of paper with small writing on it to the yardstick at the right distance. Off to the store with the yardstick, and I can pick the pair that best allows me to see the front sight with the least magnification. These reading glasses are like $10.00 or $15.00 for good ones, so no biggie. I have tried $3.00 ones, but the lenses have distortion in them.
These readers work for me. The front sight is clear, and the target a little fuzzy. Longrifles with the sight way out there are a blessing as once the front sight is in focus, the target is less fuzzy than with a pistol.
I use my "cheater" target at the range made of day-glo poster paper. Even when slightly fuzzy, it is really easy to see the aiming point. That shot outside the 50-yard group was the first shot out of the barrel, with the other four clustering nicely. Of course, it could have been the monkey-on-the-crank (me) messing up!
I hope this helps someone a little. God Bless, Marc