I just posted this within another thread, but I though it might be helpful as a stand-alone too.
For those who have eyes that are getting worse, here is a tip. Go to your local store with a yard stick or meter stick. Find the section with reading glasses. Try on glasses until you can see the end of stick clearly. Buy the ones with the lowest magnification that allow you to see the end clearly. I have a baggie full of reading glasses I take when I go shooting (they don't cost much) . I can handle just about any length barrel that way, from short handguns to longrifles. The longrifles need the lowest magnification, and are the easiest to shoot well. Yes, the target is a little fuzzy, but isn't that what instructors say is correct anyway? Don't give up on good shooting! This works for me and I hope it helps others.
God Bless, Marc