As Duke rightly guessed in another thread, my glasses are bifocals. But since my vision is still unblurred out to about two feet (unless the type in a book is small) I've never mastered the art of reading with them. Nor shooting.
One pair in fact (the newest) gave me a strange kind of double vision during a range visit. I'd just purchased a Ruger LCP, fitted it with a Crimson Trace laser and was eager to try it out. Imaging trying to place a laser when there are two red dots, one above the other. And one target above the other as well.
Went back to the old glasses and the double vision was gone buy my shooting didn't improve that much.
So I opted for a pair of light yellow shooting glasses. My vision is good enough to see the sights without aid and my shooting rapidly improved.
Only downside is that after wearing yellow glasses for a while, you take them off and everything looks blue. Kinda like taking Viagra but with a different kind of fun involved.