I've had bifocals for about 6 years now. I can't shoot any long gun without a scope since I got them. I can't focus the front and rear sights together. I'm sure it didn't help that I've had cataract surgery on both eyes. They put plastic implants in my eyes and I have better than 20/20 vision for distance but need bifocals for reading. You really loose the ability to focus when you have those implants. A buddy of mine said I may have to go to a tri focal. I have the same issues with handguns too.