First off, I am an ABO certified optician. What seems to work the best for pistol shooting for most people is single vision lenses with your distance prescription in your non-dominant eye and your intermediate prescription in your dominant eye. This allows you to shoot with both eyes open and see the front sight and the target clearly. Your intermediate prescription is half of your reading add, the smallest section on the top of your trifocal segment. If you ask any optician or optometrist who's worth his salt, he can convert your current Rx to intermediate only with a few simple algebraic calculations. Single vision lenses also cost considerably less than trifocals, too. Fortunately, I'm young enough to not need them yet. If you're getting a pair of glasses just for shooting, you might consider doing what I did and getting a pair of wraparound shooting glasses with an Rx insert. With the ones I have, I can switch the insert from a yellow-lens pair to a pair with polarized sun lenses depending on conditions, and it offers more coverage and protection than my regular glasses.