Put the bifocal (near vision) on the top of the lens for proper sight aquisition. I believe it's a must have for those of us who wear bifocals. Check them out here !
SSP Multi Lens Shooting Glasses
When ordering it is the buyer's sole responsibility to order the correct lens diopter. If you order the wrong lens and need to exchange them there will be an additional shipping charge. Here's how to order the correct lenses:
Since typical "readers" are used for reading items closer than the front sight of your pistol, the diopters you use for reading will not be the correct strength for your shooting glasses.
If you hold a full length pencil in your normal shooting grip, the point of the pencil should be sharply focused. It is strongly recommended you try this with several different reader strengths at your local store that sells them. When you find the dopter strength that allows you to see the tip of the pencil at full extension of your arms (where your front sight would be), that is the diopter strength you will need for your shooting glasses. Write that number down, and use it when ordering.
PLEASE CALL IF YOU HAVE ANY QUESTIONS ABOUT DIOPTER CHOICE.