You may want to look into "occupational lens". They are cut with the normal bi/tri focal on the bottom half and a bifocal on the top, leaving the center open for your normal far vision. Most shooters are more comfortable when they tilt their head slightly down/forward in a some what aggressive shooting stance. When you do this, you will be looking more through the top part of your glasses lens.
These occupational lens where originally designed for machine operators who had to read/adjust pressure gauges, or rpm gauges on machine console that were high over head. To prevent the operator from having to adjust their bifocal glasses every time they needed read a gauge, they place another bifocal section in the lens at the top.
Using occupational lens allows you to use the glasses you wear everyday, all day, and in the event you need to use your gun in defense, you are more likely ready, rather than have to hunt around for special glasses you only use at the range.
There is however a catch!! Occupational lens are really weird, especially when you first start wearing them. It takes a while to get use to them, you may have headaches, and some folks just never wear them long enough, giving up on them before they get use to them.
Before I learned how to shoot without glasses, I used the occupational lens on all my corrective glasses. Also, I tried the progressive transitions and they didn't work as well for me as having a distinct line between the far vision and the near bifocal lens at the top.
Hope this helps, or at least gives you an option to consider.
Last edited by EagleSix; 11-24-2011 at 02:47 PM.