I have glasses that are actually tri-focal's but are no lines. The last time I bought new glasses I bought a pair with over sized lenses and with a one piece saddle type bridge. When shooting prone I was always looking over the glass which really caused me problems. Same with shooting clays. Can't hit what you can't see you know.
Anyway the once piece bridge makes the glasses ride up higher and at a different angle depending on how you adjust it. When they ground the glass they ground it a bit different and I can see very clearly through the top left hand corner of the glass. This lets me shoot prone and also shoot clays without a problem. Never could get my last pair high enough or clear enough in that spot to shoot decently till this last pair of glasses.
Where I bought my glasses I just told them what I wanted and why and they really worked hard to see that they were made this way and the little gal that did the ordering for me was not a shooter. She just figured out what I wanted and had the lenses made the way I wanted them. Only problem I have had is the nose piece is a soft plastic and in one years time I have had to replace the nose piece 3 times. They also work well as protective glasses too but I will never get glasses again that get as dark as these do. Had a bit of a problem with them being too dark to see clearly through my scope a couple times due to just plain being too dark.