Being a Plumber/Pipefitter and working for the Dept Of Defense, they furnished us with safety glasses. Since a lot of my work was overhead, I got those glasses with the bifocal on top and bottom. They sure came in handy for some things, like when I am hunting and need to wear my glasses, then shoot. Normally I just take my glasses off to shoot. I'm fortunate my eyesight is not that bad, and I can get along without my glasses. I am in the same perscription that I started with back in 1978 when I started wearing glasses. My bi-focal is just a clear lens with no correction.