I wear bifocals & I find the distance part of my glasses to work best focusing on the ground glass. The viewfinder is optically corrected for distance. As a matter of fact, I find my non bifocal glasses more useful for focusing. Of course I need the bi focals to see the camera settings outside the viewfinder. Fortunately my F2 Photomic & FM2n have f stop & shutter speeds visible in the viewfinder. In addition I have found constantly removing my glasses to use a diopter equipped viewfinder a distraction, so I haven't had to do this yet. Good luck! RO(posted 8334 days ago)