I have to use bi-focal safety glasses in the 2.5-3.0 diopter range. I have not yet found a pair that doesn't distort the magnified area so bad, they really just give you a headache. Cheap manufacture I'm sure is the culprit. Does anyone have any recommendations for bi-focal safety glassed that are higher quality? Most the less than 20 dollars kind, are so curved that this ads to the distortion.