Since this is the board for scientists and engineers doing important work in optics, I wonder if you guys can help me with a stupid problem. I have a pair of old glasses I really like and don't want to replace. However they have circular lenses, and over time the lenses move imperceptibly until they're out of whack. I don't mind repositioning them (I just rotate them back, then retighten the screw), the problem is that I don't know exactly where to reposition them, because they're perfectly circular. I just have to eyeball it.

This triggers my autism so I am wondering if there is a clever way to bootleg test a glasses lens to see where its "normal" resting place should be. Probably not, but I have a nagging feeling this is one of those problems that some elegantly simple engineering trick would solve. Probably one that costs $4000 and requires a lab but still.

As an added incentive, I am the hot slut in the picture and I will be your gf if you help me figure this out.