Seriously, what the fuck is this?
They can’t legally measure my old old lenses. You know, the ones I tell them work the best?
Yeah, for ‘liability’ reasons, they can’t go by my 6 year old lenses, even though they’re the best I can see through, as a backup monocle…
That’s gotta be the dumbest shit I’ve ever heard.
But sure, I’ll bite. How do you measure the exact curvature of a prescription lens with a tape measure?
Simplest case is you are farsighted. So your lenses are magnifiers. You move them away from a printed page til the magnification is at maximum. The distance to the page is the focal length. Diopter is 1/FL in meters, so eg. 50cm FL is 2.0 diopter. Negative diopters, astigmatism corrections etc are more complicated.
It looks like you can also test your own vision with a phone app and simple device:
Idk anything about that though.
