I’ve worn single vision prescription eyeglasses for nearsightedness for many years, but can’t comfortably read or see close-up with them on any more - I posted here a few months back asking for opinions about bifocal/progressive glasses (link).
Last week I finally went in and got an exam, and am wondering about how the “Add” value for the lower part of the lens works - if my distance correction is -3.50 with an “Add” of +1.75, what will be the actual correction I’ll be looking through in the lower part of the lens?
-1.75 seems logical (-3.50+1.75) but that doesn’t seem right - I don’t think I need/want negative correction to read?
+1.75 certainly doesn’t seem correct - off-the-shelf +1.75 reading glasses would be much too strong for me I think…
As I read without glasses at all now, I’m thinking something close to no correction at all in the bottom portion of the lens would be ideal, but perhaps I’m mistaken? - Anyway, I’ve ordered a pair from Zenni (who I’ve been using for years) to try, I’m just wondering how these numbers work.
I think your “what seems logical” is the right one. -1.75 is not very strong. Probably right now when reading with no glasses you’re holding things quite close to your face.
Yes I do actually, especially if the text is small - I see, so a weak negative prescription might allow me to read that same text at a more normal (bent arm’s length) distance.
“What seems logical” is the correct answer. My prescription is at -10.0, and so my bi-focals would be -10 with an add of 2.
If I take off my glasses, I can only read something that is about 2 inches from my nose. If I put on glasses that are at -8, I would not be able to read road signes, but something that is 18 inches in front of me would be legible.
In actuality, I wear contact lenses that give me the correction I need, and just put +2 reading glasses on when I need to read. Yes, it does sound silly to put glasses on over contacts, but it works.
Some folks will put different strengh lenses for each eye. For my case, that might mean -10 in my left eye, and -8 in my right. Then I would use the left eye for distance, and right eye for reading. I have decided (for now) to just go with the reading glasses, though.
Thanks for the reply! - my mistake was that I’ve always associated “reading glasses” with positive correction…it’s starting to make sense to me now that what I actually need for reading is less negative correction than I need for distance (a “relative” positive correction, you might say.)