I had an argument today with one of my customers.
She claims that the ready made readers are made with PD according to the size of the frame. I always thought that they just use the default number for all of them, like 60mm.
Can someone tell me how the OTC are made in terms of PD?
Lenny, Lenny, Lenny...not that's not worth going at it with a pt. Not sure, but if I had to guess, I would say that the OC is put on the Geometric Center of the frame. In any case, what I tell people is that once you start with the +2.00 or higher OTC readers there's a good chance of having strain from prism due to the glasses not being properly centered for their PD.
Only fight with the ones that dont spend $$$!
They are at geo-center for one no need for decentration and two it looks thin!
Most are made at 60 mm, and the ones that aren't are usually 62 mm ( in my experience). Take a handful of them and spot them up. You'll see. Heck, some of them will even have the pd stamped on them, and when I've seen this, it's always been either 60 or 62.
Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA
“As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein
varies. but I've never seen a study concluding PD's could be harmful. I have heard that inappropriate prism is, though.
B
Barry is correct, their not gonna hurt anyone. And if you remember Prentices Rule prism only starts to come into play as the Diopter value goes up, or the PD is significantly off. I just kinda tell people it'll give them eyestrain and let their imagination do the rest. Works for Disney!
I also always thought that it's 60-62.
For most people OTC readers are fine. I have a seen a few people that found having a pair or "real" readers solved whatever thier complaint was with OTC's. And then there is the fact that most people, even those that have had cataracts removed by the great surgeon, have a little cylinder or imballance right to left. Prescription readers can be the answer here.
Chip
As far a induced prism, OTC's usually are 3 diopters or less and one would need quite a bit of decentration to induce enough prism to be a problem, at least for short period reading.
I stole/borrowed 3 pairs from walgreens today. They all measured differently 59 in a bigger frame, 60 in small frame and 62 in medium frame.......
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