OK, here's what I need to know: how far off is my lens clock, which is labeled in diopters of curvature for crown glass (n = 1.523 IIRC)?
I know that it's accurate enough for CR39 (n = 1.4985).
Therefore it should be accurate enough for polycarbonate (n = 1.59), right?
I mean, it's off a weensy, but it should be under even a 1/2 D, right?
I NEED TO KNOW!!!!
Why, do you ask?
I have an impatient who was getting replacement poly -1.00 FT 28 lenses for an old frame that we sold him (no major change in Rx).
The old frame is one of those jobbies where it's semi-rimless on the bottom, and the upper metal eyewire is a thin metal that sits in the groove (Emporio Armani...tre chic. Whatevs.)
The original lens base curve measures +3.0
His new lenses measure +3.0 (by our lens clock).
They were dispensed OTC to his wife, just cause.
Weeks later, his life is not worth living and complains of "everything is distorted/I'm in a fishbowl" or whatever. I measure the temporary EVEN OLDER glasses that he's been wearing until the job got done, and it was a +4.50 base. So, I assume that he's adapted to his old, old base curve and isn't patient enough to re-adapt to the original base curve in which he had heretofore been living a happy existence.
Now, I could tell him to suck it up, he must have "de-adapted" to the +3.0 while we was wearing the +4.5, give it time, but again, the world is ending, so I decide to remake the new lenses to match what he's temporarily wearing.
So I send it back to the baL PSV (use a mirror to decode that) and request a +4.50 base curve or anything remotely close. They keep sending me +3.0 base! Again and again! They swear they enter +4.0 base when we call. But it always reads +3.0 to us.
Now I understand that maybe there can be some computer overriding the entry because of the goofy frame front, and possibly flatter is better for glazing?
But why the discrepancy in what the lab says and what we measure?
Bookmarks