Depends on the lab. I would hope and assume labs are only using top end designs with Camber blanks.
Cherry has IOT's Camber Steady in the same (top) price tier as Varilux S/X, so no difference there. US Optical's CamberHD is cheaper than alot of their Varilux lines, I'll give you that (gives me slight pause on the quality of the design to be honest). Several others are significantly higher.
Originally Posted by Elvis Is Alive
It's not like they can take a Camber blank and slap any old lens design on it. A Camber Steady from one lab is going to be the same as Camber Steady from any other lab. They all have to pass the same certifications with IOT to produce the lens designs.
I know, which is bonkers if you ask me. (PM me if you want to discuss more on IOT lens price.)
Depends on their history- Rx, BC/thickness, material, etc. I've used Multigressiv, Varilux, Definity, Ind. 2I, etc.
Robert
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
OK, to update this thread and cross-reference it, Essilor designs are front surface progressives. https://www.optiboard.com/forums/sho...ace#post574303
Might be a regional/geographic variation in product availability, but as far as my local reps tell me, Essilor/Nikon lenses in Southeast Asia all have the progressive optics on the back surface, with spherical front surfaces (except for the Varilux X and formerly, S series).
The apparent proof to their claim is when we verify the near Rx of received lenses, the addition is often weaker than even the compensated Rx provided for verification... they tell us to flip the lens such that the front surface will face the lens meter stop, and then to verify the near Rx. This explained to me as being possible since the progressive optics being on the back may encroach within the aperture of the lens meter stop, and therefore affect the reading.
So far, it's worked out as claimed, and they've been good with remakes for those which did not pass verification even that way.
I think that's the way to verify any front surface multifocal, even segmented. Right? Not that anyone does that. I don't think that's proof.
The reason you turn a segmented lens around to check the power of the add is this eliminates the thickness of the lens which adds plus power to the seg. When you do this you must read the distance as well as the seg reversed and the difference is the power of the seg. The explanation from Andy makes no sense to me.
For segmented multifocals I'd agree, that's also how I was taught to verify them, convex side facing down. Reading distance and near Rx separately, then deducting the difference to get the add.
The lenses being discussed here are progressives, however, and not segmented multifocals.
For progressives, be it manual or digital lens meters, with the old front surface designs I never saw issues verifying the add even with the concave side facing downwards towards the lens meter stop. The distance and near Rx consistently could be verified as such, even if the method was wrong.
When everyone started moving progressive optics to the back surface, the add often read weaker than even the compensated/recalculated/etc modified Rx the labs provided for verification.
Explanation given by the labs was that it was not a production defect. So we were told to flip the lens and verify the back surface progressive as if it was a segmented multifocal, for the reason as described in my first post.
Doing so yielded verified Rx within tolerances, and wearers had good vision + feedback with the lenses on dispense, therefore I left it at that.
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