Essilor 1.74 FFSV lens design

[T.Webber]

OK, here is my question. I have had a few people tell me now that the 1.74 lens will not read properly on a regular lensometer that the power will not read what the Rx is given to the lab. A friend who works for Essilor told me that there is a conversion chart for this lens. So hoping someone with experience with this lens will solve my problem or at least give some insight.

John Q. Public
Has a given Rx of, SV-DVO

O.D. -13.50 -1.25 X 068
O.S. -14.25 -1.50 X 128

This job reads on a Marco Lensometer

O.D. -14.00 -1.25 X 059
O.S. -14.25 -1.50 X 119
1.25 VI @ the O.C.

Tell me if I am wrong but this is the second remake that the lab has sent me. First it was just transposed wrong and they got both lenses off 90 degrees.
In further inspection, I am just reading the power of the lens as normal on the Lenosmeter.

I have been and Optician for longer than i want to admit but I would just say that the lab just got it wrong again.
I hear from essilor that the lab should have sent me the conversion for this power along with the lab invoice.

So Is there a conversion chart or what?
Any and all help is appreciated.

Thank you,
Best Regards:

T-ford Webber
Licensed Optician/VA

[snowmonster]

A bit odd in that the OS lens is spot on as far as sphere power goes but the OD lens is off by 0.50 D. Could it be possible that you're reading lens power outside of the optical zone, giving you weird power and axis readings?

[DragonLensmanWV]

I duuno about any conversion chart but there's simply toooo much variance between lenses there for them to be accepted. We assume you're reading them at OC since with that Rx, anything very far off center will be unreadable.I know, that's very near my Rx.
10 degrees off on a 1.50 cyl is the closest they can get? Find a new lab for that.
And switch them to 1.70, the higher ABBE will be appreciated at small gain in thickness.

[Craig]

OK, here is my question. I have had a few people tell me now that the 1.74 lens will not read properly on a regular lensometer that the power will not read what the Rx is given to the lab. A friend who works for Essilor told me that there is a conversion chart for this lens. So hoping someone with experience with this lens will solve my problem or at least give some insight.

John Q. Public
Has a given Rx of, SV-DVO

O.D. -13.50 -1.25 X 068
O.S. -14.25 -1.50 X 128

This job reads on a Marco Lensometer

O.D. -14.00 -1.25 X 059
O.S. -14.25 -1.50 X 119
1.25 VI @ the O.C.

Tell me if I am wrong but this is the second remake that the lab has sent me. First it was just transposed wrong and they got both lenses off 90 degrees.
In further inspection, I am just reading the power of the lens as normal on the Lenosmeter.

I have been and Optician for longer than i want to admit but I would just say that the lab just got it wrong again.
I hear from essilor that the lab should have sent me the conversion for this power along with the lab invoice.

So Is there a conversion chart or what?
Any and all help is appreciated.

Thank you,
Best Regards:

T-ford Webber
Licensed Optician/VA

Sounds like Essilor made a mistake again.
The problem is the lens is only made by one facility and I thought they should check the power before shipping.

I suggest a 1.70 from Pech Optical, I use it rather than the 1.74 for the lower cost and the ability to get an accurate RX in a few days. The thickness difference between the 2 indexes is almost nothing.

BEst of Luck!

Craig
TEchnology Broker

[EyeFitWell]

I ran into the same claims shortly after 1.74 came out. I can understand that if I measured the curves and thickness and calculated power that way (the equation set up for 1.53), I'd get it off. But doesn't the lensometer actually read effective power??

[Jaltman]

I agree...I don't trust essilors tech support. Just recently i made a pair of super modular asherics and because I didn't have the tooling chart in my books I had them calc it for me using my measurements and they were off by .75D and they finally tracked down a paper version of the tooling chart for me and sure enough they were wrong. I modified the tooling and it worked out fine.