Seems like + Rx's in Shamir Autograph FF Fixed put in a groove mount frame are coming back rather thick. Thicker than I remember them in a GT2. I am using 1.67 index, and polycarb material. Told by lab minimum edge thickness they need is 2.2mm for groove. All things being equal- why would the Zeiss GT2 be thinner than Shamir lens?
HELP!!!!!!! Thanks much.
Marcie Patten:hammer:
Ask the Black Box? I call it a Shamirism; I have always had thickness issues with the Autograph products.
Craig
All things being equal, they shouldn't be. Except that with Shamir's Auto 2 designs, there isn't a lot of room to modify things like thickness and base curve. It could, also be an issue on your lab's end. If you'd like to give me a sample Rx, patient measurements, and frame measurements, I'd be happy to enter the data into our LMS for both an Auto 2 and GT2 and see what, if any, difference I get.
Also, my opinion, 2.2 is thicker than is necessary for groove frames (although that can depend on the frame). I'd say 1.8 (or even 1.5) for Poly and Trivex and no more than 2.0 for everything else. That's what we use here, unless an account specifies something different.
We don't have thickness issues (or at least we don't get complaints about thickness, and believe me, our accounts are always happy to let us know when they aren't happy :) ) on the Shamir lenses and I wonder why others do..... Harry C. can probably give a much more indepth explaination about how the calculations work within the LMS.
There are rules. Knowing those are easy. There are exceptions to the rules. Knowing those are easy. Knowing when to use them is slightly less easy. There are exceptions to the exceptions. Knowing those is a little more tricky, and know when to use those is even more so. Our industry is FULL of all of the above.
They may be optimizing the lens for the Rx, not the cosmetics of the frame. Some labs value optics, some labs value cosmetics, and some labs over value each of those attributes.Originally Posted by Rockstargazer
There you go. It does reduce spoilage, especially important if the freeform manufacturing isn't in-house. That said, you really can't expect an ET too much below 2mm unless you use Trivex, so maybe you can twist the lab managers arm a bit for that extra two or three tenths.
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.
Aargh, yup - Plus Lenses in Shamir - problem after problem after problem - always too thick. We mow use Hoya or Essilor for plus progressives if we want properly thin lenses.
I don't understand all the thickness problems others are having with Shamir lenses. I ran the Rx provided to me by the OP, and yes, the Shamir's were calculated to come out thicker than the GT2's..... by .1mm. Maybe it's just me, but I'll accept .1mm thicker lenses for FreeForm optics.
There are rules. Knowing those are easy. There are exceptions to the rules. Knowing those are easy. Knowing when to use them is slightly less easy. There are exceptions to the exceptions. Knowing those is a little more tricky, and know when to use those is even more so. Our industry is FULL of all of the above.
You don't say whether the lens is a plus or minus, but I will assume a plus. What is your patients RX?
Many Free-form lenses must "stack" the curves on the back. With a grinder all you have on the back is cyl and sphere. With Free-form I not only include the Add, but also the transitional curves that link the add to the distance. Those curves have ratios, those rations stack, and in the end to accomodate all the hundreds curves the lens gets thicker. The second problem is with the add power on the back, the front side base curve will often increase to keep the add from getting too flat. Add into that that most free form lenses require the entire blank to be used for processing, you often can't ground into nothing like you can with a standard process without damaging the equipment. All those combined
will thicken a lens.
The Seiko Surmount shaves a little bit off a plus lens, they patented some previously unused curves and rations (they can combine convave and convex curves on the back) that does result in some thickness savings. They say 25%, but in my experience its about 15%-18% in plus, and about 5%-7% thinner in minus. It may not seem like much, but its the equivalant of 1-2 levels of material changes.
You will notice the issues above in hyperopes more than myopes with higher adds, and higher cyls will also contribute.
You could switch those patients (if they are high plus) to the lifestyle id by hoya...they use both sides of the lens, this should allow you to get the thickness you are looking for
Thank you for your collective expertise and wisdom. Especially thank you to Bill at Rochester Optical for going above and beyond! Bottom line I'm going to revisit Zeiss lenses for my FF. Thanks again!
I want to make sure you understand- the minimum thickness, or the thinnest point of the lens, has everything to do with safety/liability, stability of the surface/optics, and edge design (if the thinnest point is at the edge), and nothing to do with the brand/lens design. If you specify a minimum thickness of 2mm, that's what you'll get (depending on the above, and Z80's ±.3mm tolerance for CT).
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.
Of course I understand the issues of minimum lens thickness but not sure it's as simple as you make it sound. Reading through this thread seems to me the collective wisdom feel Shamir lenses have the potential to be thicker than other brands and it's partially due to design of lens but also affected by how a lab chooses to "optimize" the lens manufacturing. Some prefer cosmetics some prefer optics. Did I miss something?
All I know is shamir lenses when compared to my go to PAL for years, Zeiss GT2 are thicker in moderate to low plus Rx's.
It is. Minimum thickness is essentially a constant, assuming the same material and edge design.
Maximum and average thickness is a much more complicated issue, and is related to surface design and placement of the progressive optics. In general, aspheric back surface PALs (Auto) will be thicker in plus powers with higher adds than front surface aspheric PALs (GT2).Reading through this thread seems to me the collective wisdom feel Shamir lenses have the potential to be thicker than other brands and it's partially due to design of lens but also affected by how a lab chooses to "optimize" the lens manufacturing. Some prefer cosmetics some prefer optics. Did I miss something?
All I know is shamir lenses when compared to my go to PAL for years, Zeiss GT2 are thicker in moderate to low plus Rx's.
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.
In theory, yes, minimum thickness is going to be pretty uniform but what I think is happening, and what I've noticed myself, is that due to the manufacturing process of the autograph line, plus lenses have excess thickness. I've got a guy that I just got back with a +1.75 -1.00 @ 90 that looks absolutely hideous. The edge thickness is about 3 mm on it, and that seems to be the norm with autograph. I'm at the point now that I'm going to do hoya for anything plus and reserve shamir for minus.
We just rejected a few pair of Shamir plus lenses for excessive thickness; they are the only one we have a thickness issue with and soon we will no longer have to use them!!
Don't get me wrong, I love the autograph II, just am realizing that it's not that great for plus patients. From here on, I'm just doing what I always do and select the best lens available for each individual patient. Sometimes it's an Id Instyle, sometimes Autograph II, but I can definitely say that I have trimmed down my suggested area for the autograph lenses.
I'm consistently receiving a 1.8mm to 2mm ET for drill mounts, including Autograph 2's. Talk to Norb Tausch at Soderberg Oak Creek Wi.
Sometimes it's less profitable, with a few more headaches, but your integrity and reputation follows you. Bravo.
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.
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