Variable Seg Lenses - fitting implications etc...

[Uilleann]

For those of you in a practice/dispensary that are doing a lot of variable seg design progressives, I'm curious if you are noticing any unique fitting challenges as compared against a set height lens design. For example, if you have a patient who chooses two very different B frames (let's just say one is clear the other a sun for the sake of this question), the clear pair , a narrow B, you measure the seg at 14 or so. The sunnies, being much larger in B, you end up with a 23.

Now most other things being equal, such as material, base curve and the like, are you seeing any non-adapt issues, or complaints regarding overall clarity or peripheral astigmatism more noticeable in one pair vs. the other? Assuming the lens is the same design, the difference in the seg could, in essence, make both lenses perform rather differently, optically for the patient correct?

Would this difference be noticeable to the average patient in your experiences? Are you routinely tracking the segs of the variable lenses you're dispensing (I would assume so in the normal course of the order yes?) How are you able to determine the proper heights of variable seg lenses you have NOT made yourself?

Just idle thoughts this morning. Thanks for any and all experience you can share. :cheers::cheers::cheers:

[YrahG]

Which variable design are you referring too?

[Uilleann]

Well, ANY of the variable seg designs that are being used. There are a number out there I am aware. I'm not so much concerned with a particular name brand, as I am with the general implications that may (or indeed may not) arise from the fitting of a given design with a variable seg. Particularly as it may pertain to multiple pairs for a single patient, in different frame designs.

[YrahG]

Well, ANY of the variable seg designs that are being used. There are a number out there I am aware. I'm not so much concerned with a particular name brand, as I am with the general implications that may (or indeed may not) arise from the fitting of a given design with a variable seg. Particularly as it may pertain to multiple pairs for a single patient, in different frame designs.

I get the feeling this is a loaded question. How do your patients do with a Physio sun and Physio Short day to day pair?

[HarryChiling]

For those of you in a practice/dispensary that are doing a lot of variable seg design progressives, I'm curious if you are noticing any unique fitting challenges as compared against a set height lens design. For example, if you have a patient who chooses two very different B frames (let's just say one is clear the other a sun for the sake of this question), the clear pair , a narrow B, you measure the seg at 14 or so. The sunnies, being much larger in B, you end up with a 23.

Now most other things being equal, such as material, base curve and the like, are you seeing any non-adapt issues, or complaints regarding overall clarity or peripheral astigmatism more noticeable in one pair vs. the other? Assuming the lens is the same design, the difference in the seg could, in essence, make both lenses perform rather differently, optically for the patient correct?

Would this difference be noticeable to the average patient in your experiences? Are you routinely tracking the segs of the variable lenses you're dispensing (I would assume so in the normal course of the order yes?) How are you able to determine the proper heights of variable seg lenses you have NOT made yourself?

Just idle thoughts this morning. Thanks for any and all experience you can share. :cheers::cheers::cheers:

I always preferred to stay within the same design or manufacturer for multiple pairs. The design goals will remain the same within the same manufacturers products allowing more consistency between pairs and from what I have seen an easier adaption. Of course it's always good to prep your patient for the differences, and initially I like to point those things out in the fitting stage letting them know that the differences in the frame will change the designs available. As a side note I usually fit higher adds with a fixed design to make sure that the near portion was adequate, but anything under a +2.00 was fair game for a variable design.

[WFruit]

For those of you in a practice/dispensary that are doing a lot of variable seg design progressives, I'm curious if you are noticing any unique fitting challenges as compared against a set height lens design. For example, if you have a patient who chooses two very different B frames (let's just say one is clear the other a sun for the sake of this question), the clear pair , a narrow B, you measure the seg at 14 or so. The sunnies, being much larger in B, you end up with a 23.

Now most other things being equal, such as material, base curve and the like, are you seeing any non-adapt issues, or complaints regarding overall clarity or peripheral astigmatism more noticeable in one pair vs. the other? A larger lens progressive will always have a larger area of distortion vs. a smaller lens. The advantage to the Free Form lenses is that the clear viewing areas are so much larger, and the area of peripheral astigmatic distortion is "softer." Is it noticable? Yes, absolutely. But it isn't as bothersome as it is in molded progressive. Assuming the lens is the same design, the difference in the seg could, in essence, make both lenses perform rather differently, optically for the patient correct? Well, sort of. The big difference is that the shorter the corridor in a Free Form lens, the "harder" the design becomes. While the peripheral distortion is smaller in a smaller lens, in the shorter corridors it's more noticeable.

Would this difference be noticeable to the average patient in your experiences? Are you routinely tracking the segs of the variable lenses you're dispensing (I would assume so in the normal course of the order yes?) How are you able to determine the proper heights of variable seg lenses you have NOT made yourself? Since it's the corrider length that changes, and not where the distance is placed, the seg ht should be the same, whether it's an variable or fixed seg ht. So it's determining the corridor length that becomes the challenge. The fixed designs have their heights engraved on the lens under the progressive marking, the variable design does not, so identifying that part is easy.

Just idle thoughts this morning. Thanks for any and all experience you can share. :cheers::cheers::cheers:

I can give you the perspective of a lab and what we see in and from our retail stores, based on the Shamir Autograph II Variable vs. Shamir Autograph II Fixed.

What you're really looking for is the perspective of FIRST TIME progressive wearers in this situation. Most people who have a smaller clear frame and larger sunglasses (keeping with your example) who have been wearing them for a while are used to the different corridor lengths.

As far as remakes, we've seen very few for the Variable, although hyperopes tend to have more trouble with it than myopes. This seems to stem more from the Rx compensation done by Shamir's software than anything else.

Since the Fixed designs come in 11, 13, 15, and 18 seg hts, the Variable is usually better for the odder frame shapes, such as teardrop aviator styles, since a near PD can also be specified to ensure that there is a full reading area within the lens. Yes, this changes not only the corridor lenght, but it's "shape" as well. (If you're going to ask if this means that you can have a progressive with a corridor that diverges rather than converges, the answer is yes, but you have to yell at the software a lot to do it.)

There is a maximum height that the Variable can be "streched" to as well. I believe it's ~20mm. Perhapse one of our Shamir people here can clarify that.

[Uilleann]

I get the feeling this is a loaded question. How do your patients do with a Physio sun and Physio Short day to day pair?

As these are different lens designs and neither would be variable heights as far as I know (I'm unaware of any lens called "Physio Sun" for that matter), that wasn't what my question pertained to anyway. I'm not interested in getting into the OB rut of brand bashing Essilor, or any manufacturer for that matter here. Just looking for honest discussion from those with direct experience in fitting variable seg designs.


@ Harry
Yes, I agree. Keep everything as similar as one possibly can, and you generally will minimize the chance for some nasty little variable causing a non-adapt issue. That's actually pointing to the root of my original post. All other things being generally equal, the difference in seg of a variable seg style lens, in two different frames for the same patient - are we looking at potential problems from a patient perspective? In the patient's mind, the two pairs of glasses were made to the exact same prescription. And we've further told them that the new digitally surfaced/designed lens will be more accurate than anything before. Yet - will they notice a difference (and perhaps have a preference) between the two pairs due to the different seg heights dispensed?

I further agree that proper education and patient understanding is key - period. With ANY lens or lens feature. I just wonder if this opens up a new potential for non-adapts that may not have existed before?


@ WFruit
Great info! Thank you for that. I wish I could tell you that ALL of our patients were first timers...but being both close to a University/Med school, and a downtown urban center with loads of accountants, lawyers, day traders and the like, we also see a large transient patient base, and a good number of first time patients will also be long time progressive wearers. Adding to that mix, as we are downtown urban, there are also a number who have gone the cheaper chain store route, only to find complete dissatisfaction with their glasses. Our job is then of course to not only fix the problem, but to provide an outstanding visual solution for them, consistent with their (reasonable) expectations.

Now, in our office, none of our fixed designs have the seg etched into the lens. You state that yours do? And that the variable designs would not? Was that a typo which should have just been reversed? Or is that truly what you see?

Appreciate all the insight guys! Thank you! :cheers::cheers::cheers:

Bri~

[WFruit]

Now, in our office, none of our fixed designs have the seg etched into the lens. You state that yours do? And that the variable designs would not? Was that a typo which should have just been reversed? Or is that truly what you see?

Appreciate all the insight guys! Thank you! :cheers::cheers::cheers:

Bri~

It is not a typo, it's standard for the Shamir Autograph II line. The Fixed designes have their seg ht etched, and the Variable design does not. (See the FreeForm part of this chart from Shamir for what their engravings look like http://www.shamirlens.com/images/quick_ref.pdf)

I don't know enough about our laser engraver, but I'm willing to bet that someone, somewhere could program it to etch the exact seg ht for the Variable lens. However, the fitting cross for the Autograph II line, Variable included, is 4 above the 180 line, so you can always tell what the seg ht is, just not what the corridor length is. And with the absence of the engraved height, you always know that you have a Variable. In theory, a Variable progressive going into frames with the same B measurement and similar shape should have the same, or very close, corridor length.

[Mr. Finney]

In my experience, the variable designs don't work as well as I can make a fixed design work. Maybe that goes to the "lifestyle dispensing" thing. I always find out what general activities and habits the patient has so I can choose what I think will be the proper seg placement, corridor length, etc.

[Robert Martellaro]

Assuming the lens is the same design, the difference in the seg could, in essence, make both lenses perform rather differently, optically for the patient correct?

Correct.

Would this difference be noticeable to the average patient in your experiences?

Sure, especially with higher Adds and large disparities in corridor lengths, or in this case the "B" dimension. Some will grin and bear it- "I guess that's the way it has to be", some might not notice, some will complain, others might not come back at all, ever.

For example, my present frame has a 30mm B, with a 20mm fitting height. I tried a highly respected, excellent quality, variable freeform PAL and found the near vision wanting- I had to lift my chin to see small text clearly, and was constantly raising my chin to read the paper at the dinner table. It was a variable design, and the software defaulted to longest corridor. There was no way to specify the corridor length, so the only way to get the near performance I desire is to choose a narrower frame, which would put the bottom of the lens and/or frame right in the middle of the bottom of the page. No thanks.

Another scenario is an advanced presbyopic moderate myope who takes off their glasses when reading, chooses a frame with a 25mm B, but wants the best possible on and off-axis distance vision, with good intermediate for the automobile, with some near utility. The software now chooses a very short corridor, resulting in compromised (for some) distance night vision, blurred off-axis distance vision, and a very dynamic and "busy" lens. It's not what the wearer wants or needs, and they paid dearly for a lens that under performs. A Sola VIP would've offered better distance performance at one third the price.

IMO, the variable designs are for the trainees and/or busy, insurance driven dispensaries that don't have the skills or the time to do it right.

[Mr. Finney]

Well said Robert!

[Uilleann]

Robert,

That is precisely what I was wondering about. Thank you!! I understand that the likelihood of most patients having a non-adapt problem with a variable seg (and I apologize, I should have used the more correct term "variable corridor" before...thanks for getting what I meant all the same!) is small. But I also know that for every optical action, there can be an opposite reaction. In this case, a variable length design offers "greater frame fit" but at the potential cost of a predictable visual outcome in a given lens.

I think it's very important for dispensers to be aware and understand the implications of frame selection on a lens design. In my own personal experience, I believe this is one of the greatest areas new/under-trained staff fail miserably. I tend to be rather picky about matching the frame to the lens, and if it can ever be helped - never doing it the other way around. Variable corridor lenses actually seem to complicate this slightly from a predictable optics standpoint - hence my original post.

I sincerely appreciate all the insight and information provided so far. Please feel free to continue if there is more anyone wishes to add!!

All the very best!

And in honor of St. Pat's next week - Sláinte!!!

:cheers::cheers::cheers::cheers::cheers:

Bri~

[OCP]

Quite interesting thread and time will tell us how to solve this issue best possible.
A rule of thumb is, if you have more than 5 mm difference between two pairs of progressive, you can get in trouble.
Less than 5 mm, it will usual not give any troubles.

[WFruit]

Correct.


Sure, especially with higher Adds and large disparities in corridor lengths, or in this case the "B" dimension. Some will grin and bear it- "I guess that's the way it has to be", some might not notice, some will complain, others might not come back at all, ever.

For example, my present frame has a 30mm B, with a 20mm fitting height. I tried a highly respected, excellent quality, variable freeform PAL and found the near vision wanting- I had to lift my chin to see small text clearly, and was constantly raising my chin to read the paper at the dinner table. It was a variable design, and the software defaulted to longest corridor. There was no way to specify the corridor length, so the only way to get the near performance I desire is to choose a narrower frame, which would put the bottom of the lens and/or frame right in the middle of the bottom of the page. No thanks. My question here would be, why go with the variable design? At that height, with that B dimension, it would be unecesary; the fixed height 18 would have served you better. On the other hand, the software should not have defaulted to the longest corridor, that may be a software issue on the lab's end.

Another scenario is an advanced presbyopic moderate myope who takes off their glasses when reading, chooses a frame with a 25mm B, but wants the best possible on and off-axis distance vision, with good intermediate for the automobile, with some near utility. The software now chooses a very short corridor, resulting in compromised (for some) distance night vision, blurred off-axis distance vision, and a very dynamic and "busy" lens. It's not what the wearer wants or needs, and they paid dearly for a lens that under performs. A Sola VIP would've offered better distance performance at one third the price. The software would only choose a very short corridor if the seg ht demanded it, for example if the seg were at 11.... in which case the fixed ht 11 would have the same issues. A better result might be to order a higher seg ht fixed, say 13 and edged the lens lower. A VIP would only provide better performance if the seg ht were much higher, say 18~20... in which case the software wouldn't default to the shortest corridor length for the Variable design.

IMO, the variable designs are for the trainees and/or busy, insurance driven dispensaries that don't have the skills or the time to do it right. Given the complexities of insuring proper fit with the Variable, I would say that it is absolutely NOT for trainees, nor for offices that "don't have the skills."

First note: In my lab we deal with the Shamir Autograph II Variable lens, so that's my point of reference in discussing variable fitting height progressives. I don't work for Shamir, nor have any relationship with them, other than we use their progressive designs (we use Seiko Free Form as well, but they do not have a variable height progressive).

When calculating the corridor lenght on a Variable, the software does not look exclusively at the B measurment for the frame. It looks at requested seg ht, B measurement, and frame shape (a rectangular 25 B frame will have different progressive space than an oval 25 B frame, even if the PD and Seg ht are the same for both pairs). In the oval frame the Variable would be more necessary, since the software will insure that there is enough reading space.

[Robert Martellaro]

My question here would be, why go with the variable design?

I was evaluating the design just as I evaulate almost all the lenses I use for my clients. I will not use this lens for avid readers in Adds above +1.75.

The software would only choose a very short corridor if the seg ht demanded it

But in the example I gave above, the situation demands a longer corridor for better distance vision. The software doesn't know this of course, so it uses a short corridor. My point is that the optician sometimes need to override to software, and where this is not possible (which was true with the lens I tried above) use a different PAL design.

First note: In my lab we deal with the Shamir Autograph II Variable lens, so that's my point of reference in discussing variable fitting height progressives.

You might want to become more familar with their fixed designs. Let's say I have a client wearing a Piccolo or Ellipse at 19mm. If you use an Auto 2 variable, the software will use the longest corridor (about 13mm to full Add power). There's a good chance that the client will complain about having to lift their chin to see the monitor and small text, and they'll really be upset that it cost them $100 to $150 more for a PAL that gives them a sore neck and probably a headache!

When calculating the corridor lenght on a Variable, the software does not look exclusively at the B measurment for the frame. It looks at requested seg ht, B measurement, and frame shape (a rectangular 25 B frame will have different progressive space than an oval 25 B frame, even if the PD and Seg ht are the same for both pairs). In the oval frame the Variable would be more necessary, since the software will insure that there is enough reading space.

It wouldn't make it necessary to use a variable corridor, but would usually (but not always- note my example above) require a shorter corridor. That might be an Auto 2 fixed 15mm or 13mm, a Rodenstock Impression ILT XS, etc. The variable makes sense for those who don't pay attention to the frame shape- the difference between the measured seg height and the usable seg height, and don't feel comfortable with the fixed designs for some reason.

[WFruit]

I was evaluating the design just as I evaulate almost all the lenses I use for my clients. I will not use this lens for avid readers in Adds above +1.75.



But in the example I gave above, the situation demands a longer corridor for better distance vision. The software doesn't know this of course, so it uses a short corridor. My point is that the optician sometimes need to override to software, and where this is not possible (which was true with the lens I tried above) use a different PAL design.

You might want to become more familar with their fixed designs. Let's say I have a client wearing a Piccolo or Ellipse at 19mm. If you use an Auto 2 variable, the software will use the longest corridor (about 13mm to full Add power). There's a good chance that the client will complain about having to lift their chin to see the monitor and small text, and they'll really be upset that it cost them $100 to $150 more for a PAL that gives them a sore neck and probably a headache! I am completely familiar with all of Shamir's lenses that are currently available in the US. My point was that the only variable design lens that I am familiar with is Shamir's. I cannot speak about any other lens manufacturer's variable designs because we do not use them.

It wouldn't make it necessary to use a variable corridor, but would usually (but not always- note my example above) require a shorter corridor. That might be an Auto 2 fixed 15mm or 13mm, a Rodenstock Impression ILT XS, etc. The variable makes sense for those who don't pay attention to the frame shape- the difference between the measured seg height and the usable seg height, and don't feel comfortable with the fixed designs for some reason.

The Variable corridor length design lens is NOT a general purpose, catch all lens, which I think too many people try to make it be. It's designed to be used in very specific circumstances where a fixed height lens would lose to much reading area due to frame shape constraints.

[Uilleann]

Which is frustrating for those of us who DO in fact look at the frame as it relates to supporting the function of the lens - as opposed to what so many un/under-trained "dispensers" do. Meaning they Pick a frame shape and size based on color alone...or how many rhinestones that 'pretty' style has over there...never mind that it's a 23 B.

It feels as though these variable designs are trying to be "smarter" than the optician fitting them. It appears to be adding an extra level of complexity and more importantly variability with what would otherwise be the "same" lens. *sigh*

[WFruit]

Well.....

The lenses themselves are quite simple. I think it's the marketing departments that are trying to be smarter than the opticians.

In our lab, there have been cases where the Variable lens was ordered and it was not the optimal lens for the job. A fixed design would work better. In these cases we call the account and explain. Now, I am aware that there are some opticians who would be offended (and to some extent, rightly so) at a lab dicating what lens they should use (except that these same opticians will only use Essilor labs, who of course NEVER dictate what lenses you can buy from them....). However, even more opticians and doctors have been happy that we care enough to call and explain the lens, and help them understand how it works and when it should be used.

Variable length progressives are a very good idea, and a very useful lens IF they are properly understood and ordered appropriately. If used as a general purpose lens, they can and WILL cause issues. As with almost everything in optics and dispensing, education is the key.

[barryh66]

In my experience, the variable designs don't work as well as I can make a fixed design work. Maybe that goes to the "lifestyle dispensing" thing. I always find out what general activities and habits the patient has so I can choose what I think will be the proper seg placement, corridor length, etc.

If you are refering to the AutoII, shamir rep just left me a new fitting guide. After I have fit several hundred and where them in several of my gl's I didn't know the design varied as much as it does. I have only used variable on my gl's and find adaption between b's not an issue but I will have to try the fixed design to compare the difference.

[SailorEd]

Would this difference be noticeable to the average patient in your experiences? Are you routinely tracking the segs of the variable lenses you're dispensing (I would assume so in the normal course of the order yes?) How are you able to determine the proper heights of variable seg lenses you have NOT made yourself?

:cheers::cheers::cheers:

I do about 75% in the Varilux Ellipse (soon to become the Physio Short) and about another 20% in the Physio. For my sunglasses (Polarized), I always use the Younger Image. Never have had a problem. Person in the Ellipse with a 16 Seg and in the Image with a 22 seg. Not a problem.

[Uilleann]

Ed,

The Ellipse, Physio Short (different from the Ellipse actually), standard Physio and Image are all fixed corridor designs. My question wasn't looking to compare those designs as such. But rather to explore the potential difference in the SAME lens style, assuming it uses a variable corridor algorithm when it's produced, with the same Rx, in different B sized frames - and therefore different segs and lens designs.

[Mr. Finney]

Getting back to your original question, I would think you would have the same reaction from patients in, say, Auto 2 Variables, as you would in, say, Auto 2 Fixed 13 (in the smaller B frame) and Auto 2 18 (in the deeper frame). Obviously the wearer's visual perception would differ from one pair to the other, but some people accomodate this difference very easily, while some don't.

As for adaptation issues, I can't really add much there, as I rarely order variable designs. In fact, I quit ordering Uniques long ago, and I steer clear of the other variable designs, because of the less than stellar success with the Unique. BUT, I can't necessarily blame it on the variable design; maybe it was the design of the Unique that folks didn't like? Either way, I just decided I would rather have control of corridor length and near power placement.

As for determining the seg height, or near location, on lenses made elsewhere, again I can't say with a lot of accuarcy here, but I think most of the manufacturers put a corridor length identifier on the lens, under the add. Maybe that's just on the Unique, but it seems like I've seen it on others too.

Hope I didn't muddy the waters any!

[Uilleann]

Nope Bry, you nailed it. And your fixed design (standard vs. short corridor) makes a perfect point. It's basically the same situation, but you have some small sense of what you're getting. With the variables, it just seems like a lot more is left up to chance with the final design outcome. :)

[Mr. Finney]

I agree, but that could just be because I'm not one of these "engineer" opticians! :))

[HarryChiling]

The variable can be a good fit when applied properly. I have an illustration that will allow you to see the best scenario for fitting a variable design. I prefer to use a cut out chart, but as we all know many don't place a lens on the cut out charts to verify that the lenses will cut out properly. I'll throw a plug in for http://www.thelensguru.com, the only place to get cut out charts. It's a great lens for the odd shapes where the optician might not know what segment height is appropriate. Keep in mind that this lens is a solution to a problem not a catch-all as mentioned above. I hope this sheds some light on a great company with some great technologically advanced designs.

I will add that the new fitting method by Varilux with the new comfort and the new physio is being touted to have a similar variable system, supply a segment height and the lab picks the short or standard design for you. I am sure they will allow you to specify the short or standard but it's being implemented as a solution. It is being touted as a variable design as well, which is interesting. From what I have heard the new comfort short is supposed to be a new design with the ellipse and the ellipse 360 not being phased out yet and I say yet because if they had planned to keep it around the lens would be the ellipse and the ellipse enhanced.

(don't rip my image I know that the reading circle and the inset arrows don't match exactly but for illustration purposes it works and it only took me 5 minutes to do)