Digitally Surfaced PALs (Free Form) Clarified

[AWTECH]

Agreed. I wish more specifics were available, but that's business.

I know in our case we offer as much specifics as possible unless the questions get into our specific processes we developed. As an example we are glad to explain in detail to our customers why we and how we our software works, but we won't give you our source code.

Posting or putting to much detail in general product literature just gets lost. With all of our technology being in the same building that our customers get their lenses from we have better access to specific information than many larger companies.

There are advantages and disadvantages to both large and smaller companies. The customers of each have to decide which of those advantages they consider more beneficial to them.

[YrahG]

I know in our case we offer as much specifics as possible unless the questions get into our specific processes we developed. As an example we are glad to explain in detail to our customers why we and how we our software works, but we won't give you our source code.

Posting or putting to much detail in general product literature just gets lost. With all of our technology being in the same building that our customers get their lenses from we have better access to specific information than many larger companies.

There are advantages and disadvantages to both large and smaller companies. The customers of each have to decide which of those advantages they consider more beneficial to them.

Is your progressive a multi design, does it change based on add alone or prescription as well?
Is your progressive asymmetrical?
Does your lens incorporate horizontal symmetry?
Does your progressive design change based on provided panto, dihedral, and vertex measurements or are these measures used just to compensate the prescritpion?
Does your design have the capability for variable inset?

If I had these questions answered by every manufacturer I would be able to do my job to a greater degree of accuracy, more than what the technology currently offers in the form of accuracy. If you can provide a break down of PRP to DRP, minimum seg hght, and a cutout chart I would be set.

[AWTECH]

YrahG

Is your progressive a multi design, does it change based on add alone or prescription as well?
Is your progressive asymmetrical?
Does your lens incorporate horizontal symmetry?
Does your progressive design change based on provided panto, dihedral, and vertex measurements or are these measures used just to compensate the prescritpion?
Does your design have the capability for variable inset?

We design lenses and the terms that different opticians adapt to try to describe various freeform lenses seems to me, to make it more confusing. The variables the optician can provide are frame information, standard prescription information including vertex distance.

So first I will have to know what you think each term actually means and what you should be able to specify

[Darryl Meister]

So first I will have to know what you think each term actually means and what you should be able to specify

The terms actually refer to pretty specific lens design features:

Is your progressive a multi design, does it change based on add alone or prescription as well? - multi-design refers to a progressive lens design that changes based upon the addition power; Design by Rx refers to a lens design that changes based upon the addition power and the base curve (distance Rx). These design changes generally include a change in viewing zone size or softness and a change in corridor length. Examples include SOLA Percepta, SOLAOne, Essilor Ovation, Essilor Accolade, etcetera.

Is your progressive asymmetrical? - asymmetrical refers to the use of a lens design with a near zone inset achieved through optical design; symmetrical, on the other hand, refers to a lens design with a near zone inset ahcieved through a mechanical rotation of the design. Asymmetric lens designs generally have significantly higher magnitudes of astigmatism in the nasal region of each lens, but much better binocular alignment between the distance, intermediate, and near zones of the right and lenses compared to symmetrical lens designs.

Does your lens incorporate horizontal symmetry? - horizontal symmetry refers to a lens design that has been optimized binocularly by minimizing differences in power, prism, and magnification between corresponding points on the right and left lenses to improve binocular fusion. This essentially achieves the viewing zone alignment benefits of asymmetry without the excess astigmatism in the nasal region of the lens, which would otherwise disrupt binocular fusion.

Does your progressive design change based on provided panto, dihedral, and vertex measurements or are these measures used just to compensate the prescritpion? - This is a very important distinction. Some laboratories may "tweak" the prescription using software in order to compensate the prescription for lens tilt. This is only effective, however, for the optics over a very small region of the distance zone. Certain free-form lenses actually calculate the correct prescription compensation at many points over the lens design in order to improve the optics of the entire lens. This requires a point-by-point adjustment to the asphericity at each point over the lens surface though, which requires pretty sophisticated optical design software used in conjunction with a free-form delivery system.

Does your design have the capability for variable inset? - variable inset refers to an adjustment to the inset of the intermediate and near zones in order to compensate for the effects of prism induced by the distance zone and the additional convergence required for higher addition powers. With traditional lenses, this is often calculated for each base curve and addition power combination. With certain free-form lenses, it is possible to compute the proper inset for every prescription combination as well as for the position of wear, which can also influence convergence. Examples include Zeiss Individual, Hoyalux iD, etcetera.

[AWTECH]

What I was trying to point out is these terms are not specific known terms by all opticians. And too much information offers a great deal of misunderstanding of the capablilties of one lens over another. Many of these features are maybe included in the design by one company with no marketing splash, while another company talks about how great their variable or multi this or that is. As an example the term Digital Surfacing was introduced a few years ago and immediately there were molded lenses being marketed as Digital, the devil was in the details, as they were referring to digital molds, which most of their competitors also used, but did not promote. All of a sudden the word Digital became a misunderstood lens. Was it digitally surfaced or was it a molded lens produced in a digital mold??? This is just one example

[Darryl Meister]

What I was trying to point out is these terms are not specific known terms by all opticians.

I agree, but I wouldn't necessarily invite people to make up new terms to describe these features, or attempt to redefine existing terms, when there are already perfectly acceptable and commonly used terms in our lexicon of lens design terminology. This would simply add further to the confusion.

As an example the term Digital Surfacing was introduced a few years ago and immediately there were molded lenses being marketed as Digital,... Was it digitally surfaced or was it a molded lens produced in a digital mold???

I don't know that the term digital surfacing is misunderstood by eye care professionals, but I do agree that some manufacturers have not been enitrely clear when it comes to identifying exactly how digital surfacing is actually used in the manufacturing process of their lenses.

But what troubles me the most is the general assumption in the marketplace that "digital surfacing" is synonymous with optically "customized" lenses, which has been precipitated by some free-form lens suppliers. Not necessarily all lenses that are referred to as "digitally surfaced" offer significant visual benefits to the wearer over traditional, semi-finished progressive lenses.

[AWTECH]

Also what enters into the degree of difficulty with the explaination of digital or freeform lenses is the range of optican knowledge and skills. For example you can have a skilled optician owned one man show store that is extremely knowledgeable the lens company needs to sell to and in another state or anothe town or right across the street you can have an optician in an unlicensed state that 2 weeks ago had another job, where they said, "Would you like fries with that"

Think about the difficulty of how much detail one of these can absorb vs the other.

You can keep feeding more and more information for marketing, such as lenses design using ray tracing. One type of multiple ray tracing is better than another because of X.

On top of all of this we are being asked to make a lens where the Dr. is prescribing within a 1/4 of a diopter.

Just some of the basic dynamics to work around

[Fezz]

I don't know that the term digital surfacing is misunderstood by eye care professionals, but I do agree that some manufacturers have not been enitrely clear when it comes to identifying exactly how digital surfacing is actually used in the manufacturing process of their lenses.

But what troubles me the most is the general assumption in the marketplace that "digital surfacing" is synonymous with optically "customized" lenses, which has been precipitated by some free-form lens suppliers. Not necessarily all lenses that are referred to as "digitally surfaced" offer significant visual benefits to the wearer over traditional, semi-finished progressive lenses.

:cheers::cheers::cheers:

[RT]

Does your progressive design change based on provided panto, dihedral, and vertex measurements or are these measures used just to compensate the prescritpion?

If it did, what percentage of the ECP's do you think would actually supply panto, dihedral, and vertex measurements with each order?

[AWTECH]

If it did, what percentage of the ECP's do you think would actually supply panto, dihedral, and vertex measurements with each order?

We digitally surface only and we provide the ability to set panto, dihedral and vertex.

I did a quick calculation to see what the difference was in a nomal non-wrap frame:

Refracted prescription: -0.50, -0.25, 32

We assume a non-compensated lens has 6 degrees of frame angle and 4 degrees of panto as very few frames have 0 for either of these. This also assumes a 13.5 vertex distance

Now if the patient picks a frame with 8 degrees of frame angle the new compensated numbers would be: -0.50, -0.24, 32

Then they pick another frame with an 8 degree frame angle but it sits 1mm closer to their pupil so the vertex distance is 12.5mm now. This new compensated prescription would be: 0.50, 0.23, 32

You can see by this example what a small change a nomal dress wear lens makes in the required prescription due to these individualized measurements. What is the chance of all opticians getting the same reading for these values? If this patient went to 10 stores and saw 10 different opticians, what are the chances each will measure the frame angle, the panto angle and the vertex distance exactly alike? Likewise if the patient has 10 different eye exams on the same day and asked for the prescription to be accurate to within 0.01 diopters, how many doctors could even write this? Would any of the 10 be exactly the same?

My point is that after years of developing technically advanced lens making capabilities in both processes and design there is a practical aspect that must be considered.

Does the frame angle get measured by one optician on the counter off of the patient while another one has a way to measure the width of the frame in the as worn position. These two different ways to measure will almost surely result in two different fram angles for the same frame. (The more correct one would be the one in the as worn position).

[Fezz]

If it did, what percentage of the ECP's do you think would actually supply panto, dihedral, and vertex measurements with each order?

What percentage actually has the tools to take these measurements?

What are the tools to measure these values and how can the average ECP get a hold of such equipment?

Does such equipment exist?

[AWTECH]

What percentage actually has the tools to take these measurements?

What are the tools to measure these values and how can the average ECP get a hold of such equipment?

Does such equipment exist?

Great point, yes there are some tools for this then there is the education of how to use these without producing more errors in lenses than good information that will actually produce a product the patient can see better with.

As I showed in my example the amout of change is so minimal vs the opportunity to really supply bad data for the facility making the lens that in my opinion a simple system that uses the existing known prescription information and the know frame information will result in the production of better quality lenses, maybe not as good as as one made with data that only one out of 100 Opticians could take accurately, but still very good, (and with less tolerance than the refraction produced).

[Fezz]

Great point, yes there are some tools for this then there is the education of how to use these without producing more errors in lenses than good information that will actually produce a product the patient can see better with.

Examples?

[AWTECH]

Examples?

I will let others from the different companies that offer these tools respond. I know of some but probably not all and I would do their products justice trying to decribe and explain how they work as have not used these on a daily basis.

We have our own tools in house to measure the frame wrap angles for wrap around frames.

We do make a math calculation for certain prescriptions where vertex distance will make some difference but it is rarely a significant correction to the total power.

Darryl, can probably explain any tools Zeiss has to measure the angles and distance.

[Fezz]

I will let others from the different companies that offer these tools respond. I know of some but probably not all and I would do their products justice trying to decribe and explain how they work as have not used these on a daily basis.

Good post Awtech.

You do expose one of the major shortcomings of this whole discussion. We have these fantastical, magical, most accurate lenses EVER, yet....how in the hell are we as dispensers supposed to measure them and supply you, the manufacturer, with the most accurate measurements to assure that the final end user gets exactly what they paid for? Who supplies the tools to do it? What classes are there to aide us? Are there classes to aide us?

I have yet to see a lens, or lab rep, that has come into my practice with the tools, the know how, and the experience to show me what to do or how to do it. Sure, many have said how accurate the new fangled whatever lens is....but yet, they can not supply me with the tools or the proper fitting techniques to supply them the magic numbers that supposedly make these new lenses so great.

Slight sidetrack:
I was visited by a Carl Zeiss Vision rep today and her manager (?) today. The topic of discussion was about the *NEW* Reveal lens that Zeiss and VSP have. They are pushing this product. The new rep was doing her best to impress me with how easy it is to submit this lens through VSP. I asked how long it has been since she became our new rep?

A year and a half! I have never met her.

When I pressed her on the measurement issues, she said that they did have a tool and could set up a in-office seminar to instruct me in its use. I told her that I actually had the little square widget tool, and that I had it for a while, and that I didn't need the seminar.

Now, I live and practice outside of Philadelphia, Pennsylvania. Not exactly New York or LA, but not exactly Obscure Town, USA either.

I have not seen a Shamir rep in two, maybe three years. I can't tell you the last time that I saw an Essilor/Varilux rep. I know that those three companies have measuring tools to help us take these various measurements that are supposed to insure the greatest progressives known to man. Yet, not one of these companies has provided my ofice with any of them, let alone the training on their use and why to use them. I have tried to get them, with ZERO success!

I am fortunate to have enough grey matter left, and lucky enough to have a few friends who have gotten me some measuring devices to assist me in these endeavors. But, if I have this hard of a time getting this kind of stuff, what does the ECP in the middle of Nowheresville, USA get this stuff?

This is way long winded, but I think most will see my point. So, where does one start in getting the proper equipment, and the correct use of that equipment to allow folks like Awtech, Shamir, Zeiss, etc, fabricate these so called sophisticated lenses?

It really is rather frustrating.

[Darryl Meister]

You can see by this example what a small change a nomal dress wear lens makes in the required prescription due to these individualized measurements.

I agree that, if you are only applying basic prescription compensation to the lens without modifying the actual lens design for the position of wear, many patients should not expect a meaningful visual benefit.

For that matter, since any eye care professional can download a simple prescription compensation program from OptiBoard free of charge, there is really very little reason to pay more for a lens that offers only prescription compensation without any real improvements to the lens design.

The interaction of the position of wear with the optics of a progressive lens is far more complex than a simple change to the distance prescription at the center of the distance zone though. This is why it is important to understand exactly what your "digital" or free-form lens of choice actually offers to wearers beyond traditional lenses.

What are the tools to measure these values and how can the average ECP get a hold of such equipment?

Darryl, can probably explain any tools Zeiss has to measure the angles and distance.

Inexpensive tools to measure the position of wear are available from certain lens manufacturers. Carl Zeiss Vision makes one available to eye care professionals to use in conjunction with Zeiss Individual. You should contact your local CZV representative if you are interested in our line of dispensing tools for customized lenses.

Several companies now offer more sophisticated digital centration devices that take position of wear measurements. The i.Terminal from Carl Zeiss Vision is certainly one example that has already enjoyed a great deal of success in Europe, but there are several more available to eye care professionals as well. I don't want this thread to disintegrate into an infomercial, so I'll keep the product-specific discussions to a minimum.

Of course, there are many benefits that these devices offer in addition to the capability of measuring the position of wear. The better digital centration systems on the market will take extremely accurate and precise measurements with high repeatability (to Fezz's point). Some even offer premium lens treatment demonstrations, patient tutorials, "magic mirror" functionality, and so on.

The overall patient experience is also enhanced with these devices, since digital centration devices a convey the practice's dedication to the use of cutting-edge technology for patient care. Focus groups have demonstrated that eyewear consumers would feel far more confident in purchasing premium progressive lenses that were measured using state-of-the-art digital centration technology compared to lenses that were measured by taking a plastic PD ruler to Vis-a-Vis blobs. Regardless of our dispensing ability, patient satisfaction often boils down to buyer perceptions.

[Fezz]

Regardless of our dispensing ability, patient satisfaction often boils down to buyer perceptions.

That may be the most important statement in this entire thread!

Well said Darryl!


:cheers::cheers::cheers:

[YrahG]

I know in our case we offer as much specifics as possible unless the questions get into our specific processes we developed.

YrahG

We design lenses and the terms that different opticians adapt to try to describe various freeform lenses seems to me, to make it more confusing. The variables the optician can provide are frame information, standard prescription information including vertex distance.

So first I will have to know what you think each term actually means and what you should be able to specify

I don't expect to be able to specify anything, I was invited by your statement to ask for specifics other than your processes. I have no interest in advertising your progressive lens design if you choose not to discuss it's merits please keep the benefits of your lenses to yourself.

The terms actually refer to pretty specific lens design features:

Is your progressive a multi design, does it change based on add alone or prescription as well? - multi-design refers to a progressive lens design that changes based upon the addition power; Design by Rx refers to a lens design that changes based upon the addition power and the base curve (distance Rx). These design changes generally include a change in viewing zone size or softness and a change in corridor length. Examples include SOLA Percepta, SOLAOne, Essilor Ovation, Essilor Accolade, etcetera.

Is your progressive asymmetrical? - asymmetrical refers to the use of a lens design with a near zone inset achieved through optical design; symmetrical, on the other hand, refers to a lens design with a near zone inset ahcieved through a mechanical rotation of the design. Asymmetric lens designs generally have significantly higher magnitudes of astigmatism in the nasal region of each lens, but much better binocular alignment between the distance, intermediate, and near zones of the right and lenses compared to symmetrical lens designs.

Does your lens incorporate horizontal symmetry? - horizontal symmetry refers to a lens design that has been optimized binocularly by minimizing differences in power, prism, and magnification between corresponding points on the right and left lenses to improve binocular fusion. This essentially achieves the viewing zone alignment benefits of asymmetry without the excess astigmatism in the nasal region of the lens, which would otherwise disrupt binocular fusion.

Does your progressive design change based on provided panto, dihedral, and vertex measurements or are these measures used just to compensate the prescritpion? - This is a very important distinction. Some laboratories may "tweak" the prescription using software in order to compensate the prescription for lens tilt. This is only effective, however, for the optics over a very small region of the distance zone. Certain free-form lenses actually calculate the correct prescription compensation at many points over the lens design in order to improve the optics of the entire lens. This requires a point-by-point adjustment to the asphericity at each point over the lens surface though, which requires pretty sophisticated optical design software used in conjunction with a free-form delivery system.

Does your design have the capability for variable inset? - variable inset refers to an adjustment to the inset of the intermediate and near zones in order to compensate for the effects of prism induced by the distance zone and the additional convergence required for higher addition powers. With traditional lenses, this is often calculated for each base curve and addition power combination. With certain free-form lenses, it is possible to compute the proper inset for every prescription combination as well as for the position of wear, which can also influence convergence. Examples include Zeiss Individual, Hoyalux iD, etcetera.

Thank you those definitions are textbook, I don't think I would have come close to the level of thoroughness exhibited in that post.

[YrahG]

If it did, what percentage of the ECP's do you think would actually supply panto, dihedral, and vertex measurements with each order?

If I could take a stab at it less than 5%. None of the technology that goes into these advanced designs is meant to create an idiot proof lens, unfortunately.

[YrahG]

Zeiss:
They have a type of plumb bob tool, which has a weighted dial and is pressed against the patients frame in the as worn position with the dial pointing to the correct panto measure. It is made of blue anodized aluminum about 65mm x 65mm square.

The individuals centration chart has a guage on the back of the chart which allows the frames dihedral angle to be measured.

Varilux:
I receieved a tool from a friend from the UK, it is a sophisticated looking PD device, which incorporates vertex, seg hght, PD, panto, and dihedral measures to be taken. It is made of plastic 190mm x 80mm and comes with printed directions for it's use.

Shamir:
Rumor mill has it they have their own device, I have yet to see one although I have heard about it profusely.

Images attahed below, these are the tools that I use. As discussed above the as worn dihedral angle can be less when taken off the patient. I try my best to adjust frames so that they exhibit 3 point touch even in the case of wrap frames I am looking for very little to no preasure on the side of the face, this will reduce the disparity what little is left was shown above to be negligable in the scheme of things or impractial to measure at best.

[Fezz]

1.) Zeiss:
They have a type of plumb bob tool, which has a weighted dial and is pressed against the patients frame in the as worn position with the dial pointing to the correct panto measure. It is made of blue anodized aluminum about 65mm x 65mm square.

The individuals centration chart has a guage on the back of the chart which allows the frames dihedral angle to be measured.

2.) Varilux:
I receieved a tool from a friend from the UK, it is a sophisticated looking PD device, which incorporates vertex, seg hght, PD, panto, and dihedral measures to be taken. It is made of plastic 190mm x 80mm and comes with printed directions for it's use.

3.) Shamir:
Rumor mill has it they have their own device, I have yet to see one although I have heard about it profusely.

Images attahed below, these are the tools that I use. As discussed above the as worn dihedral angle can be less when taken off the patient. I try my best to adjust frames so that they exhibit 3 point touch even in the case of wrap frames I am looking for very little to no preasure on the side of the face, this will reduce the disparity what little is left was shown above to be negligable in the scheme of things or impractial to measure at best.

1.) DOH!! I got one also...but mine is plastic. I am jealous!

2.) Got it too! Lucky us!!

3.) I have heard such tales. I have yet to locate one though!

:cheers::cheers::cheers:

[YrahG]

1.) DOH!! I got one also...but mine is plastic. I am jealous!

2.) Got it too! Lucky us!!

3.) I have heard such tales. I have yet to locate one though!

:cheers::cheers::cheers:

I have a plastic Zeiss one as well, I had that first and recently had my rep drop off a metal one. I have been waiting to see the Shamir device.

[Laurie]

Hello All,

I am in Indiana right now for an optical thing, and so FREEZING!!! Forgot what it is like to be up North in winter time!

Fezzy, your ears are good...there is something on the way from Shamir. They developed a measuring device, the 'Panorameter', to supply measurements for tilt, wrap, vertex...

I understand it is used in other parts of the world, just has not arrived here yet (shipping/customs, something like that)...

Vision Care Product News showed a pic once, it is plastic, with attachments that swivel to get quality as-worn measurements. Also, a cool thing about it, is that you can dial in the patient's PD when you measure wrap...as the angle will change depending on the PD, it is more accurate than laying the frame down on a wrap-angle chart.

In the meantime, you can find/dust-off your Distometer for VD... : )

If measurements are not given, the lens design software will default to norms for Panto Tilt and Wrap.

I have one that I am playing around with to help create a tutorial, so when they arrive, ECP's will understand how to use it.

: )

Laurie

[YrahG]

Hello All,

I am in Indiana right now for an optical thing, and so FREEZING!!! Forgot what it is like to be up North in winter time!

Fezzy, your ears are good...there is something on the way from Shamir. They developed a measuring device, the 'Panorameter', to supply measurements for tilt, wrap, vertex...

I understand it is used in other parts of the world, just has not arrived here yet (shipping/customs, something like that)...

Vision Care Product News showed a pic once, it is plastic, with attachments that swivel to get quality as-worn measurements. Also, a cool thing about it, is that you can dial in the patient's PD when you measure wrap...as the angle will change depending on the PD, it is more accurate than laying the frame down on a wrap-angle chart.

In the meantime, you can find/dust-off your Distometer for VD... : )

If measurements are not given, the lens design software will default to norms for Panto Tilt and Wrap.

I have one that I am playing around with to help create a tutorial, so when they arrive, ECP's will understand how to use it.

: )

Laurie

Thank you for the name of the device Laurie, I found an image:

http://www.visionmonday.com/ViewCont...3/Default.aspx

It looks similar to the Physio F-360 measureing device except it looks like a two piece device. I look forward to using it.

[Fezz]

Thanks for the update Laurie!

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