Lets get this straight: Wavefront spectacle lenses

[drk]

No, what I meant was that a 1.6 or 1.67 or polycarb's relatively weaker optics would render inoperable the advantages that wavefront correction provides. It seems like a good idea in CR39, glass, or the ever-popular Trivex. Maybe Trivex does have a future!

[AWTECH]

drk states:

I don't doubt the Physio's good results, again, just some of the high-tech claims.

Well drk, I think you have a point. I would like to attempt to help validate your claim as follows:

See the responses from Pete, (the Essilor, guy), and compare to Darryl's answers, (not an Essilor guy),
Darryl contains fact after fact and supports his position.
Pete on the other hand, (and this is not personal), I know you work for the company but I doubt that you were responsible for the marketing verbage, has very little in the way of supporting facts to explain the technology.

My conclusion is this Physio is probably a good lens design and was created using traditional ray tracing methods. Once completed testing proceeded and marketing materials were developed. What we have been trying to pin down without any direct conformation from Essilor is, "What do they claim the W.A.V.E Front Technology is?" and how does it work?

[Darryl Meister]

I don't doubt the Physio's good results, again, just some of the high-tech claims

Regardless of whether Physio does or does not live up to its marketing claims (and I'm fairly confident that it will be a decent design either way), I will say this about Essilor's marketing of Physio: It is a bit out of character for them, in my opinion. Their last few product launches have relied on relatively simple marketing propositions, but they are using a truly technical story with Physio. As a technical marketing guy, I'm glad to see this shift in their marketing, and I hope that our industry -- as a whole -- is eager to step up to the proverbial "plate" to learn about all of the new technologies that have been emerging recently.

[drk]

Maybe I'll answer my own question by assuming that the "wavefront" benefits purported by Essilor are power dependent and material dependent, but still exist to some degree in all instances.

[drk]

Well I, for one, think that IF they are "cashing in" on going "over the head" of the average dispenser, that it is a negative development.

[Darryl Meister]

Darryl contains fact after fact and supports his position. Pete on the other hand, (and this is not personal), I know you work for the company but I doubt that you were responsible for the marketing verbage, has very little in the way of supporting facts to explain the technology.

I don't know that I've said anything to refute Pete's claims or explanations, and that certainly wasn't my intention. I'm just trying to clarify a few discussion topics that pertain to the application of these technologies, in general terms. You guys know me well enough to know that I'd just as soon keep the product-specific talk out of it, but Essilor's new marketing does bring up a lot of interesting optical stuff to discuss, as I mentioned in my previous post.

[drk]

For freeform and wavefront to have "hit the scene" roughly at the same time will lead to a lot of confusion in the industry. I think the wavefront thing is mostly hollow, but I think that the freeform/individualized stuff, when we determine who will really benefit from it (not unlike a ultra-high index lens), will be a significant boon.

[Steve Machol]

FYI: I've merged this thread with the I've merged the 'Wavefront spectacle lenses: Patent describes how they work' thread that was in the Ophthalmic Optics forum and renamed this one.

[drk]

Thanks, Steve. I have the urge to merge, as well.

[AWTECH]

Darryl states:

I don't know that I've said anything to refute Pete's claims or explanations, and that certainly wasn't my intention. I'm just trying to clarify a few discussion topics that pertain to the application of these technologies, in general terms. You guys know me well enough to know that I'd just as soon keep the product-specific talk out of it, but Essilor's new marketing does bring up a lot of interesting optical stuff to discuss, as I mentioned in my previous post.

I certainly agree with you on this matter I prefer to not discuss product specific items in the way this has developed, but this is such an unusual approach Essilor is taking. Using the same name for two different lens designs, Physio and Physio 360. SIMILAR BUT DIFFERENT? (whatever that means)

I know Pete or anyone in his position would not want to tackle their own marketing department. So I would say my conclusion regarding Pete's answers are not so much related to what he said but rather what he did not say. I would think if these marketing buzz words could be explained he would have. Pete seems very knowledgable and I commend him for not trying to explain some of the Essilor marketing claims.

Thank you Darryl for your insight and facts regarding this matter.

[Darryl Meister]

Using the same name for two different lens designs, Physio and Physio 360. SIMILAR BUT DIFFERENT? (whatever that means)

I think it would be easier to simply think of them as the "standard" and "free-form optimized" versions of the product. Really, most free-form lenses nowadays are also available in a semi-finished, non-free-form version.

[drk]

With all deference to the late ML and CS King:

"I have a dream. I dream of a day where a dispenser feeds information about a patient's visual requirements, anatomical and prescription specification, frame specification and position of wear, eye vs. head turn and tilt proclivities, and material choice into a computer program that makes a unique progressive design for that person, which is fabricated remotely and sent to the dispenser. No more guess work, no more imprecision. Just computer software loaded with wisdom. I have a dream, today..."

[Cherry Optical]

Essilor knows what it is, but you cannot get this from a pair of lenses that are in a semifinished form or even by free form grinding. Everyone is playing off of this buzz word, but the realiaty is that these types of lens will do very little to help your patients see better with a pair of glasses. The facts are this is the latest buzz word in the industry so everyone is coming up with their version.

Let me leave you with a thought. What happened to Atorics?? They were the greatest thing in our industry a few years ago. What happened to them? Another way of getting more money for a very slight increase in vision for 1% of the patients.

Now it is free form and wavefront lenses. Do these guys think we are so dumb that we cannot smell a Rat?? I worked for Essilor and I know their ways to get customers. Most of their products are very good but some are smoke and mirrors.

I would be intersted to know if you have done any studies to prove that 'these types of lens will do very little to help your patients'? The only reason I ask is that this is completly contrary to what our clinic base is experiening with their free-form patients. We have a number of recorded cases of people nonadapt to standad PAL designs and then become comfortable with their free-form fit.

Adam

[QDO1]

Hi Pete. QDO actually suggested that a lens blank was evaluated with a Hartman-Shack wavefront sensor -- or perhaps some other interferometer -- and later optimized based on the results, which I suspect is not the case (it doesn't seem very practical). Your explanation implies that the optimization is done during the initial lens design process using optical ray tracing, probably in conjunction with merit function terms related to coma. Is this accurate?

opps, what have I started!

[rinselberg]

[With Varilux Physio/Physio 360] Essilor's [intent] is to reduce certain wavefront aberrations inherent in [any] progressive lens, while Ophthonix's [intent] is to correct the wavefront aberrations of the [patient's eyes] - so they're really two entirely different technologies.

... just for review.


Regarding Cherry Optical's post (second post, above; just before this one), I think that dentum1 was talking specifically about the issue of wavefront technology WRT spectacle lenses, more than he (she) was talking about free-form technology.

I would be pleased to know if anyone has looked into that Ophthonix wavefront related patent that I posted earlier via http://www.optiboard.com/forums/show...85&postcount=6 and if they have any comments that they would like to share about the text or images of that patent application. (I haven't been able to view the images on my out of date Mac.)

[QDO1]

Hi Pete. QDO actually suggested that a lens blank was evaluated with a Hartman-Shack wavefront sensor -- or perhaps some other interferometer -- and later optimized based on the results, which I suspect is not the case (it doesn't seem very practical).

I actually sugested essilor optimised an interim blank, as part of the design process, and once they finished tweaking, they produced the new moulds using freeform technology..

Thus, the molds that the semifinished blanks are made from (on the front surface) have the optimisation in. This is possibly quite practacle, as the optimisation would be done in the digital domain..

here is the suggested process:
Analyse your best design yet using wave front technology ... see how you can improve it ... make an adjustment ... FREEFORM generate a new blank... check the results again ... repeat untill the analyser throws up no error, or significantly little error

Of course then, when they surface the back side, the algorythm they use will know the "new" geometry of the front surface, and optimise the back side by performing virtual ray tracing in the digital domain

Here is the chalenge to the manufacturers:
in the old days we were comparing a static design to a static design, and we knew where we were. For example: a Sola Grad will always be a Sola Grad

Now when we dispense a progressive lens, which we will call for arguments sake "NEW BRAND FREEFORM LENS", the design can vary from order to order, despite being called the same name, in this case "NEW BRAND FREEFORM LENS", so getting comfy and knowlegable about the characteristics and quirks of a lens is quite difficult now. At the moment it is like dispensing in the dark, and the only guide we have is that the marketing department for "NEW BRAND FREEFORM LENS" says It is the bees knees

For you to get me to philosophically buy into this technology you have to let me do a few things at my end of the process. I say this because at the moment the manufacturers are basically saying: 'trust me, this "NEW BRAND FREEFORM LENS" has the best algorythm ever made', and then in the next breath they say 'and the lens characteristics are XYZ' which is utter rubbish, because the design varies from patient to patient, implying the lens characteristics do too. Some young Jane, with 2 weeks training, who does what her boss tells her to do might fall for this... but any dispenser with real experience will see straight through it

So what do I want to do / see at my end of the process? I would love a digital device where I can scan a frame in, and be shown, what each design will look like interms of iso cylinders and distortion patterns. What would be even better is if I could actually be trusted to specify lens characteristics for my patients, and overlay the different manufacturers concepts over each other, so we can actually compare apples with apples

The chalenge to dispensers
Learn how to measure very accuratally, and be prepared to measure lots of more unusual things, soon

Here is another issue
a hypothetical patient buys the "NEW BRAND FREEFORM LENS", which is optimised for the RX, position of weaR... hell the whole lot is optimised. He buys it from ACME OPTICAL in the US. When the patient moves to the UK, and wanders through my door, 2 years down the line, where do I start? What did he have before? there is a lot of information to do with these lenses. Can this information be encoded onto the lens in a uniform way? so we know whats going on. It is us dispensers at the coal face that have to sit infront of the patient and untangle everything. At the moment the info we get is: ADD, make, design and sometimes base curve. In the future we will need a lot more

[fjpod]

I think this is the misconception that has everyone confused. You are both right, there isn't a great deal you can do about the wavefront aberrations of the eye -- at least without first measuring them with an aberrometer. However, Essilor is referring to the aberrations produced by the optics of a progressive lens surface, not the eye.

Progressive lenses produce a coma-like aberration that is distinct from the coma produced by the actual eye (and single vision lenses, for that matter). Coma is a type of optical aberration resulting from a variation in refractive power that causes the focus of an image point to spread—or “smear”—in a single direction (not entirely unlike the tail of a comet), instead of producing a sharp point focus. The change in power across a progressive lens surface produces a type of coma, which can be significant in certain regions of the lens. Unfortunately, this “aberration” is a necessary consequence of producing a change in Add power without visible bifocal lines.



Since the pupil samples a finite region (e.g., 3 to 6 mm) of the progressively changing lens surface, the power at the top of the pupil differs from the power at the bottom, creating a coma-like focusing error. Coma is most troublesome in or around the progressive corridor, where power is generally changing the fastest. Coma can be reduced along the corridor by lengthening it; however, this would result in less near utility in smaller frames. Coma is least problematic in the distance zone, where the power is relatively stable. In the peripheral regions of the lens, the effects of unwanted astigmatism completely overwhelm coma.

Daryl,

Great post. Is there a compilation and comparison of the various distortions of different brands of progressive lenses?...sphere, cylinder, coma, spherical aberration, and the like.

[Darryl Meister]

Thus, the molds that the semifinished blanks are made from (on the front surface) have the optimisation in. This is possibly quite practacle, as the optimisation would be done in the digital domain... Analyse your best design yet using wave front technology ... see how you can improve it ... make an adjustment ... FREEFORM generate a new blank... check the results again... repeat untill the analyser throws up no error, or significantly little error

In your scenario, the optimization wouldn't be done in the "digital domain," since physical measurements of the lens must be made between each step. Also, measuring a spectacle lens using a Hartman-Shack wavefront sensor -- which would likely require many separate measurements across the lens -- would require a great deal of computer processing to convert the data and make corresponding adjustments to the surface curvatures of the lens blank.

Finally, I suspect that the magnitude of the normal random and systematic errors between the design and production stages would be comparable to the level of errors you are trying to minimize between each iteration. Coma is already relatively low in the central distance zone (at least it's limited primarily by the design of the power profile), and you'd probably be more concerned about tweaking the curvatures to achieve the desired spherical-ish Base curve during the iteration stage. In the peripheral regions of the distance zone the lower order Zernike terms (astigmatism and power error) would overwhelm any coma. And you couldn't simply generate a new free-form lens blank; you'd have to create new molds after each design iteration if you are really trying to optimize the semi-finished product (which is one of the reasons that progressives cost so much to make).

What I suspect Essilor is doing is adding terms to their ray tracing and optimization system, since coma (and other wavefront aberrations) can be calculated analytically if you have enough information about the surface. This would be a much easier approach, and would probably work just as well for the type of aberrations they're trying to minimize. They could simply add a "coma" term, for instance, to the merit functions used to optimize their lens designs. Or, they could circumvent higher order coma altogether, and simply minimize power gradients in certain regions of the lens (since intrinsic coma in a progressive lens is a consequence of the progressive variations in mean power), thereby indirectly reducing coma. Though a "sanity check" using a wavefront sensor wouldn't out of the question.

[Darryl Meister]

I should add that higher order aberrations like coma apply to a "finite" pupil size, so Essilor would have to make some assumptions regarding this pupil size if they are specifically optimizing for coma. Pete may be able to elaborate on some of these details though.

[QDO1]

perhaps an Essilor employee has attended the Oakley school of naming.. Expect to see Wave-matter Optimised X2Y2Z2 optics soon

On a more serious note. It would be great if the manufacturers rolled out the proper educative documents, and training, before the products hit the market This part of the industry is a science, we are responsible for what we dispense, Im not selling something as incidental as picture frames or paperweights, I'm dispensing a product that my patients will go driving 2 tonnes of car in, or lorries, or planes etc.. I have a responsibility to know what I am giving them

[Pete Hanlin]

Hi Pete. QDO actually suggested that a lens blank was evaluated with a Hartman-Shack wavefront sensor -- or perhaps some other interferometer -- and later optimized based on the results, which I suspect is not the case (it doesn't seem very practical). Your explanation implies that the optimization is done during the initial lens design process using optical ray tracing, probably in conjunction with merit function terms related to coma. Is this accurate?
That is mostly accurate. As I attempted to describe, the physical analysis of the design was conducted after the design had been mathematically modeled and physically rendered. Its role was simply to verify that the wavefront had indeed been controlled. The term ray tracing is perhaps somewhat inaccurate. As I understand it, ray tracing involves analysis of the lens by tracing three individual rays. From my understanding of the analysis conducted on this design, complete sections of the lens are analyzed simultaneously (a column/beam of light approximating the size of the pupil). Regarding the size of this beam (which I believe was questioned somewhere else in the thread), the beam analyzed is 5mm in diameter in distance, 4mm in diameter in intermediate, and 3mm in diameter at near.

See the responses from Pete, (the Essilor, guy), and compare to Darryl's answers, (not an Essilor guy), Darryl contains fact after fact and supports his position. Pete on the other hand, (and this is not personal), I know you work for the company but I doubt that you were responsible for the marketing verbage, has very little in the way of supporting facts to explain the technology.
Well of course its nothing personal- I can't see why anyone would take that sort of comment personally! :)
As a matter of fact, I did have some input into the marketing terms (although far less involvement than I had in the creation of the technical education pieces used to describe the technology and the design).

I've attached two images at the bottom of the post. The first image represents the wavefront analysis of a 5mm beam of light passing through a Varilux Physio lens (with no distance power). The image depicts beams located +8, -4, 0, and 6 degrees to either side of the fitting cross respectfully. A competitor's latest lens design is shown in the second image. Essilor does not typically do "comparison" marketing, and I attach these here only for illustration.

In short, it is unfortunate and unintended if anyone misconstrues what I believe to be a rather carefully thought out explanation of the product- from both a marketing and technical standpoint. To the degree that I was involved in those messages, accept my apology for any shortcomings in scientific/technical content. I'm sure you would have a much more interesting conversation with several ladies and gentlemen from St. Maur, France on the topic of aberration, design, etc.

The fact is, this product was created via a design process which was able to analyze the wavefront passing through each surface and manufacturing processes which are capable of translating a design to the lens which eliminates/reduces/moderates the affects of higher order aberration and unwanted astigmatism. The extensive wearer tests that have been conducted seem to bear out the design's superiority over anything (Essilor or otherwise) currently out there.

[drk]

Thank you, Pete, for posting.

Are the thumbnails from a Physio or a Physio 360?

[Pete Hanlin]

The thumbnail is from a Varilux Physio lens. Most of the wearer tests were conducted with the Varilux Physio lens. The Varilux Physio 360 preserves the integrity of the design for patients with more complex distance prescriptions. Therefore, in a lens with no distance power there would be minimal- if any- difference between the two.

[AWTECH]

Thanks Pete for this info:

The fact is, this product was created via a design process which was able to analyze the wavefront passing through each surface and manufacturing processes which are capable of translating a design to the lens which eliminates/reduces/moderates the affects of higher order aberration and unwanted astigmatism. The extensive wearer tests that have been conducted seem to bear out the design's superiority over anything (Essilor or otherwise) currently out there.

Another statement by Pete from another thread re: Definity vs. Physio

Controlling the wavefront to reduce or eliminate higher order aberrations thus requires extreme control of that progressive surface. As mentioned in the other thread, the rendering of the design from mathematical concept to physical lens is accurate to 1/10th of a micron.

My problem is with the logic not the science.
a-The 1/10 micron accuracy sounds great but in the case of Physio spherically surfaced and processed using traditional fining and polishing would render such accuracy meaningless.
b-The best accuracy I would think the lens could be produced to would be about + or - 1.0 microns and only using diamond tools and precision freefrom lens processing equipment.
c-The location of the lens in the frame offers limited stability. There is much greater frame movement that 1.0 microns much less 0.1 microns
d-The molding of the lens blanks or in the case of poly injection would have much greater error than 0.1 of a micron

Just because the computer can calculate the digits to 1/10 of a micron does not mean that anything we are talking about in eyewear lenses ever will be produced to such tolorances. The greatest difference I know that will exist in the Physio and the Pysio 360 is how they are processed. Using traditional laps fining and polishing will create greater errors than digital diamond x,y,z surfacing with very minimal polishing.

For example if you process the standard Physio with equipment designed to do freefrom but set to cut standard spherical cuts these lenses will have a greater accuracy than those that are produced and then processed with traditional fining and polishing.

It would be interesting to know the degree of accuracy in terms of lens material needed to be removed to make these wavefront design improvements. Matching computer design capabilities to machine manufacturing capabilities is the beginning of the logic part I am having trouble understanding.

[Pete Hanlin]

The 1/10 micron accuracy sounds great but in the case of Physio spherically surfaced and processed using traditional fining and polishing would render such accuracy meaningless.
If the progressive surface were being created with the accuracy of traditional fining and polishing, you'd be absolutely correct in your skepticism. The progressive surface is the source of most higher order aberrations when light passes through a PAL to the eye. Addressing these aberrations is therefore accomplished by optimizing the design on the progressive surface- which requires the accuracy that has been aforementioned. The progressive side of the lens is not being ground by the laboratory using the traditional fining and polishing to which you refer- that surface is molded with a mold that has been digitally surfaced.

Significant distance Rx, which is placed on the backside of the lens, can cause significant alteration of the wearer's experience of the progression- which is why Varilux Physio 360 is available with a backside surface design which has been matched to the front side (also with the accuracy mentioned above).

The location of the lens in the frame offers limited stability. There is much greater frame movement that 1.0 microns much less 0.1 microns .
Perhaps you are misunderstanding the application of wavefront control regarding Varilux Physio? The aberrations inherent within the eye are not being addressed (and no claim to that effect has been made). It is the aberrations caused by the progressive surface which are controlled. Since the visual system is affected by aberrations in any of its elements (and, when wearing ophthalmic lenses, the PAL is one of those elements), resolving the aberrations in the PAL raises the potential for clear vision.

There is a company which is attempting to address the aberrations within the eye with an ophthalmic lens. I believe the company's name is Ophthonix, and although I am not privy to any of their research, I did attend a lecture given at the MAFO Symposium (prior to SILMO last year), and it appears they are able to address certain aberrations of the eye with an ophthalmic lens.

Just because the computer can calculate the digits to 1/10 of a micron does not mean that anything we are talking about in eyewear lenses ever will be produced to such tolorances.
Precisely one of Essilor's points regarding Varilux Physio. That is exactly why the physical lenses were analyzed after production- to ensure that the theoretical/mathematical design had indeed been translated to the physical lens (imprecision in molding being the reason coma control, etc., was not possible in previous designs). Two of the patents relevent to Varilux Physio pertain to the manufacturing process. The accuracy of the Varilux Physio mold is within 0.1 micron of the theoretical surface. Likewise, when the anticiapated wavefront is compared against the wavefront actually produced by a physical lens, the result is virtually identical.

There are three types of deviation common when molding a surface: Shape Deviation- low frequency occuring across the entire blank; Waviness- with a frequency between 0.1mm-5.0mm; and Roughness- which is higher frequency yet. The process used to create the Varilux Physio molds greatly reduces the deviations between the physical lens and the theoretical design.