# Optical Forums > General Optics and Eyecare Discussion Forum >  Lets get this straight: Wavefront spectacle lenses

## QDO1

Correct me if i am wrong...

*Freeform* = the technology or machenery with ability to generate a lens surface in 3 dimensional space, using the data from a computer file, which specifies the surface shape in three dimensions. Hence - a free-form genarator is the machine that does the work

This technological name is open to missinterpretation and missconception, just like "aspheric" is - as the lens surface is only as good as the information passed to it in the computer file, where manufacturers would like us to think all things freeform are good - infact, a freeform genarator is capable of producing both the best and worse optics

*Individualised lenses* (eg. ILT, Zeiss individual etc) = a lens design that takes into account the physical atributes of the frame, and face dimensions, allong with the optical atributes of the lenses, and possibly the sight test environment, and possibly other (not generally measured) atributes from the patient. The software in the computers used take the data, and work out how to make an optimum lens for the data set. The genearated lens may be made with conventional or freeform surfacing technology, depending on the type of surfaces the algorythm generates

This technological name is open to missinterpretation, just like "aspheric" is - as there is no standard ammount of "individualisation" needed for a lens to be individual

*WAVE technology (essilor point of view):* Essilor design a fairly good design for a progressive mold, and the finished INTERIM product was then analysed using a device similar to a Shack-Hartmann wave-front sensor, and adjustments made to the final PRODUCTION semifinished blank (front surface) mold. In other words - the front surface of the semifinished lens was optimised using wave front technology), what happens to it beyond that in terms of surfacing the back side might upset that optimisation (presumably Essilor have worked out some tollerances on that one). Essilor might then use that semifinished blank in a freeform or regular surfacing environment. This technology has nothing to do with mapping the corneal abberations of the patient, or other similar technologies

In theory essilor could apply this to a single vision front surface, and generate a rear surface progressive

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## AWTECH

I would say I completely agree with you on the terms Freeform and Individualized lens.  The Essilor WAVE Front issue is possibly a marketing and trademark rather than an application of technology with visual benefit.  I can not understand how What their WAVE Front is.  It is spelled with periods after the four capitalized letters leading me to believe it is a trademark.

I have not seen a response from Pete regarding this issue of Trademark vs technology.  I am open to the WAVE Front concept but have not been able to have anyone explain how it is practical for the production of a  lens that is surfaced and polished using laps.  As I understand true Wavefront technology maps multiple beams of light across a smalll area with nanometer accuracy.  If this is what it does, how does this accuracy help a persons vision with a large unstable lens in a frame resting on the nose.

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## mirage2k2

Where do some of the newer atoric/bi-aspheric lenses fit in?  Nikon have a lense called the SeeMax and the marketing suggests that it is individualized (consideration for rx and frame shape, etc.) and boasts better peripheral vision.  However, unlike the marketing for other atoric lenses, the marketing for this lense does not say too much about better peripheral correction for astigmatism.

Also, if the lense has aspherics on both sides how are you expected to grind an rx on the back surface?  Are these lenses only available finished? :Confused:

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## rinselberg

> ... I am open to the WAVE Front concept but have not been able to have anyone explain how it is practical for the production of a  lens that is surfaced and polished using laps. As I understand true Wavefront technology maps multiple beams of light across a smalll area with nanometer accuracy. If this is what it does, how does this accuracy help a persons vision with a large unstable lens in a frame resting on the nose.


I think that we had this same (or similar) question come up not too long ago in a slightly different context. "drk" started a discussion about wavefront corrected spectacle lenses. I brought up Ophthonix - a new line of wavefront corrected spectacle lenses (and contact lenses). These lenses are SV and are prescribed and made with wavefront corrections that are measured from the patient's eyes, during the refraction. See http://www.optiboard.com/forums/showthread.php?t=13597 Towards the end there's a post from AEOC, who actually dispensed some of these spectacle lenses (See http://www.optiboard.com/forums/show...4&postcount=15 )

Recently Ophthonix restyled their website and added some new content. I just found this


> 11) What happens when a patient's gaze angle shifts when wearing the iZon Eyeglasses? iZon Glasses include exactly the wavefront information that is required for each and every patient. Furthermore, the design is optimized over the entirety of the lens. As a result, there is not [a] detrimental effect as the gaze angle shifts.


source: http://www.ophthonix.com/globals/faqs.asp

? Make of that statement what you will. The optical math or "optimization" that is implied by that statement would be well over my head, technically; but this is as close as I have come to finding any kind of statement on this question.

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## QDO1

> I think that we had this same (or similar) question come up not too long ago in a slightly different context. "drk" started a discussion about wavefront corrected spectacle lenses. I brought up Ophthonix - a new line of wavefront corrected spectacle lenses (and contact lenses). These lenses are SV and are prescribed and made with wavefront corrections that are measured from the patient's eyes, during the refraction. See http://www.optiboard.com/forums/showthread.php?t=13597 Towards the end there's a post from AEOC, who actually dispensed some of these spectacle lenses (See http://www.optiboard.com/forums/show...4&postcount=15 )
> 
> Recently Ophthonix restyled their website and added some new content. I just found thissource: http://www.ophthonix.com/globals/faqs.asp
> 
> ? Make of that statement what you will. The optical math or "optimization" that is implied by that statement would be well over my head, technically; but this is as close as I have come to finding any kind of statement on this question.


the technology you are talking about here is actually measuring the patients corneal shape and distortions, and correcting it by adjusting the spectacle lenses.  There is yet to be an answer as to what happens when the patient looks off axis - because a spectacle lens does not move with the eye.  They do a similar thing with contact lenses, which makes more sense.  Wave front technology is mainly used in laser eye surgery, where corneal abberations are removed, according to the results of the enhanced corneal topography scan - and that makes perfect sense

The technology is basically using a "posh" auto-refractor - measuring the prescription required at many points in a plane infront of the eye, and producing a lens to correct to the measurements... the thing is.. who ever agrees with the results from an auto refractor?

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## rinselberg

References to "wave" or "wavefront" technology WRT prescription spectacle lenses are being remarked on this forum with increasing regularity. Essilor is now using wavefront terminology in conjunction with the new Varilux Physio and Physio 360 PAL (progressive addition) spectacle lenses. Ophthonix has already had some success in marketing iZON [SV: single vision] Wavefront-Guided [spectacle] Lenses.

Some forum members have expressed their puzzlement about how wavefront corrected spectacle lenses could be made to work, given the variables of the patient's gaze angles, relative to the lens optical centers, and also the limited precision of eyeglass frames, which will shift away from their exact initial adjustment over the course of daily use.

If anyone wishes to go deeper into this topic, I present (below) U.S. Patent Number 6,942,339 granted to Ophthonix, Inc.

As a user of an out of date Mac, I am unable to view the images that accompany this patent, but I think that most forum members will be able to view the images as well as the text of the patent. Much of it is "over my head", technically, but I think that if the audience that I am addressing would scan the text of this patent, with an eye out for the phrases "gaze angle(s)", "supervision zone(s)" and "transition zone(s)", they may find an understanding of this technology that they have not previously been able to conceive. The text of this patent is not very long. It is one of eleven (11) such recent patents held by Ophthonix in conjunction with this technology.

*Hypertext links to further information*

US Patent 6,942,339 "Eyeglass manufacturing method using variable index layer"

Ophthonix Wavefront-Guided Vision Technology (overview)


Yours truly.

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## Darryl Meister

> Essilor is now using wavefront terminology in conjunction with the new Varilux Physio and Physio 360 PAL (progressive addition) spectacle lenses. Ophthonix has already had some success in marketing iZON [SV: single vision] Wavefront-Guided [spectacle] Lenses


Keep in mind that Essilor is claiming to reduce certain inherent wavefront aberrations in a progressive lens, while Ophthonix is correcting the wavefront aberrations of the actual eye, so they're really two entirely different technologies.

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## Susan

From what I understand true wavefront technology begins with refracting using the wavefront lasor as in laski rather than conventional foropter refracting than sending the dats to the computer to produce the lenses now only available in SV. Essilors Physio marketed as W.A.V.E. ( not wavefront technology ) same smoke and mirrirs we are used to getting from Varilux but still a good product.

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## fjpod

> ... the thing is.. who ever agrees with the results from an auto refractor?


Ain't it the truth? It's a good starting point, but an actual prescription has more to do with the patient's symptoms, if any, and the habitual Rx.

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## dentum1

Folks,

Wavefront correcting lenses are a buzz word in the industry. The latest buzz word as far as I can tell. A few years ago it was Atoric lenses which was the buzz word. What happened to them???? This process is very experimental on the human eye and has the greatest benifit in laser surgery. The reason is that it can help the doctor improve the vision of a patient getting the surgery if done correctly. Laser surgery is not an exact sience either so the effects are very marginal. The next closest thing is a contact lens because it is worn directly on the eye. 

Putting this in eyeglass lenses is a joke. There is no way to stabalize a pair of eyeglasses to help the patient acheive this super vision since the frame moves up and down the nose and can easily move off axis. It is hard enough to correct a paitent with a high cylinder, yet alone keeping the eyeware in place to correct for these high order fields.

As far as the supposed correction of this high order is concerned, at least Ophthonix understands how this works and the benifits to the patient. 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.

You have to be smart about your choices and not believe the latest buzz word. The reality is that this is just a way to get your money.

Chow for tonight,

dentum1

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## Pete Hanlin

The Essilor WAVE Front issue is possibly a marketing and trademark rather than an application of technology with visual benefit. I can not understand how/what their WAVE Front is.
I'd be happy to attempt an explanation of W.A.V.E. Technology (Wavefront Advanced Vision Enhancement)...

QDO1 is pretty close to the mark regarding the definition... 
First, a design was created based upon the designer's understanding of how the visual system utilizes a progressive lens (informed by the compilation of clinical studies and design testing through the years). 

The design was then optimized through calculations which evaluated entire sections of the lens (a beam of light with the approximate diameter of the pupil in various points of gaze) and mathematically controlled (in some combinations eliminated totally, in others greatly reduced) higher order aberrations such as coma and trefoil- which primarily occur in the distance zone. 

In the intermediate, astigmatism was controlled to orient the axes vertically (further discussed below*).

In the near zone, power was controlled to provide a power/sphere slope which is more controlled and stabilized vertically (since the eyes tend to access different portions of the near zone throughout the day).

Where freeform (or digital surfacing**, which is the combination of the freeform equipment and the calculations which provide the CNC toolpath) comes into the equation is in the mold creation process. Coming up with a theoretical mathematical surface which does all of the above is one thing- actually acheiving that surface on a physical lens requires molds which are created by a digital surfacing process. The accuracy of this process is 1/10th of a micron (basically, if you blew the lens up to be a mile in diameter, the greatest deviation from the mathematical design would be 3/4").

Once the physical blanks were created, instrumentation which works on the same general premise as Shack-Hartmann (specialized to the purposes of evaluating a progressive lens surface) was used to confirm that the physical surfaces conformed to the mathematical model- and that, indeed, higher orders had been controlled, axis aligned, and near power stabilized. 

As QDO1 insinuates, the back surface of the lens also has an impact on the wavefront passing through to the eye. In lenses with low amounts of distance Rx, the integrity of the wavefront is largely unaffected. As distance power (i.e., back surface curvature) increases, the wavefront is negatively affected- particularly in the presence of astigmatism which is oblique in axis. Therefore, there is another version of the product called Varilux Physio 360. This lens shares the same front surface as Varilux Physio- but the back surface is created using a digital surfacing process. The back surface is calculated to provide the distance Rx- but is optimized in a way that negates the negative effects of the back surface. The resulting surface is not only aspheric/atoric, but is irregularly and specifically shaped to be matched to each point of the front surface. 

The results of clinical studies around the world involving over 2,000 wearers (conducted in Singapore, Europe, and the US) confirmed the real benefits to the wearer (the comparison tests were conducted using the Varilux Physio design- Varilux Physio 360 was tested seperately). Every aspect of vision tested (distance vision, intermediate vision, near vision, dynamic vision, width of visual field, and visual comfort) was rated higher in Varilux Physio when compared to both other Varilux designs (Varilux Panamic & Varilux Comfort) and the latest designs of all other manufacturers which were tested.

*Why is vertical alignment of astigmatism axis important in the intermediate periphery? First, when the axis of astigmatism is random (as it is in every other design I've seen), binocularity is impeded in the periphery. When the eyes leave the center of the design, one eye is looking temporally and the other nasally. If the axis of the astigmatism seen by each eye differs, binocular vision is challenged. Second, the eye tends to focus on the vertical element of any image, so orienting the axis of astigmatism vertically least disturbs the ability to focus. Sit behind a phoropter and give yourself 1.00D of unwanted astigmatism (i.e., add 1.00D above whatever astigmatism you may have). You'll find the orientation that is least disturbing is vertical (if your Rx has astigmatism, try this with with contacts on or something that resolves your natural astigmatism).

**Freeform processes represent a revolution in the way ophthalmic surfaces are created- however, it is important to note (as QDO1 did) that this is only the process and by itself does not create a better design. Its not unlike purchasing a TV capable of rendering a HD picture- without the actual HD programming, the TV produces a picture that is equivalent (or perhaps slightly superior) to a non-HDTV. Digital Surfacing represents the process of freeform and the programming produced by W.A.V.E. Technology (which the above paragraphs hopefully demonstrate is not simply a marketing term).

In the end, try Varilux Physio or Varilux Physio 360 (if you have above 1.50D cylinder) and measure the difference for yourself.

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## mirage2k2

since you work for essilor, what can you tell us about the designs used in the SeeMax, and any available essilor atorics/individualized.

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## Darryl Meister

> The design was then optimized through calculations which evaluated entire sections of the lens (a beam of light with the approximate diameter of the pupil in various points of gaze) and mathematically controlled (in some combinations eliminated totally, in others greatly reduced) higher order aberrations such as coma and trefoil- which primarily occur in the distance zone.


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?

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## AWTECH

Dentum1 talks about W.A.V.E. Front Technology from Essilor:

Consider the following....



> Wavefront correcting lenses are a buzz word in the industry. The latest buzz word as far as I can tell.





> There is no way to stabalize a pair of eyeglasses to help the patient acheive this super vision since the frame moves up and down the nose and can easily move off axis. It is hard enough to correct a paitent with a high cylinder, yet alone keeping the eyeware in place to correct for these high order fields.


To fit such a lens you will need a special frame made of 4 pcs of 20mm x 10mm titanium bar stock with a 40mm x 120mm x 4mm sheet of titanium for the frame face.  Each of the 4 titanium bars would have two mounting holes approximately 6mm in dia.  Then the patients skull would need to have 8 4.5mm drilled holes.  The surgical quality 8 stainless steel skull screws would then be used to attach this permanent frame to the patient.  Now you have a pair of lenses that will not move and your patient can take advantage of the 0.1micron Wavefront designed lens.

I am still working on styling however.  Any Beta testers for this process?

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## Darryl Meister

> Dentum1 talks about W.A.V.E. Front Technology from Essilor


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.

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## rolandclaur

Darryl, you need to write a book about everything you know about optics.  It will probably have to be divided in volumes and publications, several hundred pages long each of course.  I will be the first to vote for that and the first to purchase thank you very much...

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## drk

Neat idea about orienting the axes of unwanted astigmatism to a minimally vision distorting situation. You describe, I believe, ATR astigmatic error. Why not WTR, since it creates a "more manageble blur" than ATR?

Also, which higher order aberrations were corrected for, and are you able to share "root mean square" values of the degree of the pertinent aberrations, for a hypothetical power? 

I know that's a toughie, but I'm trying to discern the actual degree of improvement that is possible in aberration control, as well as the fundamental question: "What type and how bad are these aberrations in the first place?"

Please speak to the material's abbe value and how it will reinforce or mitigate the whole endeavor of lens aberration control.

And, I want a pony.

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## Darryl Meister

;)

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## AWTECH

> Please speak to the material's abbe value and how it will reinforce or mitigate the whole endeavor of lens abberation control.


 DRK states the above and I would like to ask Darryl to address this abbe value issue.

In addition to the abbe value of the material are these abberations exacgerated by the hard coatings used in the US?  If you put a 3 to 4 micron hard coating on each surface of a 1.67 index lens and this hard coating has an index of refraction of 1.50, how will this effect the potential for abberations?  

How are various Rx lenses affected by this different indexes, and what if one lens has a 4 micron hard coat and another has a 3 micron hard coat?

I have very limited ability to test this in our facility, and we have not dedicated the time to do so.

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## drk

AWTECH, I just posted the same question on another thread.  I wish we could pull this into one thread, maybe a new category: "Freeform/Wavefront"?  Steverino?

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## AWTECH

Thanks Darryl for the great explaination.  I could not find the words to make the point, and Essilor does not do a very good job of pointing out the difference in corrections needed for the lens surface.  They imply as many optiboard responses have indicated that their W.A.V.E. Front Technology is making adjustments for the eye.  It could be taken to mean that this technology from Essilor will somehow map the actual eye and make a perfect lens for it.  Which I know is not the case, but I can see optical dispensers misinterpeting the information and telling the patient such a story.

The Essilor information about there technology is as misleading, (although not inaccurate), to me as a credit card offer from a bank. 

Remember the pharse "Truth in Lending" well before long you will need to have been retired from the optical industry for years to remember "Truth in Dispensing".  Sad but apparently becoming true.

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## Darryl Meister

> Neat idea about orienting the axes of unwanted astigmatism to a minimally vision distorting situation. You describe, I believe, ATR astigmatic error. Why not WTR, since it creates a "more manageble blur" than ATR?


Unfortunately, it's not quite so easy. While the precise orientation of astigmatism in a progressive lens may vary, it can only do so within certain limits. For instance, you can't have completely horizontal or completely vertical astigmatism over the entire lens and still provide a stable viewing zone. Astigmatism at an oblique orientation is needed to blend the two separate curvatures of the distance and near zones together. Moreover, the astigmatism on the temporal side is near Axis 045, while astigmatism on the nasal side is near Axis 135. (The astigmatism distribution will be a symmetrical reflection around the umbilic -- or progressive corridor -- for simple designs.)

So, you can't really "choose" how you want to orient your astigmatism, but you do have _some_ degee of freedom without compromising the design or producing unnecessarily high levels of unwanted cylinder.

Also, while _legibility_ is an issue for uncorrected astigmatism (e.g., _vertical_ blur is more detrimental to reading text), it is less of an issue for the peripheral astigmatism in a progressive, simply because the blur is often too excessive to see much of anything clearly. The bigger issues are binocular power errors (as Pete noted) and an effect known as _skew distortion_.

Skew distortion is the apparent "shearing" -- or oblique stretching -- of images as a result of magnification from cylinder power at an oblique axis. It can be a somewhat disturbing perceptual phenomenon, especially when combined with motion. The higher the amount of cylinder at an oblique angle (often described as Astigmatism @ 45 in terms of the Zernike polynomials used for wavefront measurements), the higher the amount of skew distortion.

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## drk

Ditto's to dentum.  I belive what he says to be true.

Wavefront technology in Lasik has improved outcomes, to a degree.  As you can imagine, lasering something as soft as corneal tissue with it's hydration, etc, plus the irregular growth of tissue during healing HAS to reduce the effect, greatly.  Although the "registration" technique is rather gross, it is at least stable.

With contact lenses, the concept of aberration control can't feasibly extend past control of the contact's inheirent spherical aberration, but I doubt that has much "oomph" from my clinical experience.  Hype, once again.

With spectacle lenses, I would think the ridiculous amount of variables involved would make wavefront control virtually nil.

That's not to say that the Physio isn't superior due to other qualities, but I'm not buying the wavefront hype at all.

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## drk

Thank you, D.

Well, then, we are left with the whole notion of lens aberration control and any other lens design features that haven't been mentioned.

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

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## Darryl Meister

> DRK states the above and I would like to ask Darryl to address this abbe value issue.


If you're referring to wavefront aberrations, they are typically measured using a single wavelength as far as I know. (Though Essilor is most likely calculating the wavefront aberrations analytically using ray tracing, which you could theoretically due for any wavelength if you really wanted to bother with it.)

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## 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!

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## 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?

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## 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.

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## 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.

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## 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.

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## 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.

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## 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.

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## 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.

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## drk

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

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## 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.

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## 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.

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## 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..."

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## 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!

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## 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.)

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## 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.

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## 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

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## 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.

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## drk

Thank you, Pete, for posting.

Are the thumbnails from a Physio or a Physio 360?

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## 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.

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## 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.

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## Andrew Weiss

Thanks to all, and especially Darryl, Pete, Awtech and QDO1, for a great education.

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## mirage2k2

This thread is over my head but very interesting.  A few people have asked questions about the abbe value of the lens material used for these designs and either the questions have been unanswered or I've not understood them!

Are the newer designs attempting to correct abberations that are inherent in the lens material itself? - is this even possible?  If not, then what is the point of designing a great lense with superior (peripheral) optics and then to go ahead and make that lens in a material that has inherently poor (peripheral) optics?

Some (slightly off topic) examples are the Hoya Nulux EP (bi-aspheric) eyry 1.7 - abbe value = 36!  and the Nikon SeeMax - abbe value = 32!!!
Unless these designs overcome the poor abbe value of the lense they dont make much sense!  The Hoya Nulux EP is also available in eyas 1.6 - abbe value 42 - this makes sense - premium lense, thin, flat and still has a reasonable abbe value!

Can any of the experts make sense of all this?

ps: I'm not looking for free advice - I'm genuinely interested in this stuff!

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## Pete Hanlin

Are the newer designs attempting to correct abberations that are inherent in the lens material itself? - is this even possible? If not, then what is the point of designing a great lense with superior (peripheral) optics and then to go ahead and make that lens in a material that has inherently poor (peripheral) optics?
Abbe value is only one (relatively minor) component of a material's optical properties.  The abbe value of the eye's internal structures is only around 45 or so, which limits the impact of a material's abbe value on vision.  Also, a good deal of prism is required to create chromatic aberration sufficient to significantly impact vision.

I've attached a chart based upon the data collected by Meslin & Obrecht (sp?) regarding relative visual acuity and abbe value.  As noted on the chart, a wearer needs to look through approximately 6-8 diopters of prism to experience a significant drop in relative acuity.  So, in a -6.00 polycarbonate lens, you would need to deviate about 10mm from the optical center/axis of the lens before you _may_ notice the aberration.  For the -1.00 sph patient, chromatic aberration is almost completely negligible.  

As you correctly note, high index materials have low abbe values.  So, the dispenser who avoids polycarbonate in favor of 1.67 due to abbe concerns is perhaps a bit misguided.  

Perhaps of more importance, from a processing point of view, is the rigidity of the material.  Look through an Rx glass lens in a lensometer, and the crispness of the mires is amazing.  That's because the material is harder (and in some regards, easier to grind/polish to a precise curvature).  Crown Glass is largely unaffected by heat during processing.  Conversely, high index materials (and polycarbonate in particular) are sensitive to temperature deviations during grinding, fining, polishing.  I believe _this_ is the real issue with many "non-adapts" due to material.

Fortunately, the equipment and processes used by most labs are far more advanced today compared to the past.  Additionally, the new processes (discussed ad nauseum in this and other threads) is subject to far tighter controls- which can only improve the optical performance of ophthalmic materials.

Hope this is helpful,
Pete

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## mirage2k2

thanks for the response.  So abbe value only really comes into play in very high rx.  Now what if this -6 poly lense in your example had 4 diopters of base in or base out prism - am I right in saying that you wouldn't have to look far from the oc at all to see abberations/drop in visual acuity?

Also, on the point of the rigidity of the material, is it fair to say then that a softer material with a higher abbe (42), may not necessarily produce a better lense than a harder material with a lower abbe (33/36), since the softer lense is more susceptible to problems during processing?

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## Darryl Meister

> The term ray tracing is perhaps somewhat inaccurate. As I understand it, ray tracing involves analysis of the lens by tracing three individual rays.


The term _ray tracing_ really applies to just about any method of analytically calculating the optical performance of a lens system for an arbitrary principal ray. A _principal ray_ (or sometimes _chief ray_) is the ray passing from the object point through the either the entrance pupil or center of rotation of the eye after refraction through the lens. A typical ray tracing process often begins by calculating the refraction of the principal ray at each intersection with the lens surface and determining how the surface affects the vergence (or wavefront) of light at each of these intersections.

This can be done in more than one way. You can, for instance, ray trace a lens using a bundle of rays (e.g., 4 rays arranged in a square representing the pupil) centered on the intersection of the principal ray with each surface, calculating refraction by computing the angle of each ray with the normal to the surface. Or you can use the surface characteristics directly at each point of intersection of the principal ray, calculating the change in vergence at that point. You guys may use even a different method, still.




> The abbe value of the eye's internal structures is only around 45 or so, which limits the impact of a material's abbe value on vision.


Keep in mind that the eye is a fixed and somewhat centered optical system, so it is less susceptible to its own _lateral_ chromatic aberration. However, lateral _chromatic aberration_ -- which is a prismatic displacement that causes the infamous color fringing -- is the most bothersome effect produced by chromatic aberration in spectacle lenses.

That said, _monochromatic_ aberrations will certainly compound the blur and other negative visual effects produced by chromatic aberration. Consequently, a free-form process that improves optical performance will improve the overall performance of the lens and, consequently, wearer acceptance. If a wearer is going to purchase high-index anyway, which is usually the case for the prescriptions often used with free-form lenses, he or she will certainly get the best possible optical performance from the free-form version of the product if it has been fully optimized.




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


There aren't many that include comparisons of higher order aberrations like coma and trefoil, probably because most lens designers really haven't been too concerned about them in the past. Higher order aberrations due to large pupil sizes, like coma and spherical aberration, aren't an issue in single vision lenses until you get into extremely high powers.

In progressive lenses, they are a necessary evil in regions of changing (or progressive) power. Moreover, they are already relatively low in the stabilized viewing zones of the lens, unavoidable in the progressive corridor, and completely overwhelmed by astigmatism in the periphery. But that's not to say that Essilor hasn't reduced them in the distance zone of Physio even further compared to many other lens designs.

Nevertheless, not too long ago I ran across one paper that compares the wavefront aberrations of various progressive lenses. Look for _Comparison of aberrations in different types of progressive power lenses_, by Eloy A. Villegas and Pablo Artal, in a 2004 issue of Ophthalmic and Physiological Optics. It may be out on the Internet somewhere.




> 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.


My guess is that minimizing coma in a progressive lens probably doesn't demand all that much precision (at least no more precision than any other progressive), since you are really just minimizing the gradient, or rate of change, in surface curvature. It would probably be analogous to smoothing out medium spatial frequency differences in the free-form process.

----------


## William Stacy O.D.

> a good deal of prism is required to create chromatic aberration sufficient to significantly impact vision.
> 
> I've attached a chart based upon the data collected by Meslin & Obrecht (sp?) regarding relative visual acuity and abbe value. As noted on the chart, a wearer needs to look through approximately 6-8 diopters of prism to experience a significant drop in relative acuity. So, in a -6.00 polycarbonate lens, you would need to deviate about 10mm from the optical center/axis of the lens before you _may_ notice the aberration. 
> Pete


Sorry I didn't look at the chart, but the above begs to be challenged.  The human visual system does NOT need a "good deal of prism" to significantly impact vision.  Most people would notice the aberration in far less than 10 mm off center in a -6 polycarb lens if given the opportunity to compare it with the same off center vision in say a trivex, cr39 or any other kind of lens in the world.  Why do the manufacturers always downplay the effects of their distortions?  (I'm more invlolved in this same argument in IOLs than in SRx lenses, but the same logic applies!!!).

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## mirage2k2

and add about 4 base out prism in one lense and you can see color seperation right on the oc!

So if a patient has these kinds of problems in their lense, can these new designs do anything about it???  If not then the only option is a lense with a higher abbe!

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## Darryl Meister

> If not then the only option is a lense with a higher abbe!


There are a few other threads around that discuss chromatic aberration and Abbe values. You might have a look through a few, if you haven't already.

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## mirage2k2

yes but do these other threads discuss aberration with respect to the types of lenses being discussed in this thread?

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## Darryl Meister

> yes but do these other threads discuss aberration with respect to the types of lenses being discussed in this thread?


This thread is about wavefront corrections, and wavefront corrections do not reduce chromatic aberration.

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## mirage2k2

I'm sorry, its confusing because this thread used to be two seperate threads that have merged, one about Wavefront corrections and the other about freeform, Individualized and WAVE, etc.  Anyway, a few posts were questioning the value/effects of new hi-tech design when combined with low abbe lenses.

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## Darryl Meister

> I'm sorry, its confusing because this thread used to be two seperate threads that have merged, one about Wavefront corrections and the other about freeform, Individualized and WAVE, etc. Anyway, a few posts were questioning the value/effects of new hi-tech design when combined with low abbe lenses


WAVE refers to a "wavefront" correction. Neither free-form nor wavefront technology will reduce chromatic aberration.

----------


## mirage2k2

Thanks Darryl for all your help!  I've read the article you wrote on chromatic aberration (on opticampus) - it is excellent and very clear.  I'm just a novice so forgive me if my questions are out of context.  All I've really been trying to find out is if  there is ANY technology out there that can reduce chromatic aberration in a low abbe lens.  I think you've answered my questions - higher abbe less chromatic aberration.  Thanks again.

----------


## Darryl Meister

> All I've really been trying to find out is if there is ANY technology out there that can reduce chromatic aberration in a low abbe lens.


Unfortunately, for a given prescription or prism power, the only way to reduce chromatic aberration is by selecting a material with a higher Abbe value. (You can also minimize the prism power by selecting a smaller frame that fits close to the eyes.) However, minimizing the _total_ blur produced by the lens with technologies like free-form optimization should reduce _overall_ wearer discomfort in high-index materials by significantly reducing the effects of non-chromatic (i.e., _monochromatic_) aberrations.

Also, as I note in my article (and as Pete noted earlier in this thread), there are sometimes other factors that contribute to wearer discomfort in high-index materials, including processing aberrations, proper base curve selection, and material quality. Fortunately, these have all improved over the years. Further, the MR-7 and MR-10 materials used for 1.67 high-index are very robust.

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## mirage2k2

Excellent.  Thank you very much!

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## 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.


There's been a lot of (healthy) skepticism on this forum about the application of wavefront technology in spectacle lenses, especially WRT correcting the higher order aberrations that are unique to each patient's eyes - ala Ophthonix, for example. Far be it from a layman like me to speculate about how *well* such lenses would work, or for what particular visual conditions/diagnoses they might best be prescribed. But I would like to comment again on the *theory* of this invention - as much as I've been able to glean it from the overview provided by the vendor, via Ophthonix Wavefront-Guided Vision Technology, and from my own research, which has led me to US Patent 6,942,339 "Eyeglass manufacturing method using variable index layer".

This is the part of the patent text that made the most sense to me:


> The present invention utilizes the technology developed by the wavefront aberrator in which a layer of variable index material, such as curable epoxy, can be sandwiched between two plane or curved glass or plastic plates. This sandwich is then exposed to the curing radiation (i.e., UV light) that is modulated spatially or temporally in order to create spatially resolved variations of refractive indices. This will allow the manufacturing of a lens that is capable of introducing or compensating for low and high order aberrations.
> 
> In the simplest form, two lens blanks are sandwiched together with a layer of epoxy such that the lenses used in conjunction approximately correct the patient's refractive spherical and cylindrical correction to within 0.25 diopters. Subsequently, the epoxy aberrator would be exposed to curing radiation in a pre-programmed way in order to fine-tune the refractive properties of the spectacle lens to the exact spherical and cylindrical prescription of the patient's eye.
> 
> Another application of the present invention is to manufacture multi-focal or progressive addition lenses constructed with a layer of variable index material sandwiched in between the two lens blanks. The drawback of progressive addition lenses today is that, like regular spectacle lenses, a true customization for a patient's eye cannot be achieved due to the current manufacturing techniques. Using the two lenses and epoxy, a customized progressive addition lens or reading lens can be manufactured by appropriately programming the curing of the epoxy aberrator.
> 
> The present invention provides an opportunity to manufacture lenses that give patients "supervision." In order to achieve supervision, higher order aberrations of the patient's eye need to be corrected. Since these higher order aberrations, unlike the spherical and cylindrical refractive error, are highly asymmetrical, centering of the eye's optical axis with the zone of higher order correction ("supervision zone") is important. To minimize this effect, one could devise a spectacle lens that incorporates a supervision zone only along the central optical axis, allowing the patient to achieve supervision for one or more discrete gazing angles. The remainder of the lens would then be cured to correct only the lower order aberrations. An optional transition zone could be created between the supervision zone and the normal vision zone allowing for a gradual reduction of higher order aberrations. Again, all of this would be achieved by spatially resolved programming of the epoxy aberrator's curing.
> 
> In order to cover a larger field of view with supervision, a multitude of supervision "islands" might be created. The supervision islands then are connected by transition zones that are programmed to gradually change the higher order aberrations in order to create smooth transitions.



Credit: http://www.warpax.com/graphics_for_b..._graphics.html

Figure 1: Ophthonix spectacle lenses are pixelated. Each lens is an array of pixels or "microlenses", each of which has its own independently variable index of refraction, within a range that is centered on a nominal index (of 1.6). The index of refraction is set for each pixel as the lens is fabricated, using laser technology.



Credit: http://www.perret-optic.ch/optometri...ulux-ep_gb.htm

Figure 2: Gaze angles. The Ophthonix lens surface could be approximated as a two-dimensional grid, using discrete gaze angles, stepped across the full surface of the lens. At each gridpoint, a "supervision island" could be created, by programming the pixel at that gridpoint with an optimized refractive index, taking into account the sphere, cylinder and higher order (wavefront) corrections, as determined from the Z-View Aberrometer (autorefractor) data, for optimal vision at that exact gaze angle. The supervision islands could then be connected by transition zones, by _interpolating_ for the refractive index at each intermediate pixel (intermediate pixel: i.e., the off-grid pixels) to gradually change the higher order aberrations in order to create smooth transitions.



Credit: http://en.wikipedia.org/wiki/Linear_interpolation

Figure 3: Transition zones. There are supervision islands (see Figure 2; caption) at pixels (x0,y0) and (x1,y1); also (but not marked here) at (x0,y1) and (x1,y0) - four pixels which correspond to four of the gridpoints that were calculated (Figure 2) by stepping the gaze angle. A transition zone is created by interpolating for the index of refraction at each intermediate or off-grid pixel (x,y). I guess you could call it a "four-point interpolation." I'd go dust off my old math textbooks at this point (or do some more web research) - but I think that I've made my point. 


Why not have "supervision" at every single pixel, and do away with the transition zones altogether? Maybe it would take too much computing power - so many exacting calculations that it would be impractical to make the lens that way, even if it were theoretically possible. It might take too much time for the computer program to execute.


I'd be pleased if this post prompted some readers to look at the Ophthonix website material and then at this patent application. I haven't been able to view any of the images that would seem to be available with the patent text. I think that's because my Mac is so out of date - but I'm not sure. (Friend with Windows PC says she can't see the images, either.) If it seems that another layman posting on OptiBoard has just gone off the "tracks" again (relates to my rather obliquely selected _post title_ ...) - please articulate. I'm not trying to pull any wool over anyone's eyes. I just wanted to report on what I read, and what I thought I could make of it.


_There's another company working on the development of pixelated eyeglass lenses; see PixelOptics: Auto-focus spectacle lenses for presbyopes._

_What happens when optical science and software engineering collide? VirtualOptician. You may have seen the liftoff - but did you see the landing?_

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## Darryl Meister

> Why not have "supervision" at every single pixel, and do away with the transition zones altogether?


The term "pixel" is very misleading as it is used here. _Pixel_ generally refers to the smallest bit of light output or color from a monitor. However, Ophthonix is reducing the wavefront over a finite region of the lens roughly the size of the pupil diameter, which covers thousands and thousands of the cones or receptive fields in the retina (i.e., the "receiving pixels"). Further, each of these so-called "pixel" regions of supernormal in an Ophthonix lens is _asymmetric_, or vary in different meridians, since the higher-order wavefront aberrations of the eye generally are also asymmetric.

To make a long story short... Ophthonix is basically creating a honeycomb-like array of these supernormal viewing areas across the lens by varying the refractive index (sort of like a gradient-index lens). However, because of the asymmetrical shape of the power profile of each these supernormal viewing areas, these regions wouldn't normally be continuous with each other. That is to say, the edge of one region would have a different power profile than the edge of the adjoining region. (It gets a little more complicated than this, but this explanation should do for now.)

Because the power profiles of these viewing regions aren't continuous with each other, the variation in refractive index would have to change abruptly from one region to the next. This probably isn't physically possible with gradient index technology, and would most likely create a less pleasing visual transition from region to region, even if it were. This is where the _interpolation_ comes in, which essentially provides a smooth transition from region to region. Besides, it would require a lot more time and cost a lot more to make if you zapped _every single_ 3 or 4 mm zone across the lens with the laser.

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## emil_z

> Unless these designs overcome the poor abbe value of the lense they dont make much sense! The Hoya Nulux EP is also available in eyas 1.6 - abbe value 42 - this makes sense - premium lense, thin, flat and still has a reasonable abbe value!


My question as well. I have read through the entire thread, and still remain puzzled about why an apparently great new Physio design was not applied to high ABBE materials (or even reasonably good ABBE materials), but only to the worst of the lot: Poly and 1.67? I mean, would the resulting lens not be significantly better if made in CR-39 or Trivex, especially in hyperopic distance corrections?
Second, why go only for mid/high index materials when the majority of prescriptions are between +/- 3 diopters?

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## QDO1

> My question as well. I have read through the entire thread, and still remain puzzled about why an apparently great new Physio design was not applied to high ABBE materials (or even reasonably good ABBE materials), but only to the worst of the lot: Poly and 1.67? I mean, would the resulting lens not be significantly better if made in CR-39 or Trivex, especially in hyperopic distance corrections?
> Second, why go only for mid/high index materials when the majority of prescriptions are between +/- 3 diopters?


thats an interesting point, especially as the concept of free-form technology would come into its own in the higher RX's.  Whats ironical is that the lenses are generally only available on a limited range

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## AWTECH

> My question as well. I have read through the entire thread, and still remain puzzled about why an apparently great new Physio design was not applied to high ABBE materials (or even reasonably good ABBE materials), but only to the worst of the lot: Poly and 1.67? I mean, would the resulting lens not be significantly better if made in CR-39 or Trivex, especially in hyperopic distance corrections?


Can you shed some additional information for this thread regarding ABBE valve.

I know you referred previous posts to Opticampus which does contain a great deal about ABBE values.

My impression is that many opticans are shooting their guns at ABBE value, when I do not know if there is a way for the optician to know what the patients complaint actually is, other than the lens does feel comfortable.

If a patient says the lens does not feel comfortable, I have heard many opticians first thought is to look for the index. Once they spot poly they jump to ABBE value as the problem. Where this theory really got traction for me was the number of opticians whose next recommendation was to put the patient in 1.67, which has about the same ABBE value as poly.

I ask Darryl and others with specific knowledge on this to comment.

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## Darryl Meister

For starters, Physio _will_ be available in Hard Resin later this year. I imagine that Essilor started with 1.67 and Polycarbonate because these are their "premium" lens materials and Physio is their new "premium" lens design.

As for free-form lens materials, higher prescriptions will benefit the most from free-form optimization of progressive lenses. And, since higher prescriptions are generally ordered in a High-Index or Polycarbonate lens material, it stands to reason that a free-form lens design (which is also the _most_ "premium" option) should be available at the very least in higher index materials. Further, in low prescriptions, it really doesn't matter either way what the Abbe value is, so it wouldn't matter whether you're using High-Index or Hard Resin in the -3.00 to +3.00 D range. Consequently, there isn't much rationale behind offering low-index materials as free-form options.

Free-form is generally _not_ positioned (by dispensers or anyone else) as an improvement in optics over low-Abbe lens materials. Again, more often than not these wearers are going to get High-Index either way. And Free-form will improve their quality of vision in higher prescriptions, compared to conventional semi-finished High-Index lenses. Besides, as you noted, many dispensers switch their patients into 1.67 High-Index -- a low Abbe material -- with a great deal of success. (I addressed the possible reasons why earlier in this thread.)

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## mirage2k2

I am currently wearing lenses that have bad peripheral vision and the problem is largely down to the ABBE value of the material (chromatic aberration)!  I have high +rx with bags of prism and this rx in 1.74 material in not nice!

Here is the point, this thread covers all the latest technologies that are emerging and they all have the same goal which is to provide the best vision possible.  But for someone like me (and my optician) who is chasing around a problem that is material based, how do these technologies help at all!

There are lenses out there that could provide me, and lots like me, with great vision, i.e. atorics, however, most of these lenses are only available in high index - low ABBE material - so the design is somewhat flawed!  I could spend lots of $ on lenses like this just to find the vision is not much better since my key problem is a material problem!  High rxs dont always look good in high index material and some of the newer lenses on offer target higher rxs and yet are being produced in high index material!!!

The reference to Opticampus was regarding an article that Darryl wrote on chromatic aberration.  An interesting point in the article was the mentioning of special lenses (too expensive for opthalmic lenses) that reduce chromatic aberrations by using a combination of high index and low index materials.  I wonder if this is a technology that is becoming affordable?  This type of material would compliment all designs mentioned in this thread.

The most significant thing I have learned from this thread is that in addition to ABBE value, the rigidity of a material is a determining factor in the quality of lense produced.  As Pete has stated and Darryl has confirmed, a more rigid material will suffer less from the "stresses" of processing (grinding, polishing, etc.) and likely produce a better quality lense.  Perhaps this is partly why glass provides superior vision to plastic(?) and probably explains why my 1.8 glass lenses provide superior vision to my plastic 1.74.

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## Darryl Meister

> Here is the point, this thread covers all the latest technologies that are emerging and they all have the same goal which is to provide the best vision possible. But for someone like me (and my optician) who is chasing around a problem that is material based, how do these technologies help at all!


But these technologies were not meant to reduce chromatic aberration. And you could always choose a material that has a higher Abbe value...?

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## mirage2k2

a higher ABBE material is my only option, but its a shame that it is - and its annoying when you read marketing that suggests that this atoric lense or some other design lense is going to provide "the best peripheral vision".

On the topic of rigidity, is there much to choose between a 1.74 and a 1.67?  There is only a small difference in ABBE (33 vs 36) but do 1.67 tend to produce better lenses as a result of combined ABBE and rigidity?  And would agree that glass is better than plastic - from a purely optical point of view?  My optician back in the UK would ONLY make my lenses in glass because of my rx.  Now I'm in Australia and they dont want to touch glass!  They also tell me that nowadays there is not a lot of difference between the two.

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## Darryl Meister

> its annoying when you read marketing that suggests that this atoric lense or some other design lense is going to provide "the best peripheral vision".


But they do for a given lens material. Since you're a software engineer, I'll pose an analogy: Increasing the RAM in your Pentium II computer may improve its overall performance, but it's still not going to perform as well as a Pentium 4 computer with more RAM. And you wouldn't blame your RAM if your Pentium II computer wasn't as fast as a Pentium 4. ;)




> On the topic of rigidity, is there much to choose between a 1.74 and a 1.67? There is only a small difference in ABBE (33 vs 36) but do 1.67 tend to produce better lenses as a result of combined ABBE and rigidity?


Rigidity is certainly no guarantee of "better optics." It just reduces the likelihood of certain processing aberrations. And there are really several factors to consider in terms of processing, including heat deflection temperatures, hardness, and flexural strength.

Also, 1.74 High-Index actually has a slightly higher Abbe value than 1.67 High-Index (at 32). You would probably have to move into MR-8, Finalite, or some other 1.6 High-Index material with an Abbe value in the 40s to see a meaningful difference.

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## chip anderson

Where did any of us ever get the idea that "improvements in technology" were to "provide better vision?"  Most "improvements in technology" are to "Attract a higher market share or market value, period."  Even Der. Miester has told you that the purpose of aspheric technology is to "more nearly mimic corrective curve lenses."   Logicly this means that corrected curve lenses are better but they are older technology made of older materials.

Perhaps it is time to go back to "corrected curve lenses."   People saw very well out of lots of old designs, Ziess Puctal, B&L (trade name escapes me at the moment), Contintal had one,  Modern Optics had several.   

New = Most recent.     Best=Most applicable for the job.
New does not equal better, much less best.   Sometimes better means better than the piece of junk we had yesterday.

Chip

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## fjpod

> Perhaps it is time to go back to "corrected curve lenses." People saw very well out of lots of old designs, Ziess Puctal, B&L (trade name escapes me at the moment), Contintal had one, Modern Optics had several. 
> 
> New = Most recent. Best=Most applicable for the job.
> New does not equal better, much less best. Sometimes better means better than the piece of junk we had yesterday.
> 
> Chip


Was the B&L called Orthagon?

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## mirage2k2

Great analogy Darryl! :D 

I've looked at Finalite but my optician only deals with nikon and essilor - I looked at the SeeMax which could be great for me but the ABBE is 32! Although the overall vision might be better I'll still have the color seperation (which I see almost on the OC!) as a result of +5 base out prism. Incidentally, I'm seeing my optician in an hour to discuss the options:) 

Aren't some 1.67s 36 ABBE?

Anyway, since there is all this new technology happening, wouldn't it be good to research the use of mixed index material? Thanks to your help, I now understand that none of the new lens designs can reduce chromatic aberrations - the problem is in the material and not in the design! So, is there any research being done for a mixed index material? I'm guessing that for a plus lense the high index would be in the OC and then the index would reduce towards the periphery ... and then some fancy aspheric curve would deal with the vision in the periphery?

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## Darryl Meister

> Logicly this means that corrected curve lenses are better but they are older technology made of older materials.


_Optically_, you're exactly right: Aspherics aren't any better -- at least until you get into cataract lenses, which aren't especially common anymore. But, _cosmetically_, aspherics are thinner, flatter, and lighter in weight -- with less eye magnification.




> Was the B&L called Orthagon?


_Orthogon_. Very close.

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## Darryl Meister

By the way, for those who are interested in this sort of stuff (all four of you ;))...

AO's was the _Tillyer_
B&L's was the _Orthogon_
Zeiss's was the _Punktal_
Shuron's was the _Widesite_
Continentals's was the _Kurova_
Univis's was the _Best Form_
Titmus's was the _Normalsite_

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## mirage2k2

> Where did any of us ever get the idea that "improvements in technology" were to "provide better vision?" Most "improvements in technology" are to "Attract a higher market share or market value, period." Even Der. Miester has told you that the purpose of aspheric technology is to "more nearly mimic corrective curve lenses." Logicly this means that corrected curve lenses are better but they are older technology made of older materials.


But the aspherics look great!  :Cool:   These days it has almost become unacceptable to walk the streets with milk bottles for glasses!!!  :Nerd:   People want to look good as well as see good!  I looked at my wedding photos the other day - my glasses were almost as big as my face and my eyes looked huge!!!  I preferred the vision in my best form lenses but with my new aspherics I look normal again:D

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## rinselberg

> Aren't some 1.67s 36 ABBE?


Hoya 1.70 with Abbe 36 ...
http://www.hoyaopticallabs.com/170_eyry.htm

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## fjpod

> By the way, for those who are interested in this sort of stuff (all four of you ;))...
> 
> AO's was the _Tillyer_
> B&L's was the _Orthogon_
> Zeiss's was the _Punktal_
> Shuron's was the _Widesite_
> Continentals's was the _Kurova_
> Univis's was the _Best Form_
> Titmus's was the _Normalsite_


Good grief.  I remember having to memorize all these for the national boards back then.

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## mirage2k2

I've just figured out how to quote so I thought I'd quote myself :D 





> Anyway, since there is all this new technology happening, wouldn't it be good to research the use of mixed index material? Thanks to your help, I now understand that none of the new lens designs can reduce chromatic aberrations - the problem is in the material and not in the design! So, is there any research being done for a mixed index material? I'm guessing that for a plus lense the high index would be in the OC and then the index would reduce towards the periphery ... and then some fancy aspheric curve would deal with the vision in the periphery?


Any takers?

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## Darryl Meister

> Hoya 1.70 with Abbe 36 ...


Here is a pretty comprehensive list.




> is there any research being done for a mixed index material?


What you're referring to is known as a _gradient index_ lens (or GRIN), and it would be relatively expensive to utilize for a spectacle lens -- at least for the advantages it would provide.

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## mirage2k2

thanks, great link:cheers: .  Are gradient index lenses something you see as becoming affordable, i.e. do you see a use for them in specs in the future - all things get cheaper right?  They would certainly be useful in very high rx in high index, combined with free-form/double aspheric/premium lenses - where the customer is already spending big.

BTW saw my optician and he is warming to the idea of finalite or hoya 1.6 :) 
If he can get me hoya I will definitely try the Nulux EP double aspheric:bbg:

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## Darryl Meister

> They would certainly be useful in very high rx in high index, combined with free-form/double aspheric/premium lenses - where the customer is already spending big


I imagine at some point GRIN spectacle lenses will be commercially available. Ophthonix is already using a similar technology for their wavefront lenses. However, I doubt GRIN technology will be used to improve Abbe value or to reduce chromatic aberration. Most likely, it will be used to produce changes in power (progressive lenses, wavefront guided lenses, and so on).

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## AWTECH

Is the only way for a practicing optician to determine if the patient has a problem with the material due to ABBE, by verbal questioning the patient and asking if they see multiple colors when they look to the sides of the lens?

I do not know of any to confirm an ABBE value concern at retail.

Please advise if there is any equipment that can determine the chromatic abberations.

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## Darryl Meister

> Is the only way for a practicing optician to determine if the patient has a problem with the material due to ABBE, by verbal questioning the patient and asking if they see multiple colors when they look to the sides of the lens?


Usually, if the wearer's problem is related to the color-fringing produced by lateral chromatic aberration, it will be the first thing they complain about -- and the complaints will include seeing blue or amber along white edges and that sort of thing. Axial chromatic aberration will result in reduced clarity in the periphery, but in my opinion this is less likely to elicit a complaint from the wearer.

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## mirage2k2

> Usually, if the wearer's problem is related to the color-fringing produced by lateral chromatic aberration, it will be the first thing they complain about -- and the complaints will include seeing blue or amber along white edges and that sort of thing. Axial chromatic aberration will result in reduced clarity in the periphery, but in my opinion this is less likely to elicit a complaint from the wearer.


Since I have these problems it seems apt that I speak from experience - I see color seperation and blur (out of focus) - the blur is by far the worst thing since you see things go out of focus as you look through the periphery.  But I have always put the blur down to the color seperation - perhaps the blur is the result of axial chromatic aberration?

Darryl, wouldn't the color seperation (LCA) also generate a certain amount of blur and general lack of visual accuity, since, in the most extreme case you could be seeing three of everything  :Confused:

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## Darryl Meister

> Darryl, wouldn't the color seperation (LCA) also generate a certain amount of blur and general lack of visual accuity, since, in the most extreme case you could be seeing three of everything


Yes, as I noted, axial (LCA) chromatic aberration will result in reduced clarity in the periphery. However, it may be difficult to tell whether the reduced clarity is the result of axial chromatic aberration due to Abbe value, the result of monochromatic aberrations due to poor lens design, or the result of both. In this case, minimizing the monochromatic aberrations by using a good lens design will reduce the overall blur.

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## mirage2k2

I'm looking at your article again - 

Lateral Chromatic Aberration (LCA) - this is color seperation generated by induced prism - looking away from the oc = decentration = induced prism - so this is mainly an off-axis problem?  Adding prescribed prism would compound this problem?

Axial Chromatic Aberration (ACA) - this is where the different colors have different focal points and this is the lesser evil? - so if and when this is a problem is it a problem in the whole lense, i.e. oc as well as off-axis?

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## Darryl Meister

Yes, sorry, I should have used ACA (axial chromatic aberration is also called longitudinal chromatic aberration, which has the same abbreviation as lateral chromatic aberration). Both axial and lateral chromatic aberration result in "color separation," and you are correct in your assessment. Lateral chromatic aberration will be worse in the periphery because of prism, while axial chromatic aberration will affect the clarity of the lens everywhere -- though the effects of axial chromatic will be compounded by both the color fringing of lateral chromatic aberration and the blurring effects of monochromatic aberrations.

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## QDO1

I suppose wave-front technology is only as good as the algorythm used, and the measurements used for the data

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## Cherry Optical

> 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.


I'd much rather hear it from you Pete.   BTW:  I think I know who's competitive lens you have choosen there.  Good call!

The lens seems to be performing well.  I have about a dozen pairs in the lab for current Panamic wearing dispensing Opticians, so that will be my test.  We currently have done 80+ Physio/Physio 360s so far with little to no problems.  My market will determine what I sell.

Adam

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## hardbox_happy

Darryl Meister,

i had read the article that you post on opticampus,have some question is that any progressive design, once the Add increase,that mean the reading portion,or the distortion will be more?

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## Darryl Meister

> i had read the article that you post on opticampus,have some question is that any progressive design, once the Add increase,that mean the reading portion,or the distortion will be more?


The distortion always increases as the Add power increases.

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## Barry Santini

> Yes, as I noted, axial (LCA) chromatic aberration will result in reduced clarity in the periphery. However, it may be difficult to tell whether the reduced clarity is the result of axial chromatic aberration due to Abbe value, the result of monochromatic aberrations due to poor lens design, or the result of both. In this case, minimizing the monochromatic aberrations by using a good lens design will reduce the overall blur.


Darryl,

correct me if i'm wrong, but peripheral (off-axis) color is correctly called lateral chromatic aberration, not longitudinal, which is on axis... yes?

barry

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## Darryl Meister

A lens technically suffers from both lateral _and_ axial chromatic aberration in the periphery of the lens. Axial (longitudinal) chromatic aberration still results in the blurring of colors in the periphery as each color comes to a focus at a different distance from the image plane, while lateral (transverse) chromatic aberration results in different image sizes for each color -- producing the infamous "color fringing."

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## Barry Santini

I say again that lens technology now widely exceeds to accuracy and precision of traditional refraction.

"this or this" ..."or that"... is soooo last millenium....

I for one, look forward to a new paradigm in refraction...and none too soon.

That said, we're stuck for now with what's been doin'. Who knows the following:

dioptric value of 20 feet

Dioptric value of 10 feet

Average dioptric value for Night myopia for 25 year olds, and for 45 year olds

New ANSI power tolerances for progressives

Mix the above all up on the right day and in the right way, and...

you get patient disatisfaction. All of the above is easy to address..right now!

...without any free form complexity and expense.

What da ya say? For me its let get refraction *removed* from being considered (somehow) a medical procedure, and let us expand it and bring it into line with current lens technology


FWIW

Barry Santini, ABOM

answers: 0.16D; 0.33D; 1.25D & 0.37D; respectively; 0.14D (now *that's* alot of possible additive power error to compromise distance acuity)

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## Barry Santini

and lateral color fringing called also be described as as variation of the aberration *distortion*, with respect to wavelength, yes?
Barry

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## Darryl Meister

> and lateral color fringing called also be described as as variation of the aberration *distortion*, with respect to wavelength, yes?


They are related, since they are both due to prism, but a lens with very little distortion can still produce a significant level of lateral chromatic aberration.

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