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

[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.

[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?

[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.

[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?

[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.

[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.

[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.

[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.

[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

[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.

[mirage2k2]

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

[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?

[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?

[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.

[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...

[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.

[Darryl Meister]

;)

[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.

[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?

[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.

[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.

[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.

[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.

[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.)