Pete, thanks for your replies. They have been very informative.
I had a fellow optiboarder in the office today who demonstrated some free-form PAL's. It was very interesting and eye-opening.
Pete, thanks for your replies. They have been very informative.
I had a fellow optiboarder in the office today who demonstrated some free-form PAL's. It was very interesting and eye-opening.
Clinton Tower
The intellect to live free is in short supply
ALT248=°
That is in fact a lie the design is on the front surface molded.Originally Posted by Pete Hanlin
This set up is discussed in the Vision councils data communications standard from years back, this does not necessarily make the technology better in any way or say it is "designed on the fly". This way to communicate could be used to provide a round seg if one choses or an older generation design. I think for the most part this is way to obfiscate the facts your company is trying to avoid. Also as a side note to change the front surface desing by using the back surface optics is just fixing a mistake that should never have been molded.In fact, the calculations for these lenses are done remotely (the laboratory uses a high speed connection to download the tool path for each lens- the calculation cannot be done on a desk top computer). This set-up is not unique to Essilor (my understanding is Zeiss Individual requires a remote connection as well). There are no pre-set files for the back surface design- each lens surface is individually calculated.
Fair enough, Zeiss Individual so far I have had the Shamir rep tell me the Auto II is "designed on the fly" I have not confirmed that yet so don't know it as a fact.BTW, I notice you didn't answer my question (i.e., what lenses do you think are "designed on the fly").
I find this statement interesting as your right theoretically you could change the design based on what is surfaced on the back surface, yet none of the patents pertaining to the Physio 360 or the enhanced mention such technology. Matter of fact although it is theoretically possible it doesn't make it feasable. The reality of the situation is that to use two surfaces to accompish what you suggest means you are beating around the bush.For anyone else that has been following this thread... Just because a lens is digitally surfaced from a blank having a progressive front surface doesn't mean it can't be "designed on the fly." I think we all agree a single spherical blank can be used to make all sorts of different progressive designs (this is the premise behind the FBS format). The design elements you place on the back surface change the lens into any number of different designs.
Well, you can do the same thing with a blank having a progression on the front surface. Depending upon the design you place on the back, you can shorten the progression, change the zones, or change the entire progression. In fact, theoretically you could place a design on the back surface which changes the lens back into a single vision lens if you made the right calculations.
Physio Enhanced Patents:
7207675
7207674
7413303
6909498
7427134
7210780
7229173
7223164
Great article here is a point also discussed:One of the great myths of digital surfacing is that somehow having a spherical front surface is the best format for a progressive lens. This is untrue for a number of reasons. For example, in a traditional format (progression on the front), ADD power is created by increasing the base curve. A traditional progressive lens with +3.00 ADD will increase in curvature by approximately 3 diopters on the front surface. Conversely, a progression with +3.00 ADD placed on the back surface will have a back surface that decreases in curvature by approximately 3 diopters. Professor Mo Jalie has an interesting paper which discusses this subject towards the end at the following link: http://www.ukoptometry.co.uk/wp-cont...-07revised.pdf
Again, digital surfacing is a cool technology which opens great new possibilities in progressive design. The best selling digitally surfaced PALs in the world are made by Essilor (over two million pairs of DEFINITY lenses have already been sold in the US alone), so I have nothing against the technology. I'm just hoping in 2010 we can start looking at this technology realistically (I'm a little tired of reading articles devoted to "How to sell digitally surfaced lenses").
"As the eye rotates behind
the empty aperture, the extent of field
which can be seen through the aperture
represents the apparent field of view. The
apparent field is influenced by the position
and size of the lens aperture, the larger the
aperture and the closer the aperture lies to
the eye, the larger the apparent field will be."
The keyhole effect that many manufactureres of FF lens designs talk about has a connection here if we consider the width of the design as the aperature then by bringing it to the back the apparent filed of view is widened, this means that even your companies design could benefit from a back surface design if they could come to grips with the fact that they would have to admit to the back surface being beneficial.
"However, the
relatively small increase in field offered by
a back surface progressive hardly warrants
such claims as “----- achieves wider fields of
view by creating the progressive design on
the back surface of the lens, rather than the
front.”
I enjoy Professor Jalies work I own all of his books and read all the aticles, I thoroughly enjoyed this one thank you for pointing it out, agree with both him and you that bringing the design to the back doesn't provide a huge increase in field of view but he does mention that it does provide an increase as well as you did in previous posts I believe 6% is what you said. If you can admit that two surfaces can be used to accomplish what one surface can then you should also logically be able to admit that if the field of view can be widened by applying the progression to the back even your companies design which has the progression on the front and the prescription on the back could benefit an additional 6% if you were to switch the prescription to the front and progression to the back.
As an aside you may enjoy a previous post of mine on the differences between apparent field of view and real field of view:
http://www.optiboard.com/forums/show...56&postcount=2
Although it doesn't discuss width of a progressive it does discuss the corridor length for a myope compared to a hyperope.
I have said before I can fit teh crapiest design properly and get better reulst compared to an office than fits the best design crappy. Please try and discuss ONLY facts. Lets's not read between any lines when we discuss.Above all, we need to stay focused on how all these PALs are being FIT. Getting the fit wrong by 1mm or so is going to impact the performance of the design a heck of a lot more than whether the lens is digitally surfaced or not.
Last edited by YrahG; 01-28-2010 at 07:21 PM.
Yes!!:d
If you have integrity, nothing else matters. If you don't have integrity, nothing else matters
Laramy-K Optical
Also consider the ISO tolerance on SV and PAL surfaces (ISO 10322-1&2)
SV
plano to 2.00 = Surface Power Error +/- 0.09; Surface Astigmatism 0.04
2.00 to 10.00 = Surface Power Error +/- 0.06; Surface Astigmatism 0.04
10.00 to 15.00 = Surface Power Error +/- 0.09; Surface Astigmatism 0.04
PALs
plano to 10.00 = Surface Power Error +/- 0.09; Surface Astigmatism 0.09
10.00 to 15.00 = Surface Power Error +/- 0.12; Surface Astigmatism 0.12
It becomes evident that the SV surface is held to tighter tolerances therefore would provide a more accurate base to work from. That means in low astigmatic powers the axis can be supplied more accurately. I don't think that this alone is significant enough to be a benefit in and of itself but you add up all the small benefits and you start to see a gain in accuracy.
Assume the worst case scenario in both the SV and PAL lets say a power of 15.00 the difference is going to be +/-0.04 n power and 0.08 astigmatism combine that with the worst case scenario on a traditionally tooled lens 0.04D that's +/-0.08 power with a 0.08 astigmatism. We're getting near that line in the sand where the error becomes significant.
Standards have nothing to do with actual tolerances. A manufactures actual curves produced are controlled by their own manufacturing standards. ANSI is a minimum standard not an absolute manufacturing fact for all manufacturers.
I was referencing the ISO standards for front curvature, ANSI is a whole subject in and of itself. Given the potential accuracy of FF lenses it may be worth revisting tolerances and maybe even creating a seperate class of tolerances for FF lenses but that's going off tangent. My posts was just to illustarte that a SV blank has the potential to be more accurate. In every case discussed here we are talking about the potential to realize greater accuracy. Actually provideing that accuracy is another story.
I am not sure if I got my point across. ISO and ANSI are both minimum suggested standards. As an example if your tires on your car are recommended to be kept at a pressure between 28 and 32 pounds but in a fleet they are checked daily and maintained at 29 to 30 pounds by this fleet management policies, is just going to produce reduced tire wear. Another person is still within standards if they drive at 28 pounds.
The standards are a broader range that some companies may adopt.
Understood, however any company that I have dealt with that has tighter standards than industry norms has made a point of letting me know. Even in the molding method digital production of moulds has lead to greater accuracy so I would highly doubt that anyone is sitting on the razors edge of any standard.
The mention of ISO standards here was to illustrate the reason why I feel a SV blank could be considered a better option to start a FF design, let's not get off on a tangent.
I believe that the simplicity of the surface also lends to greater efforts put into the design rather than to counter the design like in the previously mentioned posts. This could mean more time spent on improving the design rather than getting it to come out right. Lot's of fun and interesting stuff with FF lenses. Simply put our knowledge of optics has not changed with this new technology, same $hit different day as they say. Sure FF offers the potential for greater design flexibility but the software vendor has to choose to use this flexibility for anyone to see the benefits. So far I have heard alot about the technology and little about the design goals, this was similar to moulded progressives.
Last edited by YrahG; 01-29-2010 at 09:36 AM.
That is in fact a lie the design is on the front surface molded.
Ah, so I'm glad to see our discussion is not over! :)
Yes, the front surfaces of all the Varilux 360 PALs are molded. So are the front surfaces of FBS PALs! The difference is the front surface of an FBS PAL is spherical, and the front surface of a 360 PAL has progression on the front.
Either way (whether you start with a spherical front surface or a progressive front surface), you can create any design you want using the back surface. I've tried to explain this repeatedly in this thread.
The reality of the situation is that to use two surfaces to accompish what you suggest means you are beating around the bush.
On this point you are entirely mistaken. I'm not trying to be rude, but you seem resolute in stating Essilor does not use the back surface to modify a progressive front surface. In fact, I can cite several specific examples where Essilor uses two surfaces to acheive the final progressive design (generally speaking, we call this DDV- Dual Digital Vision... the front surface has a progression which has been molded and the back surface is used to modify that design and in some cases change it altogether).
I'll try to give a few examples, but the main point is what I've repeatedly said- just because you have progression on the front of a lens doesn't mean you can't modify the design "on the fly" to any parameter of your choosing. Actually, this is mentioned in a Zeiss white paper on Zeiss Individual (Zeiss indicates they prefer a FBS format because it is difficult to align the two surfaces precisely... Essilor has spent considerable resources on equipment dedicated to aligning the sides).
DEFINITY- First, DEFINITY is- by definition- a progressive design which is created by molding part of the progressive effect on the front and part on the back. Furthermore, both DEFINITY and DEFINITY SHORT are made from the same exact molded blank (yet they are definitely different progressive designs). The design can be made shorter or longer by digitally surfacing design elements onto the back surface (changing progression length is one of the "customized" features touted by FBS designs, as I recall). Additionally, the inset of the progression is changed in DEFINITY by changing the back surface design (the inset on the front surface is locked- because it is molded- it is modified by the back surface).
Accolade Freedom- Also has a progression molded on the front- but the progression length changes based on fitting height (through digitally surfaced customization of the back surface) AND we change the distribution of zones based on frame shape (again through the back surface).
Varilux Ipseo IV- The previous generation of Varilux Ipseo (which is personalized to the Head/Eye Movement Ratio) was actually FBS. However, we found we could do MORE customization of the design by placing part of the progression on the front of the lens and digitally surfacing progression on the back as well. How does that work? Depending on the H/E Ratio, a person with a +2.00 ADD can have as much as +4.00 ADD on the front or as little as +0.75 ADD on the front. The back surface will have anywhere from +1.25 - -2.00 of ADD power/digression. Additionally, the progression length changes based on fitting height (which is all accomplished on the back surface), and the zones are redistributed based on the frame shape (by modifying the back surface). Coincidentally, the progressive blank used to create Varilux Ipseo can also be turned into any of the Varilux designs (with the right back surface).
Varilux 360- The patent which covers the 360 calculation (which was discussed at the launch of Varilux Physio in 2006) describes a unique calculation which is applied to the back surface of the lens and which is based upon the design characteristics of the front surface.
Fair enough, Zeiss Individual so far I have had the Shamir rep tell me the Auto II is "designed on the fly" I have not confirmed that yet so don't know it as a fact.
I've repeatedly indicated that Zeiss Individual is designed on the fly- so no problem there. Regarding Autograph, I encourage you to carefully read their description of "Direct Lens Technology" at their website (link: http://www.shamirlens.com/ecp/patented-technology.aspx).
I truly hope we can continue to keep the tone of the conversation friendly, as I've received several PMs from people who are following our posts and find them informative. I know its hard to change a position once it is stated, but I think the main point of contention is the belief that having a molded frontside progression means you cannot truly customize the lens. In reality you can, and Essilor has numerous products on the market which do just this.
Best regards,
Pete
Last edited by Pete Hanlin; 01-29-2010 at 04:52 PM.
Pete, if you can take any of these molded blanks and create any pal design via backside digital surfacing, why have so many branded options? Just to create more market share? It sounds like you really only have two "freeform" blanks: Definity and the others, since they could all become each other with surfacing tweaks.
Bryan Finley, Florida Board Certified Licensed Dispensing Optician
Pete,
I was checking cylinder power availability for the Comfort and the Comfort 360 in the Frames Lens Guide. I see that the Comfort list cyl. power up to 4.00. The Comfort 360 lists cyl. power up to 6.00. I forget what material (1.67?). I don't have the guide at home to double check.
What I am having a hard time grasping is:
If the blank being used is the same, how can the 360 offer an extra 2.00 in cylinder power?
Thanks!
:cheers::cheers::cheers::cheers:
What a great thread! I feel like I'm bathing in knowledge....it feels kinda squidgee.....I likey!:cheers::cheers::cheers:
Okay, no I'm getting a little concernedWhat a great thread! I feel like I'm bathing in knowledge....it feels kinda squidgee.....I likey!
Bryan Finley, Florida Board Certified Licensed Dispensing Optician
Comfort is a conventional product made with a progressive blank.
Comfort 360 is made in a Freeform generator, and use plano blank.
Software accept up to 6 cylinder.
Mike
Last edited by OCP; 01-29-2010 at 04:00 PM.
WHOA!! How do they do that? Like, they produce a lens from black matter or something, just plug in the Rx info and "SHAZAM!", there it is?
Bryan Finley, Florida Board Certified Licensed Dispensing Optician
WOW!
They really are "Invisible bifocals"!!!!
Pete, if you can take any of these molded blanks and create any pal design via backside digital surfacing, why have so many branded options? Just to create more market share?
Each PAL design has its own technologies and purposes, and yes- market niches to fill.
On the Varilux side, the portfolio has two platforms- Varliux Comfort (which provides natural vision) and Varilux Physio (which adds WAVE Technology). Of course, you need short versions of each design (plus versions that feature customization to Rx, frame shape, and/or the position of wear). Varilux Ipseo IV is an exclusive-offering product, and Varilux Sport is a specialty niche (the Sport format is FBS, btw).
DEFINITY has its own design technology and market position as well (simpler portfolio- regular and short), and Accolade and the rest of the Essilor PALs are designed for the retail market- or for private practitioners. Generally, although there are a lot of products, there are specific customers who want each of those products (or we wouldn't make them). In fact, discontinuing a product is difficult, because inevitably there are practitioners who "love" that particular product and don't want to see it go away.
It sounds like you really only have two "freeform" blanks: Definity and the others, since they could all become each other with surfacing tweaks.
Regarding the number of blanks used to create DS lenses at Essilor, off the top of my head there are at least six different progressive blanks (Varilux Physio, Varilux Comfort, Varilux Ellipse, DEFINITY, Accolade, DEFINITY, and the blank used to create Varilux Ipseo IV). We also use spherical blanks to create Essilor Ideal products.
Although numerous designs can be made from a single progressive blank, the objective is to do only what is necessary to customize the design on the back surface. After all, there's no point in "recreating the wheel." If a molded surface can be used to create certain design components, its actually good to go ahead and use the molded surface.
Molds are great for their reproducability/consistency, which is why they are used to create the components of a design which remain consistent from lens to lens (even the most customized of designs have SOME components which remain consistent- e.g., most progressives increase in plus power in the lower portion of the lens). Digital surfacing is great for customizing/modifying the design, but digital surfacing is inherently challenging from a consitency standpoint- so it makes sense to limit its use to design components that require customization.
Why is digital surfacing "challenging" from a consistency standpoint? Well, the advantage of digital surfacing (the ability to unlock points on a surface) is also the biggest challenge of digital surfacing, because the points also have a tendancy to move around on their own if the process isn't tightly controlled!
In a traditional process, the entire progressive design is molded onto the front of the lens. If the surfacing process gets out of control, the distance power may be off a bit, but the design itself is usually not compromised (since its molded on the front of the lens, and the lab is generating the back surface). When you place the entire design on the back of the lens via digital surfacing; however, if the process isn't under control the design is compromised (because its being created by the process, instead of by a mold).
Digital surfacing is challenging to control because a.) variables in the process have a greater impact on the final product quality, and b.) it's harder to measure the accuracy of the final product. Several manufacturers are trying to develop equipment which can be used in the lab to measure the conformity of digitally surfaced lenses, but today most labs run test lenses in the morning and then trust the process is under control for the rest of the shift/day. Most of the major lens manufacturers have invested tons of money to ensure process control of their digital surfacing processes (which is why you see manufacturers creating big central DS labs where they can oversee the process). That's not to say local independent laboratories can't produce great digitally surfaced products, but it certainly helps if a manufacturer can provide process support (I know Zeiss and Essilor have certification processes for labs which digitally surface their lenses, I do not know what level of support is offered by Seiko, Kodak, and Shamir).
All this to explain why Essilor has- to date- adopted the DDV model for digitally surfaced lenses (molded progression on the front with additional customizing design components on the back surface). With DDV, the "base design" is locked into the front (via the mold), and the customization is done with the back surface (via digital surfacing). That way, you absolutely ensure the conformity of the base design while also having the ability to customize the design as much as you like. In other words, we use molds for their consistency and combine them with digital surfacing which provides almost unlimited customization possibilities. The result- hopefully- is customized products with a high consistency of quality from lens to lens.
No no no. RED matter. GEEZE! I swear did NO one else watch the Star Trek movie?! It's all spelled out there in 7.1 channel glorious Blu-ray high def now for your review. I swear I have to do all the work around here. *turning on TV once again* "Honey - grab me another beer would ya?" hehehe:DWHOA!! How do they do that? Like, they produce a lens from black matter or something, just plug in the Rx info and "SHAZAM!", there it is?
Oops, my bad:o
Bryan Finley, Florida Board Certified Licensed Dispensing Optician
What a great thread! I feel like I'm bathing in knowledge....it feels kinda squidgee.....I likey!
Glad someone else is enjoying this thread! Optiboard is a great place to exchange information.
I was checking cylinder power availability for the Comfort and the Comfort 360 in the Frames Lens Guide. I see that the Comfort list cyl. power up to 4.00. The Comfort 360 lists cyl. power up to 6.00. I forget what material (1.67?). I don't have the guide at home to double check.
What I am having a hard time grasping is:
If the blank being used is the same, how can the 360 offer an extra 2.00 in cylinder power?
There's no red, black, or pink polka-dotted matter involved... just a boring story.
Our traditional surfacing charts (base curve charts) go up to 4.00 diopters- however, as long as the blank will support the curvature, your laboratory can place 6.00 or even 7.00 diopters of cylinder on the back surface if they wish. Actually, this brings back a funny memory. When I managed US Market Quality for Essilor (a few years back), we had a lab that simply refused to put over 4.00 of cylinder into a Varilux lens unless Essilor supplied them with an official document indicating it was okay to do so (guess we live in a litigious society
With DS products, its a little more involved. The nature of 360 Optimization means the biggest benefit will be noticed with patients who have cylinder, so I suppose we should have anticipated the requests that came in after launch ("If 360 is so great for astigmats, why can't we go above 4.00 diopters?!?").
Well, as previously mentioned, process control is the key to digital surfacing- so an Essilor DS lab can't just "try" to create a power outside the range. The laboratories in the Essilor laboratory network which offer DS processing have pretty strict parameters- including the Rx range.
So, it took a special project to get the range increased. Essilor has a group called "OTG" which tests/certifies laboratory processes, and they had to certify the DS process up to 6.00 diopters of cylinder (they run a bunch of lenses in different designs on different pieces of equipment to ensure design conformance and stuff). I forget when the range expansion was added (end of '08 or somewhere around then), but our DS laboratories can now go up to 6.00 diopters of power (which is naturally limited by total power- going back to the thickness of the blank and all). Naturally, marketing was quick to get the range extension onto the availability chart- even though the charts for the traditional products still read 4.00 diopters.
If your local laboratory won't provide high cylinder jobs, perhaps I can dig up the "special" base curve chart! :bbg:
Last edited by Pete Hanlin; 01-29-2010 at 11:33 PM.
I am glad you brought up the Zeis Individual white paper, I have said in the past if all manufacturers were to provide such great literature our profession would be in a eutopia. So far I have cited references to various data substantiating my thoughts. I have seen nothing to sugget the Physio Enhanced lens design is modified by the back surface unless we count delivering the intended design as modifying the design.
Here is a simple end all to this conversation. If the Physio Enhanced and the Phyio 360 for that matter is so customized for the pateint why is "position of wear" data not required?
Since you cited the Zeiss white paper here is a passage:
"Therefore the position of wear can have significant impact upon the optical performance of a progressive lens, particularly the quality of vision through the central viewing zones"
I have attached an image I hope fair use applys here, it is from the Zeiss white paper. Darryl and Zeiss do a great job in simplifying the process, the imge shows the intended design and what happens to that design once a prescription is introduced. The zeiss paper shows the difference being subtracted from what is surfaced. I like to explain it to opticians as an Rx compensated for vertex you supply the lab with a prescription that is different than the prescribed prescription because when it is worn at the modified vertex it has the same optical effect as the prescribed prescritpion at the phoropters length. Now although Darryl does a great jobsimplifying this process and the image makes it looks like childs play, we are not working with lines, squares, or rectangles; we are working with curves spheres, cylinders, aspheric, atoric, and deformed conicoids. The image shows a surface being subtracted but in reality after this initial subtractin is done the design would without a doubt in my mind go through further iterations to make sure the difference between the intended design and the delivered design are within tolerance. I have seen "zero" evidence. I will repeat that "ZERO" evidence that suggests this new version of the Physio changes the intended design like you mention.
Pete, please this is one time I would love to eat crow. Provide me with some resources that verify the design is customized to the "INDIVIDUAL" not the design. I like to fit my lenses to the patients needs, not change the patients needs to fit the designs I sell. I hope this is what seperates me from the pack.
This is very good information, worth bookmarking this thread for. I have mentioned in previous threads that the any FF that incorporates the design component in the surfacing at the lab means that a manufacturer and their quality control which ensures the lab is recieving a blank that meets specs is removed. This is a check that we have grown acustomed to and the reputation of certain manufacturers have been built on the this quality assurance.Digital surfacing is challenging to control because a.) variables in the process have a greater impact on the final product quality, and b.) it's harder to measure the accuracy of the final product. Several manufacturers are trying to develop equipment which can be used in the lab to measure the conformity of digitally surfaced lenses, but today most labs run test lenses in the morning and then trust the process is under control for the rest of the shift/day. Most of the major lens manufacturers have invested tons of money to ensure process control of their digital surfacing processes (which is why you see manufacturers creating big central DS labs where they can oversee the process). That's not to say local independent laboratories can't produce great digitally surfaced products, but it certainly helps if a manufacturer can provide process support (I know Zeiss and Essilor have certification processes for labs which digitally surface their lenses, I do not know what level of support is offered by Seiko, Kodak, and Shamir).
Simply put, Poor Quality Lab = No FF Business.
This shoudl be a hard and fast rule, thsi means that all those offices looking for the best deal need to consider this process doesn't play well with cut corners so you really really really get what you pay for.
It's hard not to respond with you egging me on, like the sentence right after the smiley face. :finger:
Touche, a spherical moulded surface is still moulded just like a PAL surface, however see my previous posts about ISO standards, tighter tolerances require a SV mould to be more accurate. I am one of those kooks that believes that tighter tolerances are needed, especially with FF lenses. I also am optimistic that this will be a part of the next ANSI.
Love this statement, since ECPs (ODs, OMDs, and some Opticians) have knowledge of Seidel or secondary optics why is it information about PALs is still in our one demensional primary theory world. I would love to see a range of lenses that come from a manufacturer that vary in the aberrations they place the most merit with. For instance a lens with reduced marginal astigmatism as a primary design goal, another design from said company with reduced distortion or orthoptic design, etc. It could help fitters gain a better grasp on fitting and their patients needs.
Here is a simple end all to this conversation. If the Physio Enhanced and the Phyio 360 for that matter is so customized for the pateint why is "position of wear" data not required?
First, I'll agree with you that Darryl does an excellent job describing Zeiss' technology.
Second, I'll also agree that better SFSV blanks would increase the accuracy of FBS designs. I'll have to side with AWTECH regarding your discussion on tolerances, however.
Finally, you are changing your objection with each post. Your first objection was that a blank with a progression on the front surface could not truly be "designed on the fly." I believe I've given several examples that demonstrate that, yes- it can. Now your objection is the nature of the customization.
Incidentally, the graphic you posted is actually a good illustration of how 360 works- the design is altered to remove the negative impact of the distance Rx. Of course, it is possible to take it a step further with "position of wear" customization- which is found in both Varilux Ipseo IV (available in the US) and Varilux Physio F-360 (a design available in Europe). Both of these designs can be ordered with POW parameters. In fact, Varilux Ipseo IV also personalizes the design to the wearer's visual habits, which is beyond anything that has been discussed here.
Position of wear is a legitimate way to customize a PAL, but for it to make a significant difference, the position of the lens has to deviate substantially from the norm (the norm being around 7 degrees of panto, 8 degrees of wrap, and 12-13mm vertex). Its pretty rare when you can't fit a frame pretty close to these parameters (significant deviation from a normal fit only occurred in about 15% of a dataset of 50k+ orders I surveyed last year). In another illustration from the Zeiss paper we've been citing, I think they show a lens with significant power (+3.00 or so with cyl) with quite a bit of wrap and tilt. I'm not criticizing the illustration- merely pointing out you have to show a rather extreme example to demonstrate significant customization. Also, the quality of the base design is going to be quite important as well- I can customize an Essilor Adaptar to POW, and it still isn't going to perform nearly as well as a Varilux Comfort.
To end the matter simply (as you put it), I know the wearer can see an improvement with the Rx customization in Varilux 360 Optimization products, because I can measure the improvement on actual subjects. The original point of this thread concerned whether these design features result in any actual improvement. The data indicates that- in the case of 360 Optimization at least- the answer is "yes."
My apologies if the smiley face offended you- it was meant in good humor (and I take your wagging finger in good humor as well).
I'll close my contributions to this thread with the following: Proper fitting increases the performance of a design more than any of the "extras" we've been discussing. Seriously, it sounds as if you take great care in your fitting- and that's probably driving performance more than anything else you can do. Of course, we all (manufacturers and practitioners alike) are trying to provide ever increasing levels of performance- and I think there's gains to be had in the approaches of Essilor, Zeiss, and other manufacturers.
Best regards,
Pete
Last edited by Pete Hanlin; 01-30-2010 at 02:56 AM.
Anyone proffesional and clever eye doctor and optician, knows that pupil size dosent matter when talking about glasses. Contact lenses is a different question.
I donīt know if the mention Physio Enhanced is a better lens than previous design, but if it is, itīs for sure not because of the pupil size, but many will get that feeling only because it works better (if it does so).
We are therefor buying the story behind the lens.
As I have said many times, the industry (the design teams) will keep up invention new stories to sell their new lens designs, and itīs sometimes not fair for the sale rep, because they have to defend these stories with the knowledge that the story is not true in real life. Actually the design teams very often succes to convince their sales rep these invented stories.
Bad for our general knowledge.
Pete you got a hard job and will always be in crossfire because of this.
I fell with you.
Mike
Pete you got a hard job and will always be in crossfire because of this.
Actually, I have a challenging job- which is what makes it fun, and frustrating at times. :)
Seriously, my grandfather (who grew up in the Great Depression- so he had a pronounced appreciation of steady employment) gave me a little sign that hung on his cubicle (he worked as a Warrant Officer in the Pentagon for a number of years) that says "Thank God for the Troubles in Your Job." The main message being, if it weren't for the challenges of your particular job, ANYONE could be found to do the job at half of what they're probably paying you- so be thankful for challenges, because they pretty much account for your salary. Let's just say that- over the 7 years I've been working for Essilor, I've had several opportunities to be thankful!
Anyone professional and clever eye doctor and optician, knows that pupil size dosen't matter when talking about glasses. Contact lenses is a different question.
If you had said "the higher order aberrations within the eye do not matter when talking about glasses" you would have been mostly correct- because while you can resolve some higher order aberrations within the eye with a contact lens, an eyeglass lens cannot be used to resolve higher order aberrations within the eye. I say mostly because Zeiss is currently taking the impact of higher order aberrations within the eye into account when filling a lower order Rx. Also, technically speaking, if you can tolerate them I would imagine the best form of ophthalmic correction possible is found in a rigid gas permeable lens (which resolves irregularities on the cornea with a tear lens).
Regarding pupil size, however... From an optics perspective- pupil size has greater impact on the performance of an eyeglass lens than on a contact lens. I am not an expert in contact lenses, but as I recall the size of the pupil plays a role in determining the proper geometry of the CL (i.e., larger pupils require contact lenses with a larger diameter- either diameter of zone or physical diameter.
There are several reasons why this is true, but the first lies in the vertex distance between the lens stop (pupil) and the lens in question. In a contact lens, the vertex is pretty small- a CL sits about 3mm in front of the pupil iris (as I recall the anterior chamber is about 3mm deep- correct me if I'm mistaken). An eyeglass lens sits about 15mm in front of the iris.
The relevance of all this is seen when we ray trace light "backwards" from the retina out the front of the eye. Since a lens focuses light on the retina, we will see the light diverging as it leaves the retina towards the lens stop. The light making it through the aperature is still diverging, and in 3mm it will meet the cornea where we can measure its diameter. In another 12mm or so our rays will meet the back of the eyeglass lens- where it will form a larger diameter.
As the diameter becomes larger, it becomes harder to control the optics. To illustrate, we all know that anyone (with otherwise healthy eyes) will have 20/20 vision looking through a pinhole- regardless of refraction (because only one ray of light travels through the pinhole, and it is unrefracted). As the hole is increased in size, a greater column of rays passes through the lens stop- and any aberrations in the system become more apparent. Therefore, if an eyeglass lens has aberrations, those aberrations will become more apparent (at a faster rate than with contact lenses due to the relative vertices) as the pupil size increases.
In the distance portion of the lens, Varilux Physio is designed to control (eliminate or greatly reduce) higher order aberrations across a diameter on the lens that corresponds to a 6mm pupil size. In Varilux Physio Enhanced, higher order aberrations are controlled for an 8mm pupil size. Assuming this control actually occurs, we would expect individuals wearing the two lenses to notice sharper vision in low light conditions (and in fact wearers do significantly prefer Varilux Physio Enhanced over Varilux Physio in dim lighting conditions (p=<0.01).
Last edited by Pete Hanlin; 01-30-2010 at 02:26 PM.
If you are changing the definition of design on the fly then your right it is me that is misinforming on this thread.
I have mentioned the Ipseo as a truly inovative leap in PAL technology and your right that is a whole nother discussion in and of itself. I'll just sum p the Ipseo as the only lens that incoproates a patieents visual habts into the lens design in the form of a ratio feed into the design software known as the "gain" which is a reference to the ratio of head to eye movement when viewing off axis objects. This means the DESIGN IS CUSTOMIZED to meet the patients needs.
I am truly in awe. Either I neew a definition to what design truly means or youd do. Since there always exists the possibility that it might be me that is misinformed. I will conced in this, your lens DESIGN does get cleaned up on the back surface to deliver what was intended but the intended design was chosen by Varilux and the patient needs to fit that DESIGN. I like the Zeiss Individual sicne it will allow me to put my patient first and actually fits the DESIGN to my patients parameters.
Pete,
I do not feel sorry for you at all, I am not trying to give you or your product a hard time just trying to cut the fat fromt he meat. Matter of fact I envy a position such as yours, you get access to unadulterated data. To me this access is the holy grail.
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