Great answer Peter. :cheers:Originally Posted by Mr.Powers
I guess this three pairs of lenses was THE lenses that turned Zeiss succes rate from 100% to 99.20 %. ?
Thanks.
Mike
Great answer Peter. :cheers:
I guess this three pairs of lenses was THE lenses that turned Zeiss succes rate from 100% to 99.20 %. ?
Thanks.
Mike
Hello Again,
Hope everyone had a fun and safe New Year celebration!
Back to topic, do pow/as-worn measurements matter?
I agree that VD probably doesn't have a big impact with low Rx's. Lens/Frame curvature matters, as does tilt...how much? Our patients and clients will let us know soon enough. I believe it has enough impact to make the switch.
Darryl, thanks for your note, best wishes for you and your family as well. : ) I've sent your question to the techs for exact clarification...as it is the holiday season, I don't expect an answer right away. However, I did speak to a lab rep where they do tons of personalized back surface ff, and it is also their understanding, that, when pow/as-worn data is given, and when the frame is sent in for tracing, the software changes the algorythyms (sp?), and the design changes (i.e. the placement of the near zone along the convergence path, handling aberrations, ect). This is one of the reasons it is difficult to show rotlex topographies of this classification of lenses, as each is unique depending on frame/patient/rx parameters.
Fezzy, I hope I was not included in your list of 'all education is biased', as I try really really hard, during CE seminars, to stick to science, not marketing. And, in my classroom (Go HCC!), brands are NEVER mentioned...only technologies.
So....are we all flying around on kites, or is this new way of making PALs and SV, personalized, back-surface FF lenses the wave of the future? I'll place my bets on the latter.
: )
Laurie
Yes, I do find it odd, and a little discouraging, that certain Shamir distributors in this thread seem to focus more on bashing Carl Zeiss Vision than on discussing the merits of the optical principles involved. In fact, another thread has been started in this forum solely for that purpose.Back to topic, do pow/as-worn measurements matter?
Since Creation is a traditional semi-finished lens, I can essentially summarize the opinions of at least two Shamir customers in this thread as follows:I ordered Creation for the rest of the custemers that having being complaining, and theres was no problems whit any of them. KISS = Keep it Simple Stupid
Limited customization is better than full customization
No customization is better than any customization
If either of you would prefer to continue offering only traditional progressive lens designs to your patients, instead of the latest-generation lens designs, that is certainly your prerogative. I'm not sure why you feel the need to keep comparing your products specifically to Zeiss Individual, however.
I also do not doubt that some customers may feel that "keeping it simple" is more in line with their particular business strategy, which is why most major free-form lens suppliers, including Carl Zeiss Vision, make simplified free-form lens solutions available.
After 20 years in the business, I cannot say that I have ever seen an eyecare professional run into a 33% (14/43) non-adapt rate for any progressive lens. This is indicative of a much greater underlying problem than simple progressive lens acceptance.we sold 43 pairs of indeviduels all whit the helps off the RVT Zeiss lent us. 14 of them complaint
While I would encourage you to use products that have only been successful for you, I would certainly like to know the location of the Carl Zeiss Vision lab that you have been using, since you are obviously not using a lab here in the US. I can have someone in your region follow up with the lab to isolate the source of the problem. I look forward to your post.
After some of the rather anecdotal comments regarding the use of this technology by different manufacturers, I think clarification from a person responsible for the implementation of this technology within the actual company would be best. I have already seen several several comments that I know to be invalid, so I would encourage more "definitive" answers whenever possible.I've sent your question to the techs for exact clarification...However, I did speak to a lab rep where they do tons of personalized back surface ff, and it is also their understanding
This is correct; you would need to analyze the lens using optical ray tracing for the position of wear to assess optical performance in this case, which would rely on measuring the refractive action of both surfaces and reconstructing the lens mathematically.This is one of the reasons it is difficult to show rotlex topographies of this classification of lenses, as each is unique depending on frame/patient/rx parameters
Last edited by Darryl Meister; 01-03-2010 at 05:20 PM.
Darryl J. Meister, ABOM
First of all I´m not bashing Carl Zeiss or Individual at all. Please feel free to tell me where I do that. I certainly know that bashing other products only give me mail from the moderators to stop the bashing, and with my years of great interest for progressive lenses, this is actually the only and one forum in the world where we can discuss this stuff. I would prefer to be a member of this.
It´s obvious that there is people reading here, that do not find Individual as the best progressive lens out there (just as Auto II, Impression and all the rest). I guess this forum is for all stances and not only for the PRO Zeiss people? Please correct me if I´m wrong.
As I say ones again, Individual is not a bad lens, but to get back to my point, Vertex and panto is not FIXED values and are nearly impossible to measure correct, and therefore I did only said, that these two measures should be standardize or removed. I know, from a personal view, that some times Creation works better than Individual. I guess this is because of wrong measurements of the Individual, but if that is the case, it will only confirm that some measures are dangerous to measure when you cant do it well enough, and because the measurement are not fixed.
Please just accept this standpoint.
I know for sure, that other here are thinking the same.
They, and I do not have the problem. The manufacturer does.
Not saying Zeiss is the only one. I say the INDUSTRY has the problem.
Actually I know Peter from the thread above, but he are selling not only Shamir lenses. He are, as I know, selling both Zeiss, Hoya and Essilor as well, but his statement is actually very relevant in this thread.
Mike
[QUOTE=Darryl Meister;325683]bYes, I do find it odd, and a little discouraging, that certain Shamir distributors in this thread seem to focus more on bashing Carl Zeiss Vision than on discussing the merits of the optical principles involved. In fact, they seem to have started another thread in this forum solely for that purpose.
QUOTE]
Actually I must say, this is very untruthful.
This statement only confirm that this forum is reserved the PRO zeiss people.
In the name of education, I hope this is not true.
Mike
Here is a short list, to get started:First of all I´m not bashing Carl Zeiss or Individual at all. Please feel free to tell me where I do that.
Example
Example
Example
Example
Example
There is an underlying implication in just about every one of your posts in this thread that manufactuers who offer forms of customization that differ from Shamir's are somehow offering substandard products and generally attempting to mislead eye care professionals. Even the title of your thread is essentially an accusation to this effect.
To that end, you have mispresented several facts in this thread and, as of late, you have resorted to singling Zeiss Individual out with rather questionable comments regarding its performance.
I am afraid that you seem to "know" many things that simply aren't correct. Assuming that you are acting within our posting guidelines, we (the moderators) are not going to require you to stop "bashing" a product or otherwise expressing deleterious remarks directed at another company or product. In fact, a few of our longstanding members even seem to make a hobby out of bashing certain companies.I certainly know that bashing other products only give me mail from the moderators to stop the bashing
While we certainly do not condone such behavior, we attempt to encourage open, respectful communication as much as possible.
OptiBoard is open to members of all opinions and financial affiliations. Nevertheless, as one of the earliest OptiBoard members on this forum, I can assure you that the success of OptiBoard has never been due to members attempting to advance the products or services of any one individual company.this is actually the only and one forum in the world where we can discuss this stuff... I guess this forum is for all stances and not only for the PRO Zeiss people? Please correct me if I´m wrong.[/
As for your continued insinuations that OptiBoard caters to "pro ZEISS" people, which any longstanding member would know is silly, you have actually mentioned ZEISS products more often in your posts than any "ZEISS" person. Usually in the context of how they compare to your own products. I, personally, keep asking you to stick to the principles, not the products.
Further, I would encourage any member who would like to endorse their products and services outside the context of relevant discussion to sponsor a banner ad on this site, which has the added advantage of providing financial support to maintain OptiBoard for all members to enjoy.
Once again, you are singling out a ZEISS product in the context of your own.I know, from a personal view, that some times Creation works better than Individual.
I agree that submitting "bad" position of wear measurements can negatively influence optical performance. However...I guess this is because of wrong measurements of the Individual, but if that is the case, it will only confirm that some measures are dangerous to measure when you cant do it well enough, and because the measurement are not fixed.
Wearer preference is not based solely on the presence or absence of position of wear measurements. There is every possibility that some progressive lens wearers may simply prefer the Creation lens design more, particularly when optical customization is less significant, although I have seen evidence from independent clinical studies to suggest otherwise.
Also, optical performance is no more sensitive to position of wear measurements, and in some cases even less sensitive, than it is to any other fitting measurement, including the PD and fitting height.
Yes, you can negatively influence optical performance by supplying the incorrect position of wear measurements, just as you can negatively influence performance by not measuring PDs or fitting heights correctly. But you continue to fail to realize that submitting incorrect position of wear measurements will not impact optical performance any more than not submitting position of wear measurements when there is a comparable difference between the geometry of the fitted lenses versus the geometry of the refracted lenses.As I say ones again, Individual is not a bad lens, but to get back to my point, Vertex and panto is not FIXED values and are nearly impossible to measure correct
But, more to the point, wouldn't your patients be better served by learning to take these position of wear measurements more accurately rather than by resorting to traditional lens designs based on technology that hasn't changed fundamentally in over 50 years?
Yes, I got the impression that you two knew each other. His last few posts, however, have made no mention of recommending any lens other than Shamir products.Actually I know Peter from the thread above, but he are selling not only Shamir lenses. He are, as I know, selling both Zeiss, Hoya and Essilor as well, but his statement is actually very relevant in this thread.
Last edited by Darryl Meister; 01-03-2010 at 05:19 PM.
Darryl J. Meister, ABOM
post
Last edited by Mr.Powers; 01-05-2010 at 01:55 PM.
[QUOTE=OCP;325693]First off, I do not sell Zeiss lenses but found this question by Darryl to be quite interesting, yet you failed to answer it once already (oversight?). Now you acuse us of all being "pro Zeiss", which I can assure you is hardly the case, but we are here to learn the differences in all lenses.
So, is in fact, the Autograph lens re-designed for all the measurements or just simply power compensated. A simple Yes or No works here, and adds immensely to your credibility in this debate, as otherwise it's just inuendo. Step up, or move on.
That was certainly how I interpreted your comments in the new thread, which essentially rehashes half of this thread. Allow me to quote you:
...agree that Individual, theorethical and hypothetical, could be the best lens out there, but thats because we are only familar with the data we read on the paper from the manufacturer... In the name of evolution, the manufacturer will keep on invent new "histories" to sell new lenses and to provide new and more complicated data to produce the lenses. In my opinion this is mostly bulls***... (-and I claim Shamir are handling the abberations best :D and we don´t tell imaginary stories as well)
I do agree, however, that Carl Zeiss Vision has provided a lot of "data on paper" for Individual. I would encourage all manufacturers to fully disclose the features of their products by making the necessary substantiation of their product claims available to eyecare professionals so that they can make a well-informed purchase decision.
Mike, please feel free to attempt to find another thread on OptiBoard started by a "pro ZEISS" person that promotes a ZEISS product, makes disparaging remarks regarding the performance of a non-ZEISS product, misrepresents optical principles to support a ZEISS product, etcetera.
Again, it would be best for you to provide (e-mail or PM is fine) the name or location of your laboratory. I would be happy to make the appropriate ZEISS representative in your region aware of your situation.
Unfortunately, if you have had non-adapts with 14 out of 43 Individual jobs, it is unlikely that you will solve the problem simply by reading OptiBoard posts. This is indicative of a significant issue that will probably need to be addressed in person or resolved at the laboratory level.
Further, if you do indeed want to continue selling ZEISS lenses, but are concerned about taking position of wear measurements, GT2 3D should be available in your area. This is a customized lens that does not require position of wear measurements. And, of course, traditional ZEISS progressive lenses are also still available.
Darryl J. Meister, ABOM
still like to hear from somebody, about my last post !
Since this thread has unfortunately degenerated into a lot of "us versus them" bantering that is unnecessarily focused on specific products, I wanted to do my part to get this back on topic.
Product endorsements aside, Mike's (OCP's) contention, at least as I understand it, is essentially that position of wear measurements cause more trouble than they are worth because:
1. These measurements are difficult to measure accurately.
2. Bad measurements can negatively influence optical performance.
3. These measurements may change because they are not "fixed."
His conclusion seems to be that you are better off selling lenses that do not rely on position of wear measurements or that at least rely on some simplified version of these measurements.
Mike, please correct me if I have misunderstood any of these points, before I continue.
Also remember that no free-form lens supplier requires position of wear measurements. Even Zeiss Individual can be ordered without them, resulting in a lens design that is optically customized for a "default" position of wear, if you would prefer not to take these measurements.
Darryl J. Meister, ABOM
Hi Darryl.
Your three point seems correct.
Vertex and Panto is the questionable measures here, and because these measures do not noticeable impact the optical result, I suggest the industry use default or simplified these two measures. I will explain ones again, why these two measures should be simplyfied, or removed, and why they are not fixed values.
Panto: You change head angle many times a day and your eye does not move vertical on a line, but from the same attached point. That will change the angle. Panto value are normally from 5-15 degrees, and therefore it would be more logical to use only 3 parameters for this, lets say 5-10-15. Then you can only go 2-3 degrees wrong and 2-3 degrees will not impact the optical design at all.
Vertex: You or someone else said that 13½ mm vertex was more correct than 13 mm. That statement is again only theoretical because the groove can easily move the lens 1-2-3 mm back or forwards. Only very few can measure this value 100 % correct. It´s nearly impossible. We know, that if you dont have the refracted AND the fitted vertex you cant make POW compensation, but you can always make design compensating (design compensation does not include power changing in the vision area. Only in the abberations zones), but again this is more theoretical in my opinion. The manufacturer will always seek the best optical solution, and that include large vision area on near, intermedia and distance, so my point is, if you with 13½ mm vertex can make the best possible design with the largest vision area, why dont use that design in 10 mm Vertex as well.? It´s not logical not to use that design no matter what the Vertex are. I know you can increase the astigmatical deviation if you put the lens closer to the eye (and I must think that is what happens), but if you measure wrong, lets say you measure 7 mm and in real life after glazing etc, the Vertex are 13 mm, then the client would actually get a harder design than they are used to and therefore get adaption issues. I´m quite sure this is the most frequent reason for adaption issues. Normally vertex distances goes from 9-15 I think. By using default (12-13) you will mostly only have 2-3 mm wrong vertex, and 2-3 mm wrong Vertex does not influence the design noticeable at all.
When saying that it´s only a question about education, this is a truth with modifications. When using only a few parametres here, you can actually simplify the tools for the measurements and then you don´t need the education in the such a degree.
I hope this ones again could clear out my stance on these two parameters.
And please. When I say "you" I nessasary dont meen Individual or Zeiss. I´m talking about the industry in general. But you are representative for Zeiss so it will be more accurate to talk to you about Individual. I´m not bashing your product at all. Only talk about it.
Mike
[QUOTE=obxeyeguy;325705]Instead of just looking for something to blaim me, you could start to join the debate with some constructive informations.
Where did I blame you for be a Pro-Zeiss member ? Cant you read, or at least read between the lines?
This is not a debate about what Zeiss or Shamir are doing right or wrong.
Mike
[QUOTE=OCP;325748]Another typical response, but still no answer. Throw it out, see what sticks but nothing to back it up.
[QUOTE=obxeyeguy;325753]You do not realy get it, do you?
Why do you want a answer from me of something I find silly.?
Why dont you ask your Shamir representative if this is so important for you?
Why dont you bring something informative to this debate instead of trying to drag me down.? You can´t.
Mike
In the name of evolution, the manufacturer will keep on invent new "histories" to sell new lenses and to provide new and more complicated data to produce the lenses. In my opinion this is mostly bulls***... (-and I claim Shamir are handling the abberations best :D and we don´t tell imaginary stories as well)
Wow are we really claiming that Zeiss does not provide accurate data? I personally wish that all manufaturers includeing Shamir released white paper such as Zeiss. I would go so far as to say Zeiss's white paper could be used as a template for other companies since it is often thorough and contains all information necessary by me with exception to the stuff that would probably be overkill. Darryl once again I appreciate all your company has done and will do to provide accurate and concise information, I tend to go searching for information and I am sure I don't have to tell you it isn't easy to come across. Once again let me reiterate, the Zeiss Individual is a top notch lens and despite what the Shamir fans opening and inserting foot in mouth I think the Auto II is the same.
Someone likes white paper, others never read it. I agree that if someone read it, the white paper from Zeiss is a great one even though it is technically and theoretical stuff.
My english is not great as other here, so I apologize if someone got that understanding that I wrote that Zeiss not provide accurate data. (even I cant see why someone got that understanding). Please try to bear with our overseas different language, thanks. I prefer to debate with you, in spite of language issues, instead of just shut up. We are all here for learning, and excuse me, I think there is plenty of room here for both mathematician, and optician wholesaler with controversial stances.
That makes it just more funny to join. :cheers:
Mike
I used to share your observations about pantoscopic tilt, Mike.
But then, this forum and Darryl & Laurie in particular set me straight:
Panto is NOT about head/face angle. It's about determining how to best ensure the design pole of a lens intersects the center of rotation of the eye.
Therefore, it's about ensuring that a client's head/face plane is in an erect position (NOT the habitual position of the client's head or facial plane posture, and not the various head angles that a person sweeps through posturally in a day. That's taken care of when it's all lined up properly with the CR).
As far as vertex - for me it's about the larger deviations from default values and how it effects apparent FOV (field of view). I would expect an advanced design would incorporate this value into their DV optimzation...regardless of power.
FWIW
Barry
Last edited by Barry Santini; 01-04-2010 at 08:12 PM.
[QUOTE=OCP;325807]Mike, I'm sure you are a very smart guy, but the way you come across is your way or the highway, nothing else. Go back and re-read some of you own posts, and whenever you get questioned on anything, all we get is a song and a dance.
Oh, buy the way, as I find it to be very relevant to the conversation, as maybe others do also, the question still stands.
(insert cocky response here)
Strike three!!
Last edited by obxeyeguy; 01-04-2010 at 07:51 PM.
Hi Barry.
About Panto you are so right.
"Panto is NOT about head/face angle. It's about determining how to best ensure the design pole of a lens intersects the center of rotation of the eye."
BUT if you move your head a littlte bit up and down, you change the result of the measure!
SO the Panto is only a average measure where you presume this is the avarage head position for your client.
Now we are back to where we startet. Many of us are always seeking to make the best possible lens for our client, by taking a lot of measures (that many times goes wrong) and some of these measures are actually only average values. Thats why I suggest to standardise these mesurements to avoid wrong measurements. I tell you that the Panto tilt is very, very difficult to measure correct for many reasons. The client do not always stand normally with relaxed head position, and the tools you use to measure the result is inaccurate.
Mike
[QUOTE=obxeyeguy;325843]Well I only defend my right to disagree with the majority in a issue that most of you was not aware of.
Mike
I'd like to verbalize the assumptions I understand are currently being used to determine pantoscopic tilt:
1. The goal is to get the design (reference) pole of the lens being fitted to intersect the CR of the eye. In the case of best form fitted, spherically-based, corrected-curve lenses, the OC and the *design* pole are one and the same. Therefore, Martin's rule of tilt (which assumes a vertex distance I believe, of 13.5 to 14mm (27mm to the CR) applies when fitting these lenses.
2. A method of measuring pantoscopic tilt starts with the client's facila plane in an "upright" position. To determine the facila plane, iimagine a line drawn from the upper orbital bone to the lower orbital bone, and continue downward to the plane of the teeth and chin. In many cases, the points described will not lie all in a single plane. So you average.
3. Client preference in frame fitting will further help to determine the final anle of the frame/lens plane. So eyewear should be pre-fiited as much as possible *before* a measurement is made.
4. Ear height and habitual head or nech posture should only influence your placement of multifocal lenses, bifocal, tri, or progressives, depending on the "in-situ" resultant frame fit and plane. This should not and does not influence the results of 1, 2, or 3.
So yeah Mike, It's a fudge. And I'm here to say the my own overwhelming success with Auto II SV, which does NOT require Panto, Vertex or FF (within a range up to 8 degress I believe) values, is a testament to the simplified fitting process. My only complaint with Shamir is that they don't clearly compose, explain and communicate the proper fitting instructions for Auto II SV.
So What would I like beyond the simplicity of Auto II SV? I'd like the ability for some fits, as Individual SV allows, to specify the specific Base Curve to be used. In this way, I get the lense plane to match the frame plane, and the fit of the eyewear is more correctkly ensures, particularly with the nutty zyl frames being made today.
Further *constructive* discussion...from anyone...
Buelller?
Barry
Hi Barry
Without being 100 % sure, I think the strategy from Shamir, accordance to SMART SV, is to use this lenses for normal frames (frame angle up to 8 degree) and use the Attitude family for curves more than this.
SMART SV, with standard measures, is really a great succes.
Anyway, I agree that it would be desirable if we could order SMART SV with FaceForm angle as well.
About the panto tilt I do not, in the theory, disagree with you. We are back to the beginning again, where it´s nearly imposible to measure this tilt perfect every time. This only confirm the need for a more easy way to measure the angle, and three different values is actually enough, to get a acceptable result. With SMART SV you have a great succes with only one value. -and a standard one as well.
Mike
Last edited by OCP; 01-05-2010 at 02:28 PM.
Mike, let me address your three concerns individually, although I will be repeating myself in most cases. Unfortunately, there are several principles that you still do not seem to understand clearly. Hopefully, this post will clarify at least some of these misconceptions.
As Barry reiterated, pantoscopic tilt does not change with either head or eye angle. Panto will only change in a finished pair of eyeglasses if the actual position of the eyeglasses on the face is physically moved. You are mistaking the angle that the lens makes with the line of sight at different viewing positions for the pantoscopic angle used in lens design calculations, which is actually used to predict the angle of the line of sight at these positions.Panto: You change head angle many times a day and your eye does not move vertical on a line, but from the same attached point. That will change the angle.
It is does not follow (that is, your argument is non sequitur) that it is "more logical" to use only 3 pantoscopic tilt options. Even if we assume that an error of 2.5 deg is acceptable, you are still no more likely to choose the best option of the 3 available angles unless you can estimate the angle of tilt within 2.5 deg in the first place. So what have you gained?Panto value are normally from 5-15 degrees, and therefore it would be more logical to use only 3 parameters for this, lets say 5-10-15. Then you can only go 2-3 degrees wrong and 2-3 degrees will not impact the optical design at all.
I will provide you with a very clear example: If you can only estimate this angle within +/-4 deg, for instance, and the real value is 5 deg, you could still potentially guess "9 deg" (5 + 4 = 9). You would then choose the 10 deg design option, which is still 5 deg off from the best design option (that is, the 5 deg design).
In fact, if you can take these measurements accurately, you are only increasing the likelihood of an error, since you have an inherent rounding error of up to 2.5 deg from the exact value.
I also noticed that you didn't mention wrap, although the optics of progressive lenses similarly affected by both pantoscopic tilt and face-form wrap. Further, only lens designs that are truly optimized for the position of wear will adequately address the effects of either type of lens tilt.
I agree that taking these measurements accurately does indeed involve a "learning curve" for many opticians. Of course, taking PD and fitting height measurements accurately also involves a learning curve for new opticians.1. These measurements are difficult to measure accurately.
Those eye care professionals who want to offer their patients the best vision quality possible will be more willing to embrace these new technologies, even if they require additional training.
Further, new tools are becoming available every day that allow eye care professionals to take these measurements with greater accuracy and increasing ease.
Again, taking "no" measurements will often result in the exact same errors in optical performance compared to taking "bad" measurements.2. Bad measurements can negatively influence optical performance.
Most of these measurements are indeed fixed, at least to the extent that the patient wears his or her eyeglasses in roughly the same place on the face. As I mentioned above, you have simply misunderstand the application of pantoscopic tilt in lens design.3. These measurements may change because they are not "fixed."
As I have already explained, it does not matter whether you can measure this or any other position of wear value to an accuracy of 100%. Unless you are completely off in your measurement, you will still arrive at a value that will often be closer to the actual value than you would obtain by ignoring this measurement entirely.You or someone else said that 13½ mm vertex was more correct than 13 mm. That statement is again only theoretical because the groove can easily move the lens 1-2-3 mm back or forwards. Only very few can measure this value 100 % correct. It´s nearly impossible.
In simpler terms, your argument isn't entirely unlike saying that, because someone isn't necessarily very good at his job, he shouldn't bother working at all. Unless you are so bad at your job that you are actually doing more harm than good, you'd probably want to earn a living though.
You still don't seem to comprehend the difference between compensating a prescription for vertex distance versus optimizing a lens design for the vertex distance associated with the position of wear, which I have already attempted to explain to you several times in this thread.We know, that if you dont have the refracted AND the fitted vertex you cant make POW compensation
You are only making a conjecture here. And it is incorrect. Optimization for the position of wear primarily influences the "vision area," not the "aberration zones." In fact, there is no reason to attempt to nail down the exact prescription for the position of wear within the peripheral zones of a progressive lens because they are aberrated.but you can always make design compensating (design compensation does not include power changing in the vision area. Only in the abberations zones), but again this is more theoretical in my opinion.
I agree that the final lens will never be any better than the best example of the basic lens design (that is, garbage in = garbage out). Customization for the prescription and the position of wear simply preserves the intended optical peformance for each wearer, even if that optical performance is mediocre in the first place.It´s not logical not to use that design no matter what the Vertex are.
Let's assume for the sake of argument that could indeed make such a gross measurement error. There is also every possibility that the lens could be fitted a vertex distance of 7 mm, while the semi-finished lens design may have been optimized for an assumed vertex distance of 13 mm, leaving you in the exact same position.but if you measure wrong, lets say you measure 7 mm and in real life after glazing etc, the Vertex are 13 mm, then the client would actually get a harder design than they are used to and therefore get adaption issues.
Then, by necessary extension, you must also agree that accurately optimizing a progressive lens design for these measurements should improve adaptation.I´m quite sure this is the most frequent reason for adaption issues.
I think that you have chosen an aribtrary range of numbers (9 to 15) based upon your desire to support your belief that you will never be off more than 2 to 3 points from some average value (12 mm), not upon vertex measurements from an actual population of wearers, which can vary significantly based upon the frame size, facial features, prescription, etcetera.Normally vertex distances goes from 9-15 I think.
Nevertheless, I agree that the use of judiciously selected "averages" for the position of wear is preferable to taking no measurements at all or to taking measurements that are grossly inaccurate. But I also believe that eyecare professionals are more than capable of taking measurements that are reasonably accurate.
But they do at least have the choice when a white paper is available. Not everyone reads the nutrition information labels on the food they buy, while many feel that these labels provide very important information.Someone likes white paper, others never read it.
Last edited by Darryl Meister; 01-05-2010 at 11:49 PM.
Darryl J. Meister, ABOM
Hi Darryl
If you measure panto with the Infral, would the result be equivalent no matter how the patient a standing with their head?
You say that opticians are more than capable to measure Panto and Vertex. This is conjecture as well. Everyone reading here, try to let different opticians in your stores take these measures. I will promise, that you will all get different results, and sometimes the result will be very long away from "reasonably accurate".
I do not know your skills in US, but in Denmark, where we have 4½ years of education, it´s a problem. I´m quite sure the same issues is seen in other countries.
If Panto and Vertex was fixed, the tools to measure these values should be good enough. You claim that they are not and we will se new and better tools. Why? A fixed value is very easy to measure.!
"You still don't seem to comprehend the difference between compensating a prescription for vertex distance versus optimizing a lens design for the vertex distance associated with the position of wear, which I have already attempted to explain to you several times in this thread. Optimization for the position of wear primarily influences the "vision area," not the "aberration zones." In fact, there is no reason to attempt to nail down the exact prescription for the position of wear within the peripheral zones of a progressive lens because they are aberrated."
You read me wrong. Vertex design compensating DO influence the vision area, but not the POWER in the vision area. Pow. compensation is only when you got the refracted Vertex as well. If the Vertex is very short, lets say 7 mm, then it´s acually possible to increase the vision area by increasing the CYL/SPH abberations in the peripheral zones. Thats a fact. Anyway it works great in the theory, because if the Vertex is not 7 mm in real life, but lets say 10 mm or even more, the increased Cyl. Abberations could actually make a worse design than the client are used to.
Everyone here: Please understand that this dialog is not because I´m stubborn (Darryl could just as well be that), but Darryl has a great reputation here and many consider Darryl as the great optical guru, as he certain are in many cases. For me, I look just more and more opinionated, and I know that. I´m alone in the wrong class where everyone agree with the "teacher", and not strong enough to just ignore this thread. Lucky me we are thousandth kilometre from each other, otherwise you would all beat me up in the schoolyard.:hammer:
Mike
Last edited by OCP; 01-06-2010 at 11:54 AM.
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