Issues with fitting hyperopes with "individualized" PALs

[musicvirtuoso]

(I have another post that is directly related to this but am rerouting it to here) Below are the posts that started this thread (followed by my response):

... As I recall, a lot of these patient idiosyncracies were to be taken care of with the Varilux Ipseo lens, and the measurements were taken care of.
I really had no success with hyperopes with that lens, which I still think is a bit odd. That's my one cent!...

Very interesting that you put that... I recently posted a question about problems with hyperopes in the Zeiss Individual in the PAL category of the forum ... maybe the problem is similar?

I don't think I can respond to the Ipseo v. Individual conundrum, inasmuch as I only fit a handful of Gradal Tops and GT2s with no patient complaints. As with all lenses, I tried these lenses on both myopes and hyperopes, with a few established patients thrown as a control.
My problem with "individualized" lenses is this: the lens manufacturer plays a game of "musical base curves" or "pin the tail on the power", which is not always in the patient's best interest. If you had any experience with the Ipseo, you know that it came from the lab with different powers than originally prescribed to meet the patient's individual needs, supposedly, and you verified the lenses using a decimal scale, instead of quarters and eighths. Sometimes the lenses had "mystery prism", once again to match the patient's head movement. Often, this gave the hyperope a tiny reading area (even with a +1.75 Add) that was quite disconcerting. (Full disclosure: I didn't know what was happening there until I reviewed prism thinning, and the dos and don'ts.) Needless to say, I let the Ipseo go after giving it a good road test. It was OK for myopes, but not hyperopes, generally.
Does the Individual have the same sort of characteristics? Does it work for myopes?

The Individual works wonders for myopes (especially those with lower powers). We are made to believe that the lab is properly compensating for the measurements that we give them (e.g.: VD, Tilt, Wrap, etc.) - and that these compensations are working for the benefit of the wearer. Am I naive to believe they are actually doing this? You are implying that they apply random BCs and power adjustments and cross their fingers in hopes that it will work. I guess I'll have do my own reviewing of prism thinning to get a feel of what's going on here. It's frustrating, especially because we really don't see these kind of problems with the Gradal or GT2.

[musicvirtuoso]

Rerouted from parallel thread:

I believe that Zeiss is currently tweaking the Individual algorythm to shorten the applied corridor length.
My failures have been all about too much depression

B

Are you saying that the corridor is too long? If so, wouldn't this be seen in myopes as well? And wouldn't there be ways around this problem? Maybe I'm misunderstanding...

[uncut]

Rerouted from parallel thread:



Are you saying that the corridor is too long? If so, wouldn't this be seen in myopes as well? And wouldn't there be ways around this problem? Maybe I'm misunderstanding...

Easily add +0.25 to ADD for all "PRISM-THICKENING LENS COMPANY'S" lenses post Gradal HS....a workaround.

[OpticalMessiah]

My biggest concern, which I didn't explain well enough, is that the PAL manufacturers are designing these "individualized" lenses without our input. This is particularly true with respect to base curve and center thickness, as it relates to our "garden-variety" hyperope, if you will. Early on in my career, I didn't really notice that problem with lenses like the Varilux II or Varilux Plus. I fit those lenses on several hyperopes with a high level of success. As time went on and lenses developed more asphericity, I found myself requesting a steeper base curve than the manufacturer/lab recommended to heighten patient compliance. The steeper base curve created more magnification; the patient was happy with the resulting acuity. As I remember, that happened a lot in the Infinity/Comfort days. (Full disclosure - I did receive honoraria from Varilux on a few occasions, but I was never a "***** for Essilor.") This was a time when PALs were readily available in the familiar +2, +4, +6 and +8 base curves, very similar to SVs and MFs. I don't mean to sound "old-fogey", but I liked that time frame (pardon the pun). In the present day, there has been a complete "paradigm-shift" in lens design. Flatter, thinner, and lighter are the buzz words. High-index lens indices have gone from the 1.6 spherical to the 1.74 aspheric. It's a myope's paradise; the hyperope surveys a wasteland. That's a shame. Lens design seems no longer necessary. The manufacturer now bypasses the lab and creates a lens using technology that is very exciting, but hard to understand and impossible to explain to the patient without using trigonometric functions. It seems like we know little about how it works; we just expect the patient to be compliant. Gee, I feel like I'm standing on a soapbox. Sorry about that! My point, and I do have one, is that the hyperope seems to be all but forgotten. Luckily, the industry continues developing a back-surface PAL that should be of benefit to both myopes and hyperopes. I'm not a real big fan of Definity, but I like the back-surface idea itself. I've been out of the loop for a few months, decompressing, so I don't know what stage that design is in at present. I do hope that the supposedly spherical front surface allows for some deviation in curvature, for hyperopes. Wow, that was more a history lesson than a reply! I'm so used to talking to students that I sometimes forget about relating to colleagues. I apparently need more decompression.

[musicvirtuoso]

You don't sound preachy at all. I really appreciate your input. As I really haven't been doing this long (only about 5 years), I can really benefit from other people's experience. So basically, I'll just have to wait for them to come out with a re-worked design or just not use that lens? The unfortunate thing is that the place I'm at now only uses Zeiss lenses. Now, I like Zeiss and all, but I agree with a lot of people's opinions on here when they say that there is no "one-size-fits-all" kind of lens. We've done well with the Gradal and GT2, but in these cases (when these "individualized" lenses are pushed to the pt) it would be nice to have other options.

By the way (and asking this makes me feel stupid), do you think if there was a way we could manipulate the BC so it's a little steeper, it would help the hyperope, especially in this lens?

[OpticalMessiah]

On your question about whether or not to use the Individual, I've been an "optical thrillseeker" for a long time now, so my first impulse would be to try it out and see if the patient is compliant. Are these patients established, or are they new to the practice? That's an important question, because it's helpful to know the patient's compliance with previous Rxs and previous lenses. When you don't have that information, you're at a disadvantage. Examining the patient's current glasses (lens design, center thickness, base curve) is helpful. Measuring the base curve on an aspheric lens is tough, but if you can get a rough idea, it's better than none.

I was told a few years ago that it will become necessary to read the curves on the back surface of the lens to aid in compliance, but I don't necessarily think that is true, at least not yet.

Whether or not it is wise to wait for a design to change, if you don't know how it works now, how will you know when a change is required? As Barry mentioned in a previous post, manufacturers find out about problems and make the required tweaks. As long as you know about the tweaks, you're in good shape. That's the beauty of working with one lens manufacturer. Your rep should have this knowledge. Use him/her to keep you updated.

About hyperopes and steepening the BC, that's a tough question with this technology. Oftentimes you don't have that option. If you do (your rep should know), be cautious. If your patient does a lot of driving (outside sales, for example), he/she might appreciate that. Here again, find out what your patient is accustomed to with respect to BC and CT, and that information will help you make that decision.

Always use your patient's best interest as your guide. Then you'll have a compliant patient who will be returning for your guidance next time.

[AWTECH]

My biggest concern, which I didn't explain well enough, is that the PAL manufacturers are designing these "individualized" lenses without our input. This is particularly true with respect to base curve and center thickness, as it relates to our "garden-variety" hyperope, if you will. Early on in my career, I didn't really notice that problem with lenses like the Varilux II or Varilux Plus. I fit those lenses on several hyperopes with a high level of success. As time went on and lenses developed more asphericity, I found myself requesting a steeper base curve than the manufacturer/lab recommended to heighten patient compliance. The steeper base curve created more magnification; the patient was happy with the resulting acuity. As I remember, that happened a lot in the Infinity/Comfort days. (Full disclosure - I did receive honoraria from Varilux on a few occasions, but I was never a "***** for Essilor.") This was a time when PALs were readily available in the familiar +2, +4, +6 and +8 base curves, very similar to SVs and MFs. I don't mean to sound "old-fogey", but I liked that time frame (pardon the pun). In the present day, there has been a complete "paradigm-shift" in lens design. Flatter, thinner, and lighter are the buzz words. High-index lens indices have gone from the 1.6 spherical to the 1.74 aspheric. It's a myope's paradise; the hyperope surveys a wasteland. That's a shame. Lens design seems no longer necessary. The manufacturer now bypasses the lab and creates a lens using technology that is very exciting, but hard to understand and impossible to explain to the patient without using trigonometric functions. It seems like we know little about how it works; we just expect the patient to be compliant. Gee, I feel like I'm standing on a soapbox. Sorry about that! My point, and I do have one, is that the hyperope seems to be all but forgotten. Luckily, the industry continues developing a back-surface PAL that should be of benefit to both myopes and hyperopes. I'm not a real big fan of Definity, but I like the back-surface idea itself. I've been out of the loop for a few months, decompressing, so I don't know what stage that design is in at present. I do hope that the supposedly spherical front surface allows for some deviation in curvature, for hyperopes. Wow, that was more a history lesson than a reply! I'm so used to talking to students that I sometimes forget about relating to colleagues. I apparently need more decompression.

Your concern about base curves is based on historical issues. Not all digital lens do allow for this, but it is possible to get almost exactly the same vision with different base curves using digital surfacing. The reason is simple: Light enters a material at a certain angle and based on the curve of the front and rear, index, thickness etc. the departing angle is detemined. Now change the front curve and make a compensating adjustment to the back surface, (digital surface not spherical) and you can have the light path be the same.

[Barry Santini]

Your concern about base curves is based on historical issues. Not all digital lens do allow for this, but it is possible to get almost exactly the same vision with different base curves using digital surfacing. The reason is simple: Light enters a material at a certain angle and based on the curve of the front and rear, index, thickness etc. the departing angle is detemined. Now change the front curve and make a compensating adjustment to the back surface, (digital surface not spherical) and you can have the light path be the same.

I agree. But for a few individuals, the change in magnification/perspective can still cause some adaptation problems.

B

[AWTECH]

I think those adaptation problems are a result of the appication of the basic theory that I explained. That is, the management of light is not truely optimized for those situations where the patient is experiencing the issue.

Another possible reason is the refractration error from ideal is then causing the calculations of the surface to be off slightly. We can make a lens much more accurately than we can get a refraction. (Not just the fault of the doctors, but often due to the dynamics of change within the human eye that we are not able to manage with a refraction or a lens.

[OpticalMessiah]

Clearly (pardon the pun), we are all looking to manage light efficiently, and functionally, for the patient. Because of that search, the people in lens R&D develop new topographies to respond to efficiency and functionality. This new lens architecture, if you will, always begins with a theory. Applying the theory doesn't always lead to a practical response from a patient. Patients are human beings, first and foremost. Hyperopes are a particular type of human being. Hyperopes, theoretically speaking, should be "perfect" candidates for progressive lenses. Yet, not all of them are. Not yet anyway.

Why is this? That's a difficult question to answer. Probably the best explanation could be gleaned from individual patient responses to their non-compliance issues. (I don't like the term "non-adapt"; I haven't used it in probably 15 years.) Having heard hundreds of these testimonies, the most prevalent problem has to do with a drop in magnification due to the lens design itself. As I told musicvirtuoso, my typical treatment would be to raise the base curve. A few times I would change the design to a lens that I knew had a slightly steeper BC. (That doesn't exist anymore; everything is flatter.) Either way, the patient felt that his/her vision was optimized because I was able to replace some of the mag that they lost. Thanks for agreeing with me on that, Barry.

It goes without saying that refraction is not always accurate. The accuracy often comes from the clinician interpreting the findings of the phoropter. Auto-refractors are very impressive, but I still don't think they surpass a doctor's judgment. (I was also going to say something about how many optometry students view refraction, but that's not germane.) Turning a refractive finding into a lens creates a myriad of outcomes, particularly when we factor in: lens material/index, curves on front and back surfaces, orientation of the OC, etc. Luckily, we have enough knowledge of these variables to dispense a pair of glasses with reasonable surety of compliance. But, my question remains the same: What control does a dispensing optician have over the variables I just mentioned in a free-form lens? For the patient, is it WYSIWYG?

BTW, Allen, of course my concern is based on historical issues. I've been dispensing glasses for more than half my lifetime, so in a sense I'm historical myself! Or is it hysterical? It's one of those! (I wanted to end with a little comic relief.)

[musicvirtuoso]

I agree. But for a few individuals, the change in magnification/perspective can still cause some adaptation problems.

B

Clearly (pardon the pun), we are all looking to manage light efficiently, and functionally, for the patient. Because of that search, the people in lens R&D develop new topographies to respond to efficiency and functionality. This new lens architecture, if you will, always begins with a theory. Applying the theory doesn't always lead to a practical response from a patient. Patients are human beings, first and foremost. Hyperopes are a particular type of human being. Hyperopes, theoretically speaking, should be "perfect" candidates for progressive lenses. Yet, not all of them are. Not yet anyway...

... BTW, Allen, of course my concern is based on historical issues. I've been dispensing glasses for more than half my lifetime, so in a sense I'm historical myself! Or is it hysterical? It's one of those! (I wanted to end with a little comic relief.)

Thank you! This is type of conversation I was looking for. I think I will see if manipulation of the BC is going to help (given I'm able to do that in this lens). I will also be following up with Zeiss to confer with them.

[Robert Martellaro]

Rerouted from parallel thread:



Are you saying that the corridor is too long? If so, wouldn't this be seen in myopes as well? And wouldn't there be ways around this problem? Maybe I'm misunderstanding...

Yes, that's what he's saying. It should be more of a problem for moderate to strong myopes compared to hyperopes, due to the image displacement from prismatic effects. Hyperopes would probably do better with wider zone widths due to magnification. From my experience, myopes are less sensitive to changes in Rx, surface design, and curvature, possibly because of differences in retinal image size, and from wearing eyeglasses for a larger percentage of their lives compared to hyperopes, and the ability for stronger myopes to peek under their lenses to see very small print.

[OpticalMessiah]

The length of the corridor, and the progression of power within the corridor, were issues that were dealt with quite well in conventional PALs in the '90s. Hyperopes were helped with the faster progression, inasmuch as there was less "head-bobbing" with these designs. Myopes befitted to, but to a lesser extent. The shorter corridor led to the development of "short-corridor" PALs (naturally!), which are/were my least favorite choice for hyperopes (with the possible exception of the Shamir Piccolo).
In practical terms, the Add cut-off point for hyperopes would be +1.75, after which the patient would notice the intermediate range loss, suggesting the need for a longer-corridor lens, which would include the intermediate range. Here again, myopes didn't necessarily have this restriction.
I agree completely with Robert in his comparison of hyperopes to myopes. Myopes are certainly less affected by differences in front surface curvature from spherical to aspheric because the lens typically flattens less than 2D. The same design change for hyperopes can be as much as 4D. Does that same amount of difference exist in digital lens constructs, or can it be corrected with multiple prismatic applications?

[Georg Mayer]

Coming back to the question if a desgin which works wonders for myop patients is not really at it's best for hyperobs.
Exactly for this reason we differentiate and offer our ILT myop and an ILT hyperob, their range overlapping slightly to cover cases with anisometropia being able to get both lenses with the same design.

Georg Mayer
Rodenstock - Munich
Germany

[rdcoach5]

I had a similar problem with a hyperope describing blinding glare for night driving. Orig lens was Definity made 2 years ago. After Essilor re-designed the Definity she bought another pair in the exact same Rx and experienced the glare at night issue and decreased near vision. She said she had to look down farther. The base curve on the older "good" pair of Definity lenses was steeper. My lab called and no, you cannot specify a base curve for Definity. Next, we tried a glasses check with the Dr and no change. Then we tried Zeiss Individual and it was slightly better for glare but still not as good as her orig. Definity. Finally, after consulting with Optiboard on the night glare issue, we re-made the Rx in Definity 1/4 diop less plus and the issue was solved. I think we used the short corridor but I will have to check when I get to the office.

[OpticalMessiah]

Thanks, rdcoach5. I really appreciate a practice example. In many ways, it trumps the theoretical, particularly in this case. (In truth, I love the theoretical, too, but if you could ignore that right now, I'd owe you one.) I'd like to know more about the Rx: distance powers @ 90, Add power, Panto (did you increase it for the new Rx?) and any vertex changes from the old frame to the new. Lastly, did you change the fitting height at all when you went from conventional to short corridor (I'm guessing that intermediate usage wasn't an issue)? Sorry about all the info requested. I'm naturally nosy about these things, especially with hyperopes.

[snotbagel]

I had much the same response by hyperopes to the new digital lenses. Why..whats different? Well, first off, they are not getting as much magnification, even though the image may be sharper. Also, base curves may be bit steeper, since the entire front surface is providing the near power. We also have no idea of how much inherent prism is changed by the corridor placement, and on and on.

So, I have found great success with Shamir element and Pentax perfas prime for hyperopes, when compared to my other favorite digital lenses. I cannot say why, I'd probably need an engineering degree to understand it. Practically speaking, the only reason I'm using digital lenses for these patients is an aversion to the very idea of molded progressives ( I see all those stacks of lenses, sorted by bc and add power, material, etc..millions of $ sitting on a shelf.makes me shudder.)

[One science]

You may be a little bit naive. Before choosing try to document more about the details, pay attention to the references. There are many PAL manufacturers that are designing so called "special" lenses without an input from the real specialist.

[DCrespo]

Personalized lenses usually are back-surface progressives that are cut with digital technology on spherical fronts. With back-side PALs, base curves are usually selected as flat as possible, so the near region is almost plano-convex. In this case, for hyperope wearers the curvature of the concave side (the free-form side) on the near region tends to be very small, and this results in the end in poorer optical perofmance.
With the curvature of the back surface being so small in the near region, the effect that a personalized lens can have to improve near region performance is very limited. A free-form lens can be computed with local changes in the surface that can improve visual acuity for a particular combination of prescription, base curve, tilt, wrap, etc. This is a personalized lens. But the effect of local aspherization to improve visual acuity is smaller when the surface is flatter, that is why a back-side personalized lens can be not so good for hyperopes on the near region.
Possible solutions are to use a steeper base curve, or to use a personalized progressive that has a progressive front side. Some products from Essilor and Zeiss are like this.

[WFruit]

The best results I've found, using both Seiko and Shamir Free Form designs (both of which use completely spherical front curves) is to base the base curve (horrible pun) for myopes on their distance power, and for hyperopes on their total reading power (not just the add power). It works a little bit better for Seiko than Shamir as Seiko is more leinient in letting you choose your base curves, although Shamir tends to like steeper base curves in general. Usually I will let the software pick the base curve for myopes and it does a very good job. For hyperopes I'll bump the base curve up a diopter or two, depending on the exact Rx.

For Hoya and Zeiss Free Form lenses, they both modify the front and back curves, so I'm less certain whether or not this will work as well with their lenses. If someone can prod Darryl Meister from Zeiss to take a look at this thread he should be able to shed some insight as well.

[Darryl Meister]

Very interesting that you put that... I recently posted a question about problems with hyperopes in the Zeiss Individual in the PAL category of the forum ... maybe the problem is similar?

It is difficult for me to comment on your experiences, since the performance of the Zeiss Individual lens in the general marketplace has been very different. In fact, a randomized, double-blind wearer trial was recently conducted at the Clinical Research Center at UC Berkeley's School of Optometry comparing Zeiss Individual to standard progressive lenses among 95 progressive lens wearers. Although all wearers expressed a high level of satisfaction with Zeiss Individual, hyperopes actually rated the lens higher than myopes.

If someone can prod Darryl Meister from Zeiss to take a look at this thread he should be able to shed some insight as well

We generally recommend using the suggested base curve, unless there is a truly compelling reason to substitute base curves, such as the use of an 8.00 Base wrap frame. Because the Zeiss Individual lens design is optically optimized based upon the specific prescription of the wearer, the intended optical performance will generally be achieved regardless of the prescription power or base curve, within reason at least.

Best regards,
Darryl

[musicvirtuoso]

It is difficult for me to comment on your experiences, since the performance of the Zeiss Individual lens in the general marketplace has been very different. In fact, a randomized, double-blind wearer trial was recently conducted at the Clinical Research Center at UC Berkeley's School of Optometry comparing Zeiss Individual to standard progressive lenses among 95 progressive lens wearers. Although all wearers expressed a high level of satisfaction with Zeiss Individual, hyperopes actually rated the lens higher than myopes.


We generally recommend using the suggested base curve, unless there is a truly compelling reason to substitute base curves, such as the use of an 8.00 Base wrap frame. Because the Zeiss Individual lens design is optically optimized based upon the specific prescription of the wearer, the intended optical performance will generally be achieved regardless of the prescription power or base curve, within reason at least.

Best regards,
Darryl

Reviving this thread for a bit to ask you something Darryl. I definitely believe you about the study, but is there, perhaps, a factor I'm not considering? Maybe we're observing satisfaction as compared to the Gradal or GT2 (which most of them were wearing before - don't really know the percentage of each right now); would the design concepts of either of these lenses offer something to hyperopes that they wouldn't get in the Individual? Whenever I try to get more (technical) information about the Individual from our lab, they just send us some crappy consumer-oriented marketing pamphlet, so it's difficult to truly understand what's going on. Are there certain things we should be considering when fitting the Individual for hyperopes rather than myopes? Sorry to bombard you with questions, I was just curious. It's been well over a year since we started dispensing this lens and still haven't seen a change - at least 75% of the hyperopes that we fit experienced problems (so we have stopped fitting hyperopes with this lens). If what you say is the case, there obviously must be error on our part... help.... please...

[Darryl Meister]

I definitely believe you about the study

You don't have to believe me, you just have to believe the clinical research investigators at UC Berkeley's School of Optometry. ;)

would the design concepts of either of these lenses offer something to hyperopes that they wouldn't get in the Individual?

Not really. The Zeiss Individual base lens design is very similar to both Gradal Top and GT2 by Zeiss; they are all essentially from the same "family" of lens designs. Zeiss Individual simply preserves the intended optical performance of lenses like GT2 for every wearer, regardless of his or her specific prescription requirements, position of wear, or frame size.

You do not need to consider anything "special" for any prescription range. These progressive lenses were designed to offer the same optical performance to both hyperopes and myopes. Other than subtle modifications to the degree of asphericity, inset of the near zone, etcetera, there are no significant differences between the lens designs for plus prescriptions compared to the lens designs for minus prescriptions.

curious. It's been well over a year since we started dispensing this lens and still haven't seen a change - at least 75% of the hyperopes that we fit experienced problems

If you are running a 75% rate of dissatisfaction in plus prescriptions, I would say that something certainly is amiss. Our labs are currently running a non-adapt rate of less than 1% for Zeiss Individual across our US lab network. This is less than half of the non-adapt rate for semi-finished GT2 lenses. And, unfortunately, you're probably not going to resolve your issue in an Internet forum; I would strongly encourage you to contact your local Carl Zeiss Vision representative.

Whenever I try to get more (technical) information about the Individual from our lab,

Carl Zeiss Vision makes a great deal of technical information available for all of our products. You can download the Zeiss Individual white paper, if you'd like additional technical details, at PersonalizedLens.com - Zeiss Individual White Paper. While you're at it, you can also download a summary published in Review of Optometry magazine of the Zeiss Individual Wearer Trial Results.

Best regards,
Darryl

[musicvirtuoso]

Thanks for the resources, Darryl! Our rep has been kind of a brick wall. Whenever we have questions, it's met with, "It shouldn't be that way" and no return phone calls. This is why we asked them for more technical information about the Individual. That's when they sent us (twice) those commercial advertisements for it. It's a little frustrating, which is why I came here with the question. We just haven't gotten any where with our rep.

[Darryl Meister]

In all fairness, the issue that you have presented, with 75% of your hyperopics patients expressing dissatisfaction with the lens, undoubtedly defies the experience of the vast majority of our representatives with the product. Since Zeiss Individual has maintained an extremely low non-adapt rate nationally, outperformed traditional lenses in an independently conducted clinical study, and done quite well overall in the marketplace, your own experience with the product may have left your representative somewhat mystified.

Nevertheless, I am surprised to hear that he or she did not follow up with you regarding this subject in a timely manner. That is uncharacteristic of our representatives. If you continue seeing a high rate of dissatisfaction with Zeiss Individual on these wearers, please feel free to e-mail me directly, and I will try to put someone from your CZV free-form laboratory in touch with you regarding the issue. I'm sure that we can investigate and then resolve any potential causes to your satisfaction.

Best regards,
Darryl