PAL designs and intended POW

[drk]

Went to a Shamir workshop yesterday and learned something new.

"As-Worn-Quadro" available on their Autograph III is about as stupid a name as can be, but there's apparently a good reason for it.

The gist of it, as I understood it, is that a given PAL design has its limits. For example, take the Comfort2. If you tilted the lens on the X and Y axis too much, you'd get:
a. power error (which by now we all should know about)
b. "other bad stuff", which I am going to suppose is general narrowing of clear areas of vision


This is rather new to me. I knew that tilting PALs was a problem, but I have believed that power compensation would solve all of it. Apparently not so.

Shamir is claiming with their "As-Worn-Quadro" that they have four PAL designs that are presumed to be worn in four types of situations, pretty much regarding wrap:
Flat
Normal
Somewhat wrappy
Very wrappy

(Remember that they have their own sunwear designs, too. For all I know this "As-Worn-Quadro" bleeds into their sun designs.)

Question 1: What I'm "wrapping my head around" is the concept of different designs for different wrap angles. What do you think they are doing there?
Question 2: What if you take another PAL design, and do the "wrap compensation" for power thingy (say you want to use a Comfort2 with wrap compensation). Does this concept mean that you are not getting as good of wrapped vision with a design that is made for typical ophthalmic frames, than you would if you chose another PAL design that is intended to be wrapped in the first place?
Question 3: Are there other PAL designs made specifically for wrapping?

Thanks!

[Hayde]

1) I'll leave to more informed minds to answer rather than conjecture.
2) Yes, which I've proven to myself the hard way. You can break even a premier general-use PAL with enough wrap.
3) There are. Sorry I'm not recalling names at the moment, but aside from Shamir Attitudes (and didn't Varilux have one, too?)--most of the ones I've encountered were 'house' PALs by labs contracted with sunglass vendors like Liberty, Serengeti, etc. I'm sure Oakley & MJ have their own through their respective labs.

[Pete Hanlin]

Regarding "Position of Wear," there's an analogy that helps explain the need/limitations (at least it helps me understand them).

Consider a projector. If we were manufacturing projectors, and knew that our projectors would always be positioned 12' away from the screen and 8" below the center of the screen, we could "lock in" the optics to provide the best possible image on the screen- perfectly square and in focus.
Unfortunately, in real life our projectors are sometimes going to be mounted in other locations- closer or farther to the screen, higher or lower relative to the screen center, and sometimes (groan) even off to the side of the screen. If we do not build in some sort of adjustment mechanism, the optics of our projector will be compromised when the projector isn't mounted in a position we consider to be "normal." Specifically, the image will be out of focus and/or skewed/distorted. This is why nearly all projectors have the ability to change focus and adjust for skew distortion.

The same thing happens with a progressive lens. The manufacturer bases the design on an assumption of where the lens will be in front of the eye (let's say 12mm vertex, 8 degrees of panto, 7 degrees of wrap). As long as the final position of the lens is approximately in that position, the design will perform optimally. However, if the lens position is dramatically different (e.g., pantoscopic tilt and/or wrap is zero), the image produced on the retina by the lens will be negatively impacted.
Enter POW measurements. If the lens cannot be put in a "normal" position, the optician can indicate the actual position to the designer, and the designer can adjust the optics to restore optimal performance.

A couple notes:
1. If the lens is fit "normally," adjusting for position of wear provides minimal/no benefit (after all, the lens is pretty much exactly where the designer assumed it would be). Wrap frames represent an instance where the lenses are NOT in a normal position- so yes, optimal performance will require some adjustment to the optics. In most cases, dress eyewear can/should be adjusted to what approximates a "normal" fit, however.
2. POW customization does not improve the performance of the design beyond the performance it can provide when fit according to the designer's assumptions. POW customization simply restores optical performance lost to odd lens positioning.

[Quince]

Q3: From a surfacing standpoint, these specially designed wrap lenses are available to leave greater cut out. They are decentered too fit bigger frames, narrow PDs, or a combination of both.

Younger Image and Vision Ease Novel are both available as such.

Not sure how this is compared to free-form designs that can be front and backside surfaced though.

[Quince]

3) There are. Sorry I'm not recalling names at the moment, but aside from Shamir Attitudes (and didn't Varilux have one, too?)--most of the ones I've encountered were 'house' PALs by labs contracted with sunglass vendors like Liberty, Serengeti, etc. I'm sure Oakley & MJ have their own through their respective labs.

I'm like 90% sure MJs are Attitudes and maaaaaybe Oakleys as well.

[drk]

Enter POW measurements. If the lens cannot be put in a "normal" position, the optician can indicate the actual position to the designer, and the designer can adjust the optics to restore optimal performance.

Good post, but please clarify.

By "lens designer" are you referring to simply having the computer supply compensated powers? Or do you mean that actual people have pre-designed a different lens style to maximize performance for high wrap? These are the two different things to which I was referring above.

Thanks.

[drk]

I'm like 90% sure MJs are Attitudes and maaaaaybe Oakleys as well.

My impression from the Shamir guys last night was similar, regarding MJ, at least in the past (Auto II).

[Pete Hanlin]

Good post, but please clarify.

By "lens designer" are you referring to simply having the computer supply compensated powers? Or do you mean that the actual people have designed different lens styles to account for high wrap? These are the two different things to which I was referring above.

Thanks.

Progressive design is really not tied to wrap. The calculations required to make a design function optimally in a wrap application are defined by physics. You determine what image you want to place on the retina, design to it, and from that point on a calculation program is going to be able to produce that image on the retina regardless of lens positioning. Flexibility and robustness of the calculation program are the important considerations when trying to deliver a wrap lens.

Now, it is possible there may be some identified design feature that is ideal for the activities conducted while wearing a wrap frame. For example, there may be a particular distribution of distance, intermediate, and near that seems to be preferred for outside activities (actually, there is). So you could create a design with this in mind and then use the aforementioned calculations to render that design for a wrap application.

Main thing is you figure out what you want the retina to see (the design) and then you use calculations to preserve that design against exotic lens placement (wrap). A design may be created specifically to work well with a particular calculation process- but it's all just optics.

[drk]

I may be misunderstanding what I heard yesterday, but you seem to be taking another position from what I think I heard.

Let me agree with your good point here:

Now, it is possible there may be some identified design feature that is ideal for the activities conducted while wearing a wrap frame. For example, there may be a particular distribution of distance, intermediate, and near that seems to be preferred for outside activities (actually, there is).

If you are wearing a wrap frame, you're probably wearing sunglasses, and you're probably going to need more distance and less near. So, a company could make an intended design like that, and know that it's going to be wrapped (or not).

But let's leave the (achingly practical) aspect of sunwear out of it. What if you wanted to look all goofy and wear a 20 degree wrap frame with clear lenses as your ophthalmic frame? And you want everyday, balanced PAL function. Do you think you could wrap a given design (say, one of the Physio family) and get approximately the same performance as in a 7 degree ophthalmic? At least close?

Or, could an evil genius design a totally different wrap-intended design that would work better than the compensated Physio?

[Pete Hanlin]

Disclaimer- Essilor employee.

Again, I would say the design aspect is totally separate from the wrap calculation. Whatever you feel the best design is at 7 degree wrap (be it Zeiss Individual, Hoyalux iD, Varilux whatever), if you perform the correct calculations you should be able to provide the same performance at 20 degrees of wrap. If the evil genius is coming up with a design that provides better performance at 20 degrees of wrap, the reverse should be true (i.e., with the correct calculations it should be able to provide superior performance at 7 degrees of wrap)

When it comes to wrap, its a matter of pure optical calculation. The end result is going to be based on the ideal retinal image that design is capable of producing.

PS- BTW, we do have a product called Varilux Stylistic that is specifically designed for wrap applications (meaning it is designed to work with the calculations necessary to create the targeted performance of the design in a high-wrap application).

[Quince]

My impression from the Shamir guys last night was similar, regarding MJ, at least in the past (Auto II).

Them Shamir guys don't like to confirm or deny anything, though they sure like hinting

[drk]

Hey, Pete.

You seem to be affirming what I believed to be true. There is no specific "design feature" needed for a high wrap frame...just the correct powers.

But then again, Shamir has this "quadro" thing, and now you mention the "Stylistic". What, then, is the point of these lens features/designs? The "Stylistic", being a wrapper, is designed for sunglasses...i.e. good distance, lesser near?

[Pete Hanlin]

Actually, it mostly comes down to being compatible with the calculations required to support significant wrap. Plus, there are other logistical considerations when creating a "wrapper" products (blank characteristics- size, thickness, etc.). Finally, there are some design aspects that are incorporated based on the usual use of lenses going into a wrap frame (as you mentioned, they are usually used in sunwear- and considering driving is a very important activity for adult sunglass wearers...).

[drk]

What's actually kind of perverse is that we seem to be simply talking about programming a computer to accept higher variables.

And that turns into a lens brand...

...and then the marketing department gets ahold of it, and touts it as some new and improved lens...for a higher price...

...when all it is:

Old lens:
<input: wrap angle>
<values allowed 0-15>

New lens:
<input: wrap angle>
<values allowed 16-30>

[Hayde]

What's actually kind of perverse is that we seem to be simply talking about programming a computer to accept higher variables.

And that turns into a lens brand...

...and then the marketing department gets ahold of it, and touts it as some new and improved lens...for a higher price...

...when all it is:

Old lens:
<input: wrap angle>
<values allowed 0-15>

New lens:
<input: wrap angle>
<values allowed 16-30>

In their defense, the complexity of optical distortions at 16-30 is logrythmically higher than 0-15. So is the ingenuity required to address them. imo, they're entitled to some branded pride if they're getting good results to pin on it.

[drk]

Sure, they're entitled.

Here's what I think, though:

MAKE THREE LENSES!

A. Varilux (best. Incorporates everything and can be used for anything.)
B. Ovation (better. Is a fixed digital design, entry price level.)
C. Natural (good). Is a traditional grinder.

(or something).

And then make it "free upgrades" every time you re-jigger the programs, like "Windows Update".

[Quince]

Sure, they're entitled.

Here's what I think, though:

MAKE THREE LENSES!

A. Varilux (best. Incorporates everything and can be used for anything.)
B. Ovation (better. Is a fixed digital design, entry price level.)
C. Natural (good). Is a traditional grinder.

(or something).

And then make it "free upgrades" every time you re-jigger the programs, like "Windows Update".

Even if companies want to rename it- phase the old one out. Enter Varilux X, exit Varilux S. Why you need to have both, I couldn't imagine. This adds simplicity. Everytime Transistions lenses are revamped they don't get renamed- why should lens styles?

Like Tallboy mentioned- it should have been called 'El Ocho.'




Whoops! Totally just mixed up two threads... well this still applies!

[PartTimer]

In their defense, the complexity of optical distortions at 16-30 is logrythmically higher than 0-15. So is the ingenuity required to address them. imo, they're entitled to some branded pride if they're getting good results to pin on it.

Absolutely right. I know lots of ODs that are utterly convinced by this sort of marketing, so I certainly don't blame Varilux. We are all in this for business to some extent, and we all do marketing and branding in our opticals.

That being said, that also doesn't mean I can't make fun of it. It's all I have, sometimes, and it's one of the few things I'm better at than most people.

I do want to add that Pete seems to have a thick skin, and I always appreciate his input. Even when the topics don't turn to Varilux, he usually has great input, and of course his personal perspective there is useful to us all.

[merrymaker]

Great thread and much appreciated input from Pete.

[Speed]

Not too sure about POW compensation. Rodenstock had a simi-finished progressive "compensated for POW" a few years ago. I am not convinced that making an add weaker works for POW. Seems that for more panto the add would need to be stronger.