I have a wrap compensation problem...

[Barry Santini]

Hi Harry...

You are correct...it is not just spherical aberration and marginal astigmatism, it is off center errors, and others. Thanks for briging that up.

The Attitude design also deals with those errors, I did not mention them specifically.

My point: you shouldn't have to do additional compensation when the design considers the variables and counter-acts them in the mold itself.

Instead of compensating, I would simply start with a design optimized for wrap, like the Attitude (available in SV and PAL).Laurie

Laurie, in this case, I disagree...
My understanding is that *central* acuity has to be compensated for the lens/wrap/panto and VD changes from nominal refractive findings (flat lenses; Zero Pantoscopic tilt) in order to try to mimic the acuity found in the exam room.

One point, left out so far from this discussion, is the meridonal/peripheral magnification changes that influence the neurological perception of the wearer. The "fishbowl" effect of wearing wrap eyewear would be one example.

FWIW

Barry

[Laurie]

Hi Barry,

Fish bowl and other optical problems will occur when the base curve is way off. It is primarily about best form lens design.

If, for example, you input variables in a lens design program (like Darryl Meister's 'Optics Lite',) and you plugged in the correct base curve (using Thompson's equation), you would find that a steep wrap induces too much spherical aberration, and off-center errors.

The best way to deal with these errors optically is to induce equal and opposite errors in the mold, so that light neutralizes the effects when passing through.

Even with a wrap compensating calculator, you cannot acheive the same results as you would with a lens specifically designed for these errors, like the Attitude design. With a wrap-compensating formula, you can adjust some parameters, however, a design optimized for this purpose encompasses many more variables...up to 300 curves on one surface.

In this case, I would trust the lens designers, who use super-computers to calculate and finalize the end-design...if in fact, the design is actually optimized for high base curves, rather than 'just being available' in steeper base curves.

Vertex Distance should not be an issue, unless the power is greater than +/- 7.00 D in power...it is the base curve issue, straying away from the best form designs that is the major factor.

: )

Laurie

[AWTECH]

Hi Barry,

Fish bowl and other optical problems will occur when the base curve is way off. It is primarily about best form lens design.

If, for example, you input variables in a lens design program (like Darryl Meister's 'Optics Lite',) and you plugged in the correct base curve (using Thompson's equation), you would find that a steep wrap induces too much spherical aberration, and off-center errors.

The best way to deal with these errors optically is to induce equal and opposite errors in the mold, so that light neutralizes the effects when passing through.

Even with a wrap compensating calculator, you cannot acheive the same results as you would with a lens specifically designed for these errors, like the Attitude design. With a wrap-compensating formula, you can adjust some parameters, however, a design optimized for this purpose encompasses many more variables...up to 300 curves on one surface.

In this case, I would trust the lens designers, who use super-computers to calculate and finalize the end-design...if in fact, the design is actually optimized for high base curves, rather than 'just being available' in steeper base curves.

Vertex Distance should not be an issue, unless the power is greater than +/- 7.00 D in power...it is the base curve issue, straying away from the best form designs that is the major factor.

: )

Laurie

When you deal with the errors you mention by correcting for errors in the mold you have limitations due to various differences in frame angles when the lens is designed to be optimized at a specific angle. With an individualized wrap around design using both compensation and the optimized lens surface design based on the frame and patient information you will get an even better lens.

The main advantage the Attitude has over the individualized lens is that it can be processed with standard lab surfacing equipment.

[Barry Santini]

Laurie,

As I have discovered in telescope-eyepiece design:

If you optimally correct off-axis errors, such as astigmatism and the mis-match of image planes {sometimes incorrectly referred to (at least in telescope design) as "field-curvature"}, you will end up with meridonal magnification errors (aka rectilinear-geometric magnification errors). This is the situation, similar to optimized wrap-ophthalmic errors, that results in the wearer's perception of a "fish-bowl" effect with wrap eyewear.

Some people may not "notice" it, but its there nevertheless.

FWIW

Barry

[HarryChiling]

Barry,

Your right their is no real great way of produceing an orthoscopic lens in a wrap design. If we go off corrected curve I think that distortion is going to be the least of our worries when it comes to aberrations. Using conventional base cure their is no way to get rid of distortion anyway so it's not often a concern. To minimize the distortion you talk about we would need to go into the Wollaston branch of the tchernings ellipse. The wollaston curves are too steep for wraps or any ohter lens to be a viable option so we can't really take that into consideration fro correction, but we do need to take that into consideration as a contraindication. If we haev a patient that is sensitive to base curves then this is going to be the patietn that has issues with distortion.

Even with a wrap compensating calculator, you cannot acheive the same results as you would with a lens specifically designed for these errors, like the Attitude design. With a wrap-compensating formula, you can adjust some parameters, however, a design optimized for this purpose encompasses many more variables...up to 300 curves on one surface.

I am not sure what association you have with Shamir, I agree their products are great, but any molded lens is going to provide some comprimise in design to give it a wider range of prescriptions to accomadate. Of course shamir coudl make a billion molds to eliminate this issue, but then they could also go with FF processing of the lens instead and save a boat load of money. I think before seidel aberrations shoudl be addressed the first order aberrations shoudl be compensated for first, defocus and astigmatism, to say we need to focus on the higher order aberrations and leave defocus and astigmatism unaddressed would be like plugging a hole in a damn with bubble gum.

[Barry Santini]

Using conventional base cure their is no way to get rid of distortion anyway so it's not often a concern. To minimize the distortion you talk about we would need to go into the Wollaston branch of the tchernings ellipse. The wollaston curves are too steep for wraps or any ohter lens to be a viable option so we can't really take that into consideration for correction, .

Harry,

I'm sensing from this post that you may not have been aware, or used any of Sola Enigma/Contour Optics lenses/eyewear. I have and still use 4 pair of them (2 pairs for music, 1 DV for night driving and 1 Sunglass).

My friend, and Sola/Zeiss lens designer, Mike Morris (who is also an avid amateur astronomer), designed these same lenses by goin' back and lookin at the Wolllaston branch of steep curves. He settled on the idea that a curved lens of 16Diopter, placed approximately 16-18mm VD, would then have a "base curve" whose radius is co-incident with the center of rotation of the eye. Therefore, the eye's line of sight is "normal" just about everywhere one looks...even very obliquely. His idea came from trying to design an ophthalmic lens that mimics the Maksutov telescope design (if you have to ask, Wiki it)

No distortion, no astigmatism, no power error and...NO Color aberration, even though the lenses were Poly (which made molding them possible).

I'm so sorry to see Zeiss compleetly throw out this technology when they bought Sola.

FWIW

Barry

[HarryChiling]

Harry,

I'm sensing from this post that you may not have been aware, or used any of Sola Enigma/Contour Optics lenses/eyewear. I have and still use 4 pair of them (2 pairs for music, 1 DV for night driving and 1 Sunglass).

My friend, and Sola/Zeiss lens designer, Mike Morris (who is also an avid amateur astronomer), designed these same lenses by goin' back and lookin at the Wolllaston branch of steep curves. He settled on the idea that a curved lens of 16Diopter, placed approximately 16-18mm VD, would then have a "base curve" whose radius is co-incident with the center of rotation of the eye. Therefore, the eye's line of sight is "normal" just about everywhere one looks...even very obliquely. His idea came from trying to design an ophthalmic lens that mimics the Maksutov telescope design (if you have to ask, Wiki it)

No distortion, no astigmatism, no power error and...NO Color aberration, even though the lenses were Poly (which made molding them possible).

I'm so sorry to see Zeiss compleetly throw out this technology when they bought Sola.

FWIW

Barry

That is the idea behind the wollaston branch and I love hearing even from instructors that their is no way of correcting chromatism without a doublet or triplet. Yes, a steep enough curve will correct it, but even the design you suggest which I am not familiar with is a bit outrageous when it comes to feasability especially in a wrap. Maybe you could reintroduce them as Super Wraps^TM. :D

If you were to push the VD even further out you could make the lenses in a more acceptable base curve but how realistic would it be. Two characteristics of wrap eyewear make this design a flop:

1. Base Curve - most wrap eyewear are suited for 6 - 10 base lenses at best, outside of this range steep adjustments nee to be made to the curves to make them fit properly.
2. Vertex Distance - in the design you specified the VD was moved to a 16 - 18 mm distance where as in wraps we deal with the opposite with VD 8 - 10 mm on average.

If I am correct most of the Tcherning charts I have seen measure the back vertex to center of rotation as 25 - 27mm consider about 12.5 from cornea to center of rotation and that leaves us with 12.5 - 14.5mm for the vertex distance in these charts which would even be slightly off for our 8 - 10mm vertex distance. If I get a chance I might try to draw up a chart for closer vertex's.

[Barry Santini]

Harry,

these lenses were designed to be worn in a NON wrap frame, i.e. "0" frame tilt. The lenses are simply very steeply curved to perform as I mentioned.

When I come to VEE, I'll bring mine, if you're interested.

Barry

[HarryChiling]

Harry,

these lenses were designed to be worn in a NON wrap frame, i.e. "0" frame tilt. The lenses are simply very steeply curved to perform as I mentioned.

When I come to VEE, I'll bring mine, if you're interested.

Barry

I understand, but the effect or orthoscopy that these lense porduce cannot be produced at a closer VD frame (ie wrap sunglasses) without even steeper curves beign employed. They are in effect made usign the wollaston curves from the tcshernings ellipse except they have the vertex distance moved further out to allow for flatter wollaston curves.

BTW, I will be their on Saturday so I would love to see them.

[Laurie]

Hi Harry,

My association with Shamir is as an educational consultant. I teach optics full time at Hillsborough Community College, and do consulting and writing in addition to my faculty position.

I wholeheartedly agree, that freeform is the way to go in all lenses. It is an amazing technology.

What I was trying to point out, though, IMHO, is that it is better to choose a lens that is optimized for wrap, rather than take a spherical base and run the numbers through a compensating program. The best of the best, of course, is comining all of these technologies together for a truly personalized lens.

...baby steps.

: )

Laurie

[snowmonster]

My association with Shamir is as an educational consultant. I teach optics full time at Hillsborough Community College, and do consulting and writing in addition to my faculty position.

Laurie

Call me crazy, but shouldn't this have been disclosed much earlier in the conversation?

At least we know what Allen's background/motivation is in all of his posts.

[Laurie]

Hi Snowmonster,

I talk about lots of products/technologies here, Nupolar, Transitions, Chrome Hearts, ect. I have mentioned my affiliation with Shamir here more than once in the past...sorry if you didn't catch it.

no intentions to hide anything!

: )

Laurie

PS: Barry S., if you are reading this, how about a prototype that you can show us at Expo?

[HarryChiling]

I wholeheartedly agree, that freeform is the way to go in all lenses. It is an amazing technology.

I don't think I ever said that, matter of fact I believe that in many prescriptions the benefits of the processing technique will never be fully appreciated. The more comprimised the Rx is from corrected curve the more likely the patient is to realize the benefits of FF processing to reduce that comprimise, however if your Rx happens to fall on the corrected curve that the manufacturer just so happens to also make blanks in, then FF or not a spherical back curve would accomplish the same on both the FF generator or the traditional generator. It could even be argued that the conformable polishers would introduce more error in these cases than the spherical hard laps. It's a great technology and one day enough people will understand it enough to only fit it in cases that would benefit from it's pluses.

What I was trying to point out, though, IMHO, is that it is better to choose a lens that is optimized for wrap, rather than take a spherical base and run the numbers through a compensating program. The best of the best, of course, is comining all of these technologies together for a truly personalized lens.

The best of the best is here, those lenses that are optimized for wrap still get compensated and perform better when they do. These optimized lenses that you are mentioning are optimizing aberrations which is nice but keep in mind the script from the doctor addresses defocus and astigmatism and before we can move forward to the more complicated and sexier seidel abberations we need to adress the astigmatsim and the defocus.

If I had to fit a patient in a compensated aspheric lens without any compensations through the various programs or a spherical lens with the compensations through the program hands down I would go with the spherical lens.

Call me crazy, but shouldn't this have been disclosed much earlier in the conversation?

At least we know what Allen's background/motivation is in all of his posts.

That's why I asked, I know Laurie is an educator and she may not be getting the correct information from these companies on the subject. This is common in our industry and I have always made it a point to never believe what I am told without checking the facts first.

[Laurie]

Hi Harry,

I realize best form theory is tough to beat. It is amazing how much choosing the right base curve matters.

My responses about aberrations, ect., were out of my courses, in my head...not given to me by companies. Kind of reading stuff here, and applying optical common sense, and submitting a reply.

It is pretty common for educators to do additional work with various companies...one friend of mine has 5-6 affiliations...However, we keep it out of the classroom. Everyone who knows me here knows that I seperate classroom and business. I did not realize though, as you stated, that it is common for optical instructors to get the wrong information from companies?

Usually manufacturers are great about sending us spec sheets, and we have guest speakers from all types of companies to present to our students....not sure what you mean by the commonality of mis-information.

Back to topic:

Are you suggesting that a compensated, aspheric front run through a compensating program is better than a design that compensates in the mold, and can be traditionally surfaced, or, additionally direct surfaced?

I'm just stretching it out here. It will likely take a while for all of these technlogies to become the norm, but we've lived through other big changes...it will be interesting to watch over time.

: )

Laurie

[HarryChiling]

Are you suggesting that a compensated, aspheric front run through a compensating program is better than a design that compensates in the mold, and can be traditionally surfaced, or, additionally direct surfaced?

I'm just stretching it out here. It will likely take a while for all of these technlogies to become the norm, but we've lived through other big changes...it will be interesting to watch over time.

: )

Laurie

I am not suggesting it I am saying it, Yes. If you were to take an Rx that the doctor prescribes on a specific (x,y,z) plane and then tilt the plane their will be a change in the Rx to reflect the change in this plane. If we had a phoropter that coud be tilted to the same degree's as the frame before the refraction then we would be able to apply the Rx as is to the wrapped frame, but untill then the compensations done in the mold are just done to help with the aberrations produced by prescriptions that are not corrected curve.

I think the bestt question you could ask is what does this compensation in the mold accomplish? If it's done in the mold it obviously can't be for the amount of panto or face form tilt in a specific frame. If it's done in the mold then it obviously can't be for anything patient or frame specific. What they can compensate for is a global variable that woudl be consistent across all lenses (Base Curve), very much like the Kbco lens that uses an 8 base with varying aspheric values to compensate for the various prescription ranges that will be pushed into an 8 base that don't belong there. This is the type of optimization that I believe they may be doing.

I just looked at the attitude lens and it's only available in an 8 base and supposedly covers a wide raneg of prescriptions. If you have more concrete info I would be interested in hearing about it.

[Barry Santini]

Laurie

PS: Barry S., if you are reading this, how about a prototype that you can show us at Expo?

I'll be bringin' my enigma/contours for those interested in seeing them to VEE

Barry

[Laurie]

Hi Barry,

I have a pair too...l-o-v-e them! Unfortunately, one of the drill-holes has a slight crack, can no longer wear them...love to look at them!

: )

Laurie

[drk]

Laurie:

I think it boils down to this:

1. Lens tilt compensation for sphere/cyl/axis/prism must be made. These are "first-order aberrations". Your posts seem to indicate that you don't recognize this phenomenon.

2. Compensation for all the other mind-numbing stuff is secondary. These are "higher-order aberrations", and I do think that Shamir is trying to address these.

By simply using an Attitude lens, you will get #2, but not #1, unless you compensate the lens powers using a calculator THEN order it in an Attitude lens.

Agree?

[AWTECH]

Laurie:

I think it boils down to this:

1. Lens tilt compensation for sphere/cyl/axis/prism must be made. These are "first-order aberrations". Your posts seem to indicate that you don't recognize this phenomenon.

2. Compensation for all the other mind-numbing stuff is secondary. These are "higher-order aberrations", and I do think that Shamir is trying to address these.

By simply using an Attitude lens, you will get #2, but not #1, unless you compensate the lens powers using a calculator THEN order it in an Attitude lens.

Agree?

I doubt that anyone is really trying to correct for high order abberation with a lens supported in a frame.

You can go much further with optimization than an Attitude lens. Individually designed lenses can offer better optics and be made thinner.

Our business was developed making wraps using maximum optimization.

[drk]

Maybe I am not using "higher order aberrations" correctly...defocus, yes. Spherical aberration, yes. But trefoil, coma, etc. I guess is "higher order aberrations".

I meant to say "Seidel aberrations". I guess those would be curvature of field, spherical aberration (again), transverse astigmatism, lateral marginal chromatic astimatic transverse curvature...aargh!

[Fezz]

I'm getting a headache!!


(And it's not the beer wiseguys)

[AWTECH]

Maybe I am not using "higher order aberrations" correctly...defocus, yes. Spherical aberration, yes. But trefoil, coma, etc. I guess is "higher order aberrations".

I meant to say "Seidel aberrations". I guess those would be curvature of field, spherical aberration (again), transverse astigmatism, lateral marginal chromatic astimatic transverse curvature...aargh!

Transverse astigmatism and power error are compensated for in each ICE-TECH individualized lens. The difference in a lens like the Attitude is that since this is molded lens blank the only available compensation in design must be done using spherical curves that are cut as determined by traditional lab calculation software. An ICE-TECH lens is design based on the patient prescription, the frame data and the position of wear. With this information an individually designed lens is created. If an A dimension on one frame is 62mm and on another the A=51mm then they will each have a different design, meaning the surface design, as the reading area for both will be of similar size yet they require different distance areas. Each one optimized for the specific A dimension. Across the lens surface a design is created that will maximize the performance and balance astigmatism and power error. There are just many more opportunities to maximize the design when you are not trapped with a molded PAL front surface.

[HarryChiling]

Transverse astigmatism and power error are compensated for in each ICE-TECH individualized lens. The difference in a lens like the Attitude is that since this is molded lens blank the only available compensation in design must be done using spherical curves that are cut as determined by traditional lab calculation software. An ICE-TECH lens is design based on the patient prescription, the frame data and the position of wear. With this information an individually designed lens is created. If an A dimension on one frame is 62mm and on another the A=51mm then they will each have a different design, meaning the surface design, as the reading area for both will be of similar size yet they require different distance areas. Each one optimized for the specific A dimension. Across the lens surface a design is created that will maximize the performance and balance astigmatism and power error. There are just many more opportunities to maximize the design when you are not trapped with a molded PAL front surface.

I agree that lenses can be optimized to a greatr degree using a different processing method such as FF, yet I am not convinced that labs are doing this yet to the degree you have written in your post and I would assume that you will retort with that's proprietary information.

[Barry Santini]

With this information an individually designed lens is created. If an A dimension on one frame is 62mm and on another the A=51mm then they will each have a different design.

Yes, good point. And its also important to remember that the job with the 62 E will NOT be as "potentially-optimizable"(?) as the 51E, all other things being equal.

Barry

[AWTECH]

Yes, good point. And its also important to remember that the job with the 62 E will NOT be as "potentially-optimizable"(?) as the 51E, all other things being equal.

Barry

Obviously the smaller the optical area the less off axis errors, however the 62mm lens can be optimized much better using an individualized design approach than starting with a molded blank that is designed for any frame from 46mm to 72mm.

There will continue to be improvements in the designs of individualized lenses, but the leap from molded to individualized designs is a giant step for those with vision impairment, while the next improvements will be baby steps.