Digital surfacing. (There, I said it.)

This is the only place in the world to discuss this.

Ok, so I have been told by someone who should know (wholesale lab rep) that digital surfacing is better than traditional surfacing.

I saw some pictures of the process, and it looks like "a needle" cuts a rotating lens.

Why is digital surfacing better? Because complicated surfaces can be cut that minimize abberation (I believe). The back surface of a digitally surfaced spherocyl may not be the "inside of a teaspoon" shape, but something that resembles a landscape with rolling hills (very, very, rough, there).

Why is digital surfacing better? This may be something I imagine I heard, but, similar to how progressives are designed with ray-tracing to correct the off-axis powers at different angles of gaze, this technology can be applied to the design of higher power SV lenses, as well. Does anyone know if I'm even close on that one?

Why is digital surfacing better? Whether digitally surfacing a mold for the front surface of a progressive, or surfacing an actual lens, the process itself is "cleaner and more precise".

The question is: how much better, and who will perceive it? We may be in a transitional state where we need to identify who will benefit from these incremental improvements, until it becomes commonplace.

This is just opinion, but I think just the digitally surfaced part doesn't amount to a hill of beans. The true improvements come in the design of the lens. If the lens is digitally surfaced to a spherical shape than you just took the long way home thats all. If the lens surface is freeform and this change in form is optimized to rid certain aberations than you have something and I think even in this case, the people that are going to truly notice is the ones with higher cyl's, higher powers, and oblique axis's.

I think that's a pretty good point: that the main advantage of digital surfacing technology is the ability to "do more" with lens design.

Anyone heard about the "abberation controlled SV lens" concept?

I have heard of the i-zon I think it is called that is supposed to eliminate or reduce aberation, I haven't actually seen the lens or even heard any feedback about it. I understand the concepts and how they work, but like you said I would love some feedback as to if the lenses make a difference. It should slowly unfold in the near future as everone seems to be rushing to have a free form lens.

drk said:

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Why is digital surfacing better? Whether digitally surfacing a mold for the front surface of a progressive, or surfacing an actual lens, the process itself is "cleaner and more precise".

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The above statement is correct however both glass and metal molds have been made by digital surfacing for years. The lens manufactures are using this term to imply new precision lens production. In many cases these lenses are produced the same way as the previous lenses produced.

Harry said:

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The true improvements come in the design of the lens.

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This is the benefit to digital surfacing.

I do not have the space here to explain all of the advantages to digital surfacing lens designs.

I will site one example: A plus PAL lens, with the PAL design cast on the front of the lens that requires a 2 base back curve will have an edge thickness for a 50mm A dimension that is quite thick. This edge thickness can not be smaller because the front design must work for all A and ED measurements even a 60mm or more. An individual digitally surfaced plus lens of the same power can have most of the abberations removed with a complex design. This design can be made for the smaller 50mm A measurement frame and a big percentage of lens weight can be eliminated by this digital surfacing in addition to wider usable lens area.

Keep in mind that "Digital surfacing" isn't a process; it is just one particular manufacturer's "branding" of a relatively common process.

All modern generators are "digitally" (CNC) controlled, and many use a single-point turning process. The main advantage to the use of a "free-form" generator is the ability to produce complex surfaces with a high degree of accuracy and smoothness. This is important because hard lap fining and polishing cannot be used on complex surfaces, and soft lap polishing can distort the shape of the surface with extended polishing (this effect is dependent on the shape of the part).

However, as Harry and Allen pointed out though, this doesn't really offer the final wearer any meaningful benefit over a traditionally surfaced lens unless the process has been used to create a unique, individualized lens design based on factors specific to the wearer (including modifications to the design based on the prescription, fitting measurements, and so on). If you use a free-form generator to produce a basic toric -- or even progressive -- lens design, you really aren't achieving anything that a traditional lens couldn't deliver.

Further, while free-form generators arguably replicate a lens design more accurately than casting (which I would consider a relatively robust and repeatable process), the free-form process must be very carefully engineered to ensure that the final product maintains good form accuracy after soft/flex polishing. Just because the lens looks good off the free-form generator, doesn't mean that it will look good at the end of the process.

Darryl offer a great explaination regarding digital surfacing and freeform products and processes.

As Darryl pointed out there is a great deal of technical experience required to complete the non-spherical surface.

There are three basic techniques used for lens production:

1- Finished lenses ready to edge
2- Traditional spherical backside surfacing with hard laps, pads and polish used to finish the lens
3- New individualized freeform-digitally surfaced or what ever new buzz word is adopted lenses produced without traditional hard laps. (To maximize this type of lens production they must be combined with a sophisticated lens design.)

Thanks for the knowledgeable responses.

So, to summarize:

--"Digital surfacing" of molds or lenses is not "new" or necessarily better.
--All advantages that may occur with such capability is primarily due to ability to design better lenses.


I think we're all now familiar with the concept of individualized, back surface-utilizing progressive designs.

Then, what about a digitally surfaced SV lens for less off-axis aberration? Is this a unique ability of digital surfacing? Can we assume that the molded front surface aspheric SVs could be further enhanced to near non-aspheric optics, or even better than non-aspheric optics? Could ray-tracing and complex back surface curves give us better SV lenses?

Drk, that is actually where AWTECH's company shines. The SV lenses can be enhances with ditital processing and improved designs. Especially when thickness is a concern.

Forgive my persistence, but what is the gist of that?

Can you:
1.) Flatten plus lenses with higher eccentricity aspheric lenses on the front, but add "special" curves on the back to offset any decrease in aberrations that are induced by the "excess" eccentricity on the front?

2.) Steepen minus lenses in the periphery above and beyond the norm, and offset the induced aberration on the backside?

drk said:

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I think we're all now familiar with the concept of individualized, back surface-utilizing progressive designs.

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I think this maybe over simplified. I can tell you from personal experience that those of us who work with these new technologies are constantly amazed at what we either are accomplishing that we did not realize or can accomplish with time, effort and a little $

drk said:

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Then, what about a digitally surfaced SV lens for less off-axis aberration? Is this a unique ability of digital surfacing? Can we assume that the molded front surface aspheric SVs could be further enhanced to near non-aspheric optics, or even better than non-aspheric optics? Could ray-tracing and complex back surface curves give us better SV lenses?

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You are on the right track with this thought. My only correction is you seem to have assigned as the lens industry has some hidden meaning to aspheric. Aspheric means one thing non-spheical and if you go to non-aspheric optics you would be back where we started with spherical lenses.

We specialize in backside aspherical designs both single vision and progressives. We started with keeping the front spherical for one main reason and that is our background was in polarized lenses. To keep the polarized lenses at maximum performace the polarized film must be as close to the front of the lens as possible. With a spherical front curve we can accomplish this. We then began working with the leading individual PAL lens design company and adapted what they have been doing for over 10 years to our technologies to offer the products that we currently have.

Trying to understand all of the dynamics is a brain twister. Don't get a headache over this just absorb it slowly and use these new products. Your patients will really appreciate you introducing them to better vision. Which is the goal.

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Originally Posted by drk

Forgive my persistence, but what is the gist of that?

Can you:
1.) Flatten plus lenses with higher eccentricity aspheric lenses on the front, but add "special" curves on the back to offset any decrease in aberrations that are induced by the "excess" eccentricity on the front?

2.) Steepen minus lenses in the periphery above and beyond the norm, and offset the induced aberration on the backside?

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I haven't actually designed any of these lenses or computed the figuires to know if it is feasable to ofset aberations by using a different asphericity on the back, but would assume that it would be possible. The thickness thing I was talking about is that AWTECH's company actually makes the polarized suns where they determine an optic zone and then use the lens periphery to thin them out. I have heard they look really nice and am still waiting for a picture (hint hint).

Thank you, both.

Ok, then, can I say this:
We will be moving into an era of increased cosmetic appearance of high Rx SV lenses, to go along with our era of increased progressive lens performance? Are we going to have better "off axis" vision above and beyond the "corrected curve" historical standard?

drk: I think the ball is now in your court so to speak. The refraction side needs more accuracy and consistency for the lenses produced to be more accurate. As an OD recently told me. You can go to five different OD's and get 5 different prescriptions. Yet when it comes to lenses the any O's want it exactly the same.

Well, that's a good point.

There is always a concern that we have "over-improved" our house because the neighborhood's not that good.

In other words, all this ophthalmic lens design refinement is great, but it's only one link in a chain of events--clear ocular media, moderate to high visually sensitive patients, consistent refraction procedures may well be the limiting factors in the process.

We have to understand this new technology well enough to know whether applying it will give anything close to the desired results! It may be a waste, especially in the emerging, more expensive phase of this move forward.

drk said:

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We have to understand this new technology well enough to know whether applying it will give anything close to the desired results! It may be a waste, especially in the emerging, more expensive phase of this move forward.

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To help you understand the some of the advantages, (I will try not to make this a sales pitch), the benefits I will focus on lens designs that I am very familiar with. Having worked very close with Seiko Epson the technology partner behind Seiko lens designs I can tell you that the benefits to their approach will work very well with all current information needed such as OC height, PD, A, B, ED, sphere, cylinder, axis etc. This allows for the individualized lens being produced with between 20% to 30% more usable area. With more usable lens area there is also greater room for fitting errors. These types of designs will become more and more popular since fitting errors will not require as many remakes because the patient can still use the progressive from top to bottom and from side to side. A good case can be made to use this type of lens and make sure your least experienced opticans fit only this lens, less mistakes, fewer remakes, more happy patients.

The ICE-TECH Advanced Polarized sunlens is a fantastic lens 8 base front curve and -6.00 sphere fully compensated with a lens carrier area on the temple side. Large optical zone minimum of 50mm and usually 55mm or more. All that is needed to fit this lens to a wrap frame, is the frame, and the OC height, any change in vertex distance, and the patient Rx with PD.
This is a product that only ICE-TECH offers and patients with strong Rx's have been asking for.