# Optical Forums > Progressive Lens Discussion Forum >  What is a FreeForm?

## IC-UC

My question relates to the ability of the lens to be tailored to a frame, where you may need a bit more inset than a regular fit. We do a fair amount of polarised and tinted freeform lenses, but find them quite restrictive in lens diameters.
When an inset gets beyond, say, 6 or 7 mm, we are usually told the lens will not cut out.
My understanding of freeform (and i refer to spherical front, DS on back) is that the lens is "customised" and that inset/decentration/prism (whatever you want to call it) should/can be cut into the back of the lens?
Am I wrong in this assumption? I know that there are restrictions, but the PD's or insets I am looking for are not, IMO, too much to ask for.

Please shed some light on this for me.

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## shanbaum

Some lens design systems can produce decentered surfaces and some just don't. In any case, all of the process machines - generator, polisher, engraver - have limitations related to a decentered surface (which is not unlike a surface tilted to induce prism); the main problem is increasing travel of the cutter assembly on the generator - they can only move so far, so fast, before bad things start happening (e.g., ringing, overshoot).  Steeper curves (i.e., minus lenses) are more problematic than flatter ones.

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## sharpstick777

Also, 
1) with some 100% digital lenses some companies process all of their lenses on center for faster or simpler production.  
2) not all digital lenses are 100% digital, they use a traditional blank with a cast add and only process the distance digitally, thus they can't move the add.

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## IC-UC

> Also, 
> 1) with some 100% digital lenses some companies process all of their lenses on center for faster or simpler production. 
> 2) not all digital lenses are 100% digital, they use a traditional blank with a cast add and only process the distance digitally, thus they can't move the add.


They told me they use spherical blanks, so i would asume they would have the ability to decentre the progressive which is seemingly not the case. How do you ascertain that they have in fact used/made a freeform lens? Anyway of a quick check?

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## Mauro.Airoldi

The esy way is verify if laser marking are on front (standard cast add.) or in concave (freeform)

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## WFruit

> They told me they use spherical blanks, so i would asume they would have the ability to decentre the progressive which is seemingly not the case. How do you ascertain that they have in fact used/made a freeform lens? Anyway of a quick check?


Which brand of Free Form are you using?  We run both Seiko and Shamir.  Shamir lenses are dectentered based on frame dimensions and POW measurements (if any).  Seiko lenses use pre-marked blanks by material and cannot be decentered (well, I suppose in theory they can be, but it's something we would actually have to tweek manually).

Because we don't run them, I don't know if Zeiss or Hoya can be decentered, but given their design processes I would guess not.  Hopefully Darryl will come along and enlighten us on Zeiss at least.

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## IC-UC

> Because we don't run them, I don't know if Zeiss or Hoya can be decentered, but given their design processes I would guess not. Hopefully Darryl will come along and enlighten us on Zeiss at least.


Is this because they do dual-side digital surfacing, or because they use conventional progressive blanks and DS the back? 
The lenses we most have issues with is the Ideal. I have norticed that the Zeiss lenses do seem to come decentered, but have not really looked into the Hoya iD.

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## WFruit

> Is this because they do dual-side digital surfacing, or because they use conventional progressive blanks and DS the back? 
> The lenses we most have issues with is the Ideal. I have norticed that the Zeiss lenses do seem to come decentered, but have not really looked into the Hoya iD.


They are NOT conventional blanks with DS backs. And if I worked for either company I'd be highly offended to hear the lenses described that way. To the best of what I know, (and again, we do not processes either of these in our lab, so if I'm wrong, somebody please correct me) both the front and back surfaces are modified, based on each individual Rx and POW information. While this differes from Seiko and Shamir's processes, I would still consider them Free Form due to each lens being unique to each order.

I honestly don't mean to Essilor bash, but the only time I've heard anything postitive about the Ideal is from their marketing department.

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## IC-UC

When I say conventional blanks, I mean the front is pre-moulded (whether digitally or not) and the digital design is then surfaced onto the back. In my time at the lab, we were just setting up the "freeform" generators, and at no time was front surface generating discussed.
So if they are using pre-moulded or conventional fronts, then they can not decenter the blanks which then makes it less a freeform than one which is done on a spherical front, IMHO.
I may be way off target here with my simplification of the process, but this is as far as i know about these lenses as each company (and optom) has their own opinion on what a freeform lenses is. I guess whoever spends the most on marketing will win that battle!

But i woul like to know if all Freefrom lenses should be able to be decentered, to a certain degree, and if not do we still call the freeform or just digitally surfaced lenses?

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## WFruit

> When I say conventional blanks, I mean the front is pre-moulded (whether digitally or not) and the digital design is then surfaced onto the back. In my time at the lab, we were just setting up the "freeform" generators, and at no time was front surface generating discussed.
> So if they are using pre-moulded or conventional fronts, then they can not decenter the blanks which then makes it less a freeform than one which is done on a spherical front, IMHO.
> I may be way off target here with my simplification of the process, but this is as far as i know about these lenses as each company (and optom) has their own opinion on what a freeform lenses is. I guess whoever spends the most on marketing will win that battle!
> 
> But i woul like to know if all Freefrom lenses should be able to be decentered, to a certain degree, and if not do we still call the freeform or just digitally surfaced lenses?


Only the Essilor Enhanced (and 360, but it's being replaced by the enhanced) use conventional pre-molded front and digitally surfaced backs.

Hoya and Zeiss both use spherical blanks and then modify the front and back surfaces (I really need to message Darryl and have him explain it better, at least for the Zeiss lenses.)

I've posted this before, but I'll do so again:

Free Form = Blanks begin as a spherical front surface blank. Each lens is customized by individual Rx. Shamir and Seiko designs modify only the back surface, while Hoya and Zeiss designs modify the front and back surfaces.

Digitally Surfaced = Conventional molded blank surfaced on a Digital generator. Some lenses, such as Essilor's Enhanced designs, are also run through specific software to improve Rx accuracy.

Since decentering is a concern of yours, I would then counter with this question: If I run a decentered VIP through a Digital Generator, would you consider it to be Free Form, since it is both decentered and Digitally Surfaced? Or is it just a Digitally Surfaced VIP (never mind that digitally surfacing a VIP won't make it one bit better than conventional surfacing).

I'm going to guess reason front surface modification was not discussed in the lab that you were in is because it was neither a Zeiss nor Hoya lab. The front surface modification processes are proprietary to those two respective companies.

Specific to the Ideal, they should be able to decenter the lenses to insure cutout, unless Essilor's software is actually that bad. What they need to be doing, and it sounds like they aren't, is a Frame Centered grind for the lenses, as opposed to a blank centered grind. The solution to this could be as simple as changing what box is checked in the software.

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## Bill Mahnke

Both surfaces of HOYA's FF progressives are *Atoric*, if the Rx has cyl.

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## jcamp

Why don't they look better in the lensometer?

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## sharpstick777

> Why don't they look better in the lensometer?


jcamp,
are you refering to free-form in general, or a specific lens?  Thanks

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## HarryChiling

We've reached a point where FF, DS, HD, etc don't matter.  This month the Varilux DRx will come out and the marketing departments ability to say, "yeah we have a lens that does that and it's no better" will be here to further muddy the waters.  Is the design good?  Above in a post the VIP digitally surfaced on the back was supposedly no better, but actually it could be made better if the Rx being grinded included aspherics to improve the optics and deliver the intended design.

Delivering the intended design, the truly free form lenses have the ability to determine the intended design on the fly and then grind it.  The number of surfaces it uses to deliver that design are of very little consequence.  In certain lenses with the design moulded the design is set with a slight ability to make modifications, the back surface can still be used to clean up certain aspects but customized is not a term that I am comfortable using with these lenses.  

DVI, already has an aspheric module for their lab software, right now it is only being used as a SV lens option but at any point the light switch will flick in the mind of a lab and they will start putting aspheric/atoric surfaces on the back of that VIP mentioned and all of a sudden instead of a small number of the VIP's being delivered with their initial intended designs every VIP coming out of that particular lab will be a clean version.  Essilor supposedly has a 360 version of their natural/adaptar/smallfit coming out (according to LC @ eyeoverheard.com) won't be long before we see all current designs being cleaned up and DS becoming more a lab process than a vendor specific process.  For instance the DVI module with the aspherics/atorics if applied to any lens blank can potentially improve it, so if I apply it to a Physio I can't call it an enhanced or a 360 since these are vendor specific processes but I can call it improved.  I can't wait to see a digital option for any PAL.

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## Robert Martellaro

> Hoya and Zeiss both use spherical blanks and then modify the front and back surfaces (I really need to message Darryl and have him explain it better, at least for the Zeiss lenses.)


The Lifestyle iD doesn't use a spherical front. The iD might still be surfaced on bothe sides.




> Free Form = Blanks begin as a spherical front surface blank. Each lens is customized by individual Rx.


Freeform is a manufacturing process or platform, capable of complex surfaces that are cut to polish. Some are not optimized in any way, others have some degree of optimization, very few are highly optimized and customized. 




> Shamir and Seiko designs modify only the back surface, while Hoya and Zeiss designs modify the front and back surfaces.


I believe the Gradal individual had the front surface worked with freeform generators on some powers, probably the high plus. Pretty sure the newer Individual uses semifinished spherical blanks.




> Digitally Surfaced = Conventional molded blank surfaced on a Digital generator. Some lenses, such as Essilor's Enhanced designs, are also run through specific software to improve Rx accuracy.


I don't think we need a sub category for this when you consider that all the equipment we use today is CNC digital devices. 




> Why don't they look better in the lensometer?


You mean the Hoya lenses? They're very soft designs with more surface astigmatism near or above the 180. Look at the mires with the lenses centered on the fitting cross- they should look blurry. Now look at a VIP or SuperNoline the same way. One might say the VIP is a better lens in the distance (and if you have much larger than normal pupils it might be!). However, we don't measure the distance power at this point because the larger aperture of the lensometer samples too large of an area around (specifically below) the fitting cross. I know of more than a few doctors and opticians who choose lenses based on the above test! 




> We've reached a point where FF, DS, HD, etc don't matter. <snipped> it could be made better if the Rx being grinded included aspherics to improve the optics and deliver the intended design.


Right. It all depends on the type and degree of optimization and customization, and for PALs, the quality and specifics of the fundamental design. Good luck digging for information on which lenses do what, although Zeiss seems to be the most upfront with detailing their optimzations and lens design. 




> The number of surfaces it uses to deliver that design are of very little consequence.


That seems to be the CW. Expensive (read tricky) with little payback. Moreover, placing the progressive on the back surface offers very little advantage to the wearer, although it does make optical sense to work and optimize the surface with the most curvature (back for myopes, and the front for hyperopes.) Presently, I've decided to use backside PALs for myopes and mild hyperopes, and optimized semifinshed PALs for moderate and high plus.

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## AWTECH

I know the answers in this thread, it is the questions that are challenging.

A spherical front surface lens has many advantages, including base curve can be selected to match the frame.  As for decentration, I believe at ICE-TECH we have a great deal of decentration experience.  We produce wrap arounds with a effective diameter of 99mm +.  As Robert stated decentration causes the machine mechanical components and software to be strained.  With the right design you can make an excellent sunlens using freeform to fit almost any frame.

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## Rajkumar

Hi Mr.shanbaum
i might be asking some silly question 
is that means we will have large balnk options for freeform lenses?


Raj

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## shanbaum

> Hi Mr.shanbaum
> i might be asking some silly question 
> is that means we will have large balnk options for freeform lenses?
> 
> 
> Raj


If a lens design system does not offer decentration of the surface matrix, then there are likely to be orders on which larger blanks are required than would be required if the LDS did offer it.

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## AceOfSpades

IC UC, Shamirs Spectrum, Auto2 and FreeFrame are all true freeform, ground from a s/v blank. They can decenter the lens as much as needed. You can work on 73mm longest frame diagonal (using a 75mm blank) will cut out regardless of the PD.

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## shanbaum

Not "as much as needed." Most LDS systems impose a limit which varies by power; the cutter assembly in a generator can only move so far, so fast before it begins to introduce unwanted artifacts on the surface, and the required movement increases with decentration (especially minus lenses).

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## AceOfSpades

what ancient machines ar you using?????

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## shanbaum

The usual ones - but maybe they run better upside-down.

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## DocInChina

> The usual ones - but maybe they run better upside-down.


Hi R, that one took me a minute.  :Biggrin:  Hope all is well. E

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## DFEC

Any opinions on the Unity FF lens?  I have been talking to Perfect Optics and they are pushing the current VSP promo on the lenses.  I have never fit them and really not aware of the benefits or pitfalls of the lens.  Any input is appreciated.

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## EyeMaster

Unity FF is Shamir Technology (Autograph II like design)

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## sharpstick777

> They told me they use spherical blanks, so i would asume they would have the ability to decentre the progressive which is seemingly not the case. How do you ascertain that they have in fact used/made a freeform lens? Anyway of a quick check?


Many Free-form makers don't allow decentering because it increases the likelyhood of unwanted prism or reduced yields.  If I have machinery that cost 2 Million, I would want to keep my yields high by making sure as many lenses as possible came off the line OK.

Some Free-form manufacturers use pre-marked blanks to reduce laser time as well.  They cant be decentered.   Although Decentration is possible, it increases the chance of unwanted prism and the tool falling off the blank.  There are also blocking issues as well.  Its a business decision to keep speed and yields higher.

If you want to check, what is the name of the lens?  You can check it on Lensguru.com

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## Roscoe

I'm not sure how many folks out there will benefit from this, but I recently came up with the following information for staff training purposes...and to assist in patient education. It was my attempt to address the confusion surrounding freeform and digital lenses. I titled it "Understanding Digital and Freeform Lens Technology" and it's available in PDF form (with more details and brand-specific examples) if you're interested.  Enjoy! -Roger Smith

*Q: What is a "digital" lens, and what makes it so special?*
_A:The term "digital" refers to a newer and advanced PROCESS of surfacing a lens. A digital generator uses a computer-guided lathe that cuts and polishes the lens in one step utilizing a diamond point. This process yields a lens that is more accurate and made in less time than was previously possible with traditional lens manufacturing (which uses molds, a rougher cutting instrument, and a series of sanding/polishing stages). 

_*Q: What is a "freeform" lens, and what makes it so special*
_A: In short, a freeform lens is "unique, ONE-OF-A-KIND, and notcookie-cutter". However, what makes it ONE-OF-A-KIND involves the 1) PROCESS and 2) DESIGN compensations. 
__- PROCESS: Every SV and PAL freeform lens utilizes the digital lathe process for part or all of the lens
- DESIGN compensations: This relates to computer software which provides instructions to the digital lathe generator. The software will create customized instructions for all SV and PAL freeform lenses based on lens shape and size (frame info). However, there are more sophisticated freeform designs which will incorporate optimized prescription information (i.e. Zeiss iScription), and the most sophisticated freeform designs will generate a compensated prescription & lenses based on all of the above PLUS the patient's "position of wear" measurements (panto, wrap, vertex).

_*Q: So, in a nutshell, what's the difference between "digital"and "freeform"?*
A: "Digital" refers to the precise, computer-driven, diamondpoint lathe. It precisely and accurately follows the computer'sinstructions. "Freeform" refers to the computer programthat compensates the lens Rx and design before it gives thoseinstructions to the digital generator/lathe.

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## Roscoe

One more note...my Shamir rep told me today that all semi-finished lenses have the laser engravings on the front of the lens, and all "fully freeform" lenses have the laser engravings on the back of the lens.  Just an FYI!

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## RT

That is true for backside PAL designs, but a dual surface PAL may have markings on front, back, or both.

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## Darryl Meister

> _In short, a freeform lens is "unique, ONE-OF-A-KIND, and notcookie-cutter". However, what makes it ONE-OF-A-KIND involves the 1) PROCESS and 2) DESIGN compensations_


Keep in mind that _free-form_ technology is ultimately just a manufacturing process; it does not imply that free-form lenses are unique or "one of a kind," although some lens suppliers may have you believe otherwise.

Unless the lens design has been specifically customized by lens design software, using design input parameters specific to the individual wearer, there is little if any inherent visual benefit to free-form technology for the wearer. And it is equally possible to make traditional progressive lenses using free-form surfacing by simply adding the basic lens design surface to the back Rx surface.

Best regards,
Darryl

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## sharpstick777

We can't fully understand Free-form until we understand the problems associated with traditional grinders in progressives:

DIGITAL: We use tools/laps to grind lenses, essentially with sand paper.  On manufacturing, the average tool discrepency from true is .07 D, which means that even if I have the correct tool/lap the job starts off .07 D on average.  A fully stocked lab has over 4000 tools, and if I have 1000 jobs in process it means half my tools/laps are missing at any give time.  So I take my tray to the tool room, and my lab ticket gives me the best tool, the second and third best tools for that job.  So I might be able to substitue a 1.67 tool for my CR-39 lens in a different power, but its not perfect.  We start substituting tools for a lot of jobs.  Of course I can make a tool, but that means I have to take a job off a generator to make a tool, slowing everything down (there is no money in tools).  Or it could wait, and wait.  And that post-it I left in the empty tool slot gets thrown away on Friday at 4pm.    So that means in most cases we substitute, and most cases that tool is off power.

A free-form generator has only one tool/blade, its always there. It self calibrates daily and it tells me when the tool/blade is about to wear to the point its no longer good.

FREE-FORM:  With ground lenses we have to make compromises.  In a progressive, if I stocked every material, every add power, every Transistions or Polarized option, gray and brown and every base curve, I would need over 24,000 blanks.  Just for one brand and model.  We cant afford that so we start cutting corners, and the first thing we start cutting is reducing base curves from 45 to 5-6.  Do you know from among those what factor has the greatest effect on DVA?  Base curve.  So when we stock only 5 or 6 base curves we only give 5 or 6 RXs perfect optics, everything else is a compromise.  The first thing free-form lenses did was modify curves to give every lens the possibility of true/best form optics.   Oblique Marginal Astigmatism is also a base curve issue really, affecting cylinder and astigmatism the same way.  Only with Free-form optics can we solve base curve issues and give the patient a customized atoric back-side curve.

So with Digitial Processing and Free-form optics we in one fell swoop solve the 2 most eggregarious problems caused by ground lenses and traditional cast blanks.

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## sharpstick777

Darryl, when you say "parameters" do mean Panto, Vertex and Face-form?  Or something else?




> using design input parameters specific to the individual wearer, there is little if any inherent visual benefit to free-form technology for the wearer. And it is equally possible to make traditional progressive lenses using free-form surfacing by simply adding the basic lens design surface to the back Rx surface.
> 
> Best regards,
> Darryl

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## Darryl Meister

> Only with Free-form optics can we solve base curve issues and give the patient a customized atoric back-side curve.


As I said, this is only true when free-form surfacing is utilized in conjunction with real-time lens design software that is capable of designing or optically optimizing a new lens design using input from the wearer, prior to fabrication. Otherwise, none of the advantages that you described really apply.

Again, "free-form" or "digital" surfacing is just a lens fabrication technology. Although free-form surfacing can serve as a _vehicle_ for the production of customized lens designs, as a surfacing technology it provides no _inherent_ visual benefits to the wearer.

Not all free-form technologies involve customized optics. Consequently, while many eyecare professionals are charging their patients an added premium for "free-form" lenses, the lenses that they are selling may or may not actually offer any real visual benefits to the wearer.

I would always recommend a critical review of the lens manufacturer's patents, white papers, clinical studies, and other technical details in order to understand what your free-form lens brand of choice is providing to your patients in terms of clinically-relevant visual benefits.




> Darryl, when you say "parameters" do mean Panto, Vertex and Face-form?  Or something else?


When designing a truly "modern" progressive lens, optical ray tracing is typically utilized to improve optical performance for the wearer by modeling the lens-eye system. Minimally, this process requires a prescription, the position of wear of the lens, and the reading distance.

For semi-finished lenses, an average position of wear for a median spherical prescription is typically assumed in order to deliver sufficiently good optical performance for broad categories of wearers. With _fully customized_ free-form lenses, on the other hand, the values associated with the actual wearer can be utilized.

Furthermore, for the more sophisticated real-time lens design applications, additional factors may be utilized to customize the lens design and the distribution of progressive optics for the wearer in other clinically useful ways, such as the fitting height, lifestyle, head movement propensity, et cetera.

Best regards,
Darryl

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