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.

[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.

[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.

[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?

[Mauro.Airoldi]

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

[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.

[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.

[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.

[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?

[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.

[Bill Mahnke]

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

[jcamp]

Why don't they look better in the lensometer?

[sharpstick777]

Why don't they look better in the lensometer?

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

[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.

[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.