Free Form Generating

[skirk1975]

I would like a "simple" explanation from someone on the free form generating process. What it is and why it is good. Also, it was my understanding that there are some differences between lenses like the Zeiss Individual and the Shamir Autograph and certainly between them and the J&J Definity. What are these differences because some are lumping them in the same category.

I just need some good explanation of this new technology as I am getting some conflicting reports. Anyone had any luck using them?

[Laurie]

Freeform Technology

Hi Skirk1975,

I'll give it a shot:

Freeform technology is the process of creating a design (PAL) on the back surface of a lens. I think the best way for me to describe it is to compare it to present methods of manufacture.

Current molding technology is done in the following manner:

1. A lens designer (PhD mathmetician/physicist/engineer type) designs a concept. This includes complicated mathematical formulae that creates the design, or topography. This is the PAL design.

2. A ceramic mold is made, with the design molded on the back (inside) of the front surface.

3. A glass mold is created from the ceramic mold

4. Liquid polymer/plastic is shot into the glass mold, and the result is a semi-finished lens blank with the PAL design on the front surface. Some manufacturers invest in many molds and limit their usage for best quality, others invest in fewer molds and over-use them.

5. A generating lab surfaces off the back surface (either one spherical curve for a spherical Rx, or two curves for a cylinder Rx. This adds the patients Rx to the PAL design.

Contrast to Freeform Technology:

1. The lens designer creates the design as before, designing "lenses in the virtual".

2. The lab optician reveiws a design, and in some instances, can manipulate it for the best visual results for their particular patient's Rx.

3. Once the lab optician is confident that the design will work out, they "press a button", and a 3-point file system is downloaded via electronics to the generator.

4. The optician pulls a spherical based semi-finished lens blank (like a +6.00D, for example) and places it in the generator.

5. The generator downloads the point file system previously created, and with a full diamond lathe, cuts out (or surfaces away) both the PAL design, and the spherical and cylindrical and Add component of the original Rx. This is all done on the back surface.

Advantages:

1. Bringing the design to the back surface of the lens brings the optics closer to the eye. This is a huge improvement, as when we moved away from plus cylinder design to minus cylinder designed lenses...(no I am not talking about transposition to the Newbies....) The oldies (like me) will remember: we used to make plus cylinder lenses...that is, the toric base curve and cross curves were on the front of the lens. When I entered the field in 1979, we were still switching people over from plus cyl to minus cyl...The adaptation was a big issue, however, the visual performance was much better in the long run.

2. Bringing the optics closer to the eye cuts back on specular aberrations and increases the visual field of view.

3. Lens manufacturers who have been in the mold business for years (like Shamir) have a distinct advantage...this technology is not new to them...they are quite experienced with it.

4. No more duplication and using molds over and over. (as in any duplication process, the copy gets watered down after several duplications).

5. No more mailing hockey puks (semi-finished lens blanks) around the world.

Does that help?

:)

Laurie

[Laurie]

differences between Zeiss, Shamir and J & J

Hello Again,

I forgot to address your other question.

Main differences:

Manufacturers who are involved in Freeform Technology still adhere to their design concepts. A great PAL design on the front surface will be even better on the back surface.

If the design is not great to begin with, bringing it to the back surface will not enhance visual performance that much.

I am not an expert in the Zeiss design...someone else may want to jump in on that. I believe that it is entirely on the back surface.

I do know that the Shamir Autograph is completely on the back surface, and the J & J design is on both the front and the back (a split design, if you will).

My criteria for a great design would be:

1. No more than 0.50 D or less marginal astigmatism/excessive cylinder at or above the 180 line. I would actually place a mm rule across the fitting cross out to the 180 meridian dots to be sure. (This can be done on the topography contour plot provided by the manufacturer).

2. A 1:1 ratio (or less) of excessive cylinder. That is, the excessive cylinder/unwanted induced surface astigtmatic error will not exceed the add power anywhere on the lens surface. (look at the numbers on the contour plot to be sure) And, I would want to see a topography./contour of a +2.50 - +2.75 Add power...not just in a +1.00 or +1.50 Add.

3. A FULL add power (not 80 percent) in the near, and at least 5 mm vertical dimension.

4. Multi Design

5. Asymmetric and Triple Aspheric

6. Mulitple options of molds for various base curves and add powers

7. Limited usage of molds

8. Available in TRIVEX for drill mounts.

: )

Laurie

[Robert Martellaro]

Another advantage is that the back curve is atoric, which minimizes oblique astigmatism, especially for higher cylinder Rxs. In addition, higher minus Rx lenses will be a bit thinner than aspheric only front curves.

[Bev Heishman]

Spectacle Lens Group , J & J Definity uses a Dual Add. The add is split up with some being on the front side and the remainder being on the back side. Tradional PAL's are generally molded and made aspheric in the add area only. Some manufacturers minimize the peripheral areas by making the lens aspheric throughout. Newer designs and free form can also aspherize the toricity increasing patient acceptance. Spectacle Lens Group has defined the peripheral differences as the 4th zone.

SLG's Definity with the dual add design and the aspheric/atoric features appears to have lower levels of astigmatism or distortion in the traditional areas that are normally defined by Minkwitz's law which means that a 1 D add will produce 1D per diopter of astigmatic design per diopter (+ or -20%) which can vary if I am recalling correctly.

Costs vary among free form progressives. Our own experiences as professionals and the response by our patients as well as price, has allowed us to position the Definity as our premium progressive.

[Darryl Meister]

I think we should clarify a few points here, since I have seen several references to manufacturer-specific, proprietary technologies instead of general statements regarding free-form manufacturing. "Free-form" has become somewhat of an industry sound-bite that is often misunderstood. First, it is important to remember that 1) "free-form" doesn't necessarily mean "better" and 2) not all free-form implementations are the same. That said, let's consider why free-form can be better...
In the traditional model of semi-finished lens production and delivery, the basic progressive lens design can only be varied slightly for each base curve and add power combination in order to tailor the performance of the design for broad categories of wearers. Typically, for instance, a semi-finished progressive lens blank is "optimized" (or optically tailored) for a spherical Rx near the center of its base curve prescription range. This becomes a serious performance limitation when prescriptions other than this median sphere power are used on the lens blank.

Consider the optical blur produced by this design for a low-minus prescription:


Low Myope

Versus the performance of the same lens design for a prescription with cylinder power:


Low Myope with Astigmatism

Note the restricted optical performance, particularly in the near zone, and the translation of the distance zone.

But what if you could design a lens for every job, not just a median sphere Rx in a typical frame? Free-form manufacturing is simply another method of manufacturing, not entirely unlike the manufacturing process we already use for metal molds (used for polycarbonate progressive lenses). However, free-form manufacturing frees us from the constraints of semi-finished lens design, and allows us to design lenses in "real time" or "on-the-fly" for a wearer's specific prescription and frame fitting parameters. A unique progressive lens can be custom designed for each individual wearer.

This can provide substantial optical benefits to the wearer. Essentially, free-form technology allows us to consistently design the progressive lens around a given wearer, not just an average prescription, ensuring that all wearers enjoy the intended optical performance of the lens design.

However, it is important to note that the use of free-form manufacturing does not necessarily mean that the lenses are any more sophisticated or any more "fine-tuned" for a prescription than lenses produced from semi-finished lens blanks. That is to say, not all "free-form" processes produce lenses that are superior to their semi-finished counterparts. And some may be only marginally superior. While the clever application of free-form technology opens up an infinite universe of progressive design possibilities, the performance advantages of these designs will be limited without an innovative optimization strategy or sophisticated computer software.

It is also important to remember that, while free-form technology is often used to improve the performance of a lens design, it generally won't turn a "bad" design into a "good" design. Consequently, you should be confident in the performance of a given lens design before you can expect much from its free-form counterpart.

You may also want to refer to this thread for a rather lengthy discussion of free-form technology.

Best regards,
Darryl
(SOLA)

[Laurie]

freeform...

Great points, Robert Bev and Darryl,


I want to emphasize what Darryl wrote...a good design is better with freeform manufacturing technology, however a mediocre design will not suddenly become great.

As opticians, we still have to stay on top of differences in designs and do our homework. We can't bunch all PALs into a "freeform" mold (pun intended).

: )

Laurie

[Bobie]

Shamir Autograph vs Hoyalux iD

In Thailand , we are going to test Shamir Autograph vs Hoyalux iD and will report in this board on March 2007. ( Test on the wearer for 120 days ).

[AWTECH]

Freeform testing

Bobie said:

Test on the wearer for 120 days

I appreciate your effort to compare lens designs but a test for 120 days on one person will not produce any meaningful test.

In your country Thai Optical has been producing a freeform lens with excellent results for over one year. Adaptation on a great design is 99% plus.

[Bobie]

TOG Excelite Freedom : Free Form Aspheric / Progressive Back Surface

Dear AWTECH ,

We have been test more than 1,000 clinical study of TOG Excelite Freedom : Free Form Aspheric / Progressive Back Surface and we are agree with you in the great performance of Excilite Freedom.

We also have been test Excilite Freedom 13 & 15 on trial frame from Plano ADD 1.00D up to Plano ADD 2.50D with more than 3,000 wearer and the performance is still greater than all semi-finished PALs more than 40%.
( Our PALs centre have more than 20 models of difference PALs trial lenses set that design to test on Trial Frame adjustable P.D./PTA/CVD )


We think , Free Form Technology is the future of PALs that can kick semi-finished Rx PALs out of market within 10 years.

The Excelite Freedom 13 - 1.6/42 MR-20 is one of the best PALs for small frame because the corridor 13 mm that have greater performance at intermediate than corridor 11 mm.

The problem of Excelite Freedom is the deliver time , because of over demand of customer. Sometime we have to waiting more than 3 weeks.

[RGC_man]

My former company recently trialled these, and of the couple of dozen we saw not one didn't have some problem, from powers, to coatings, to surfacing marks, to just being weeks overdue. They may iron out these issues in time, but I would expect more when paying £400 ($750) retail just for the lenses.

[Echo419]

If somone owned a copy of the software or a corporation who is heavily in the eyecare retail market, purchased the rights to the software, could'nt they produce high quality progressives at the cost of SV blanks?

[AWTECH]

Cost

Echo419 said:

If somone owned a copy of the software or a corporation who is heavily in the eyecare retail market, purchased the rights to the software, could'nt they produce high quality progressives at the cost of SV blanks?

With your logic many items that cost money could be free. An example below:

Yes they could and you can provide their eye exam for free once you purchase your building, purchase all of your office equipment, purchase your office furnishings, pay for your schooling to become an OD and work for free.

If you can not pay for all of your costs up front and you have to get a mortgage on your building, I am sure you won't mind getting a part time job to pay the morgage payment so the patients can still have their free eye exam.

How is anyone going to know that you offer free eye exam's unless you purchase a sign and/or do some advertising?

[Echo419]

I'm not implying that the lens should be free? or even cost the end users the same as a sv. A wholesale lab has every right to charge what ever they deem the value of their time and product is worth. I realize that the material cost of the blank is not the value of the finished product. Orthodontist charge 3,000.00 and up for braces, no one concludes thats the cost of the wires and rubber band? I'm just saying that with technology we have all witnessed that somethings have dramatically dropped in price because production costs dropped. Computers, microchips, contact lenses.

[AWTECH]

Echo419 said:

I'm just saying that with technology we have all witnessed that somethings have dramatically dropped in price because production costs dropped. Computers, microchips, contact lenses.

Your right at some point the costs on freeform products may come down but for this to happen the market penetration must be pretty high.

Volume is the key to lower prices. For now the percent of freeform lenses in the US market is less than 1%. I think AR is at about 20% and premium AR is still expensive, probably about 10%.

So for now if you want a better lens product such as a great optimized individualized freeform design you must pay the current price. If you would like to learn more about freeform lenses and their benefits private message me or e-mail me, (aweatherby@ice-tech.com), and since you are in Florida during one of my travels in your area I can stop by.