How does Free-form chalenge us?

[QDO1]

Consider this RX, as written...

R -6.00 - 2.00 x 45 2 base IN
L -3.00 -2.00 x 135
Add + 2.00
"Please dispense progressives"
Signed: Joe Blogs MD

So you think about it...
Clearly the patient is:
Just about aneisometropic, has oblique cyls, and is a moderate myope

A discussion with the patient confirms the need for a multi-purpose pair of spectacles - he works in a shop, selling computers, typing up orders, and serving customers all day long, and often multitasks

In the first instance, this looks like a perfect example of a RX for free-form progressives, where the free-form optimisation, can go some way to alliviating some of the problems this type of RX poses

What do we do next? What other info do we need from the practitioner, who is not in the building?

So eagerly we run off and (for no other reason than its the first one to come to my mind) grab that ILT order pad the Rodenstock rep left behind

It asks you for

• Test BVD
• The order and power of the lenses in the trial frame including the prisms
• How you want the prism split up
• How much the patient converges

and

• The dihedral angle of the frame
• Frontal angle
• BVD for the dispensed frame
• Mono OC's
• Mono Heights

Now we are stuck. To start off with (to my mind) the BVD ought to have been on the original order. The other information (to do with the test) is not available. How many "regular dispensers" would struggle with the dispensing measurements.. the implication on the form, is that they want them pretty accuratally

The industry as a whole is not set up to deal with this sort of free-form technology - and thats pre-order. This technology is what we all have, available in our practices today, and it is allready being "demanded" by patients. Some are calling them the "ultimate lenses", but at the moment, unless the refractionist is doing the whole job "from refraction to dispensing and ordering", or, if the dispenser is working hand and glove with the refractionist... the process stops

what practitioners need to do is start recording this type of information, if they have a slight idea that this sort of lens may be used in the dispensing. what dispensers will need to do is learn how to measure all of the new measurements (that most) dont ever measure for anything

The lens manufacturers are throwing down a chalenge to us

[William Stacy O.D.]

This technology is what we all have, available in our practices today, and it is allready being "demanded" by patients.

That's a stretch, at least for Folsom CA, a pretty high tech neighborhood (my office is walking distance from Intel's big plant-7000 geeks). I've been fitting progressives for 30 years, have a lot of progressive wearing patients, and have never had one even ask about free form techology. No doubt the use of this technology will increase (and should), but there's a LOT of inertia out there...

[AWTECH]

How do you order a Freeform lens?

First all freeform technologies do not need the same information.

My company has developed freeform designs. We are currently developing more and to handle the ease of use for the optiician we are requiring the frame be either one of ours (ICE-TECH), or to send any other frame to us at ICE-TECH Rx. Our remommendation is to dot the pupil and submit the standard Rx. We measure the frame, make the necessary calculations and will return the completed frame and lens ready for delivery to the patient.

Some freeform designs do not require frame angle information making them not quite as individualized.

[Cherry Optical]

Now we are stuck. To start off with (to my mind) the BVD ought to have been on the original order. The other information (to do with the test) is not available. How many "regular dispensers" would struggle with the dispensing measurements.. the implication on the form, is that they want them pretty accuratally

The industry as a whole is not set up to deal with this sort of free-form technology - and thats pre-order. This technology is what we all have, available in our practices today, and it is allready being "demanded" by patients. Some are calling them the "ultimate lenses", but at the moment, unless the refractionist is doing the whole job "from refraction to dispensing and ordering", or, if the dispenser is working hand and glove with the refractionist... the process stop

Not to be obtose, but perhaps you should schedule an appointment with your lab rep to talk about the proper ordering procedure and fitting of Free-Form lenses. If he can not help you, I would suggest firing him and calling someone else who has spent time learning about new technology.

All labs are not equal. Most do a great job of making the same lenses they have been making for the past 100 years. Few have taken the bull by the horns and learned to manufacturer and process the latest in lens technologies. I

Adam

[HarryChiling]

and

• The dihedral angle of the frame
• Frontal angle
• BVD for the dispensed frame
• Mono OC's
• Mono Heights

In opticianry in the US we refer to the dihedral angle "the angle formed between two planes" as the tilt, is it called the dihedral angle where you practice?

[QDO1]

In opticianry in the US we refer to the dihedral angle "the angle formed between two planes" as the tilt, is it called the dihedral angle where you practice?

no - thats what Rodenstock call it

[QDO1]

Not to be obtose, but perhaps you should schedule an appointment with your lab rep to talk about the proper ordering procedure and fitting of Free-Form lenses. If he can not help you, I would suggest firing him and calling someone else who has spent time learning about new technology.

All labs are not equal. Most do a great job of making the same lenses they have been making for the past 100 years. Few have taken the bull by the horns and learned to manufacturer and process the latest in lens technologies. I

Adam

I wasnt saying I had any problems measuring and fitting them. Infact I have fitted many. I do have problems with getting the measurements needed from whoeever did the refraction (those measurements specific to the refraction).

My experience with most other "dispensers" in the industry (note lack of the words qualified or experienced or both) is that they would struggle with the measurements

[QDO1]

First all freeform technologies do not need the same information.

This is an interesting observation. It seems that Free-form is a catch-all type phrase, that describes a certian type of process - It does not however garuntee the quality of the result of the process is comparable between manufacturers or designs

The word "aspheric" is a similar word. everyone expects "aspheric lenses" to deliver "thinner lenses with superior vision", whereas Aspheric simply means "not spherical" - An aspheric lens could be thinner/thicker and/or with better/poorer optics

I am always a little wary when a new technology buzz word is touted as the "way to go" or the "latest best thing". I think the quality of a free-form lens is only as high as the quality of the information (measurements etc.) supplied in conjunction with the quality of the algorythm generating the final design

[William Stacy O.D.]

In opticianry in the US we refer to the dihedral angle "the angle formed between two planes" as the tilt, is it called the dihedral angle where you practice?

Now I'm confused. When you say "tilt" you are NOT referring to pantoscopic tilt, but the angle of "wrap"?????

[AWTECH]

A good lens takes more than Freeform

This is an interesting observation. It seems that Free-form is a catch-all type phrase, that describes a certian type of process - It does not however garuntee the quality of the result of the process is comparable between manufacturers or designs

The word "aspheric" is a similar word. everyone expects "aspheric lenses" to deliver "thinner lenses with superior vision", whereas Aspheric simply means "not spherical" - An aspheric lens could be thinner/thicker and/or with better/poorer optics

I am always a little wary when a new technology buzz word is touted as the "way to go" or the "latest best thing". I think the quality of a free-form lens is only as high as the quality of the information (measurements etc.) supplied in conjunction with the quality of the algorythm generating the final design

You have nailed the point I was trying to make. In addition to having any piece of equipment it is necessary to have skilled operators.

With computers driving the lens manufacturing; freeform machines the operator of the CNC freeform machine, is to a large degree, the lens data generated that software. This software now becomes the operator of the machine. (The actual loading of the lens into the machine to make the lens is even automated in many cases.) "No humans needed here". Where great humans are needed in the process, is in the data entry and the software design and development. The final skilled human needed is the fitting optician. The optician is needed to make sure the fame is properly adjusted and the patient knows how to use the product being fitted.

[Pete Hanlin]

Direct-to-surface (aka, freeform, 360 Digital Surfacing, etc.) processing of lenses is simply a new way to make ophthalmic lenses. True, it is one which expands the potential forms a lens may take, but in the end it still comes down to the design of the lens.

Darryl Meister has written an excellent article on this topic which may be downloaded from this website.

The additional measurements required by some lenses inform the additional parameters possible with direct-to-surface lenses. In a way, by providing extra parameters regarding the fit (or the wearer him/herself), you are providing a more precisely tailored finished product to your patient. However, other lenses may benefit from the advantages of the direct-to-surface process without additional measurements.

Some manufacturers, like Rodenstock and Zeiss, have elected to compensate for the "as-worn" position of the lenses. Therefore, they ask for the panto, wrap, and vertex measurements. Some lenses are personalized to visual habits of the wearer (e.g., Varilux Ipseo, which incorporates measurements taken with the Vision Print System). Some lenses are informed by lifestyle questions- such as the Seiko Super Proceed 1 Internal.

There will doubtless be many many designs that arise from direct-to-surface technology. Choosing the ones you dispense will require an understanding of a.) what the technology is really offering by way of advancement, and b.) what is required to properly fit the lenses.

Varilux Physio, which Essilor just launched, benefits from direct-to-surface technology on the front (design) side of the lens. Using direct surfaced molds (Essilor's name for the process is "360 Digital Surfacing"), the wavefront is controled as it passes through the lens to the eye- eliminating higher order aberrations commonly found in PAL lenses. However, no additional measurements are required- the design "gain" is in the optimization of the front design (and greater accuracy of the molds). Varilux Physio 360 is also digitally surfaced on the back side- to preserve the progressive design against the distortion caused by the patient's distance Rx (which is commonly surfaced on the back of the lens).

[AWTECH]

Physio & 360 Explaned? Plus a few questions

Thanks Pete for the information about the Physio and the 360.

I can now understand the marketing of the Physio. What your company is claiming is that the mold quality is digitally controlled. This is the same basic approach to making a freeform lens on the fly.

The fact is digitally controlled molds for progressives is not new technology. Many progressive designs are made with digetally controlled mold equipment. The main difference in the equipment is the time needed to cut a progressive metal mold is hours not minutes.

It is back to the design of the lens that is important. For example I would like to know how many different combinations of prescriptions are available for the Physio and how many for the 360.

In general there are about 1/2 million combinations of Rx's I would guess for the the front cast lens and for the 360 back freeform I would guess their are almost 1 million or possibly more.

These numbers are just a guess since I have not seen how many blanks are offered nor do I have the rx ranges available.

[HarryChiling]

Now I'm confused. When you say "tilt" you are NOT referring to pantoscopic tilt, but the angle of "wrap"?????

Actually both would be considered a dihedral angle, the plane that would be the major reference would be the plane that the patient is refracted on in the phoropter. Any change to this plane is going to induce cylinder and change power as well as the axis. Panto, retro, face form, wrap, these are all changes to the plane the Rx lens sits on and the angle of change is called the dihedral angle. You can check the effects of tilt to lenses with Darryls Rx Compensator, or even dowload my equation calculators from the files directory.

As for the benifits of a lens with free form front surface that can be generated on the back with conventional machines. It does offer additional benifits, take for example a 6 base lens with a 3 add. The umbilic on this lens would be very narrow, however with the technology to control the lens parameters on a point by point basis across the lens surface you have the opportunity to widen or increase the umbilic and offering more visual real estate if you will, and since a 6 base is going to fit a range of Rx's from +2 to -2 it does give you a ball park as to what the Rx in this lens is going to be so that you can make front surface changes to help control abberations such as marginal astigmatism.

The difference between the Physio and 360 is that the physio is going to assume that you are going to use the power within the base curves parameters and is optimized for the abberations using this ball park figure on the front surface, where the 360 design would allow the ball park figure to be optimized even further on the back surface with additional curve changes. This would allow essilor to customize an Rx without having to make a million different molds.

[QDO1]

the dihedral thing throws up a interesting point

Dihedral - wrap - faceform ... are all considered by different professionals to mean the same thing (it just depends if you are in Germany, the UK, or USA) problem is, the Germans sent the orderpads + literature with the word "dihedral" on to the UK. It confused us for a while untill we sussed out what they really wanted

[William Stacy O.D.]

the dihedral thing throws up a interesting point

Dihedral - wrap - faceform ... are all considered by different professionals to mean the same thing (it just depends if you are in Germany, the UK, or USA) problem is, the Germans sent the orderpads + literature with the word "dihedral" on to the UK. It confused us for a while untill we sussed out what they really wanted

I got confused because:

Originally Posted by HarryChiling
In opticianry in the US we refer to the dihedral angle "the angle formed between two planes" as the tilt, is it called the dihedral angle where you practice?

and I thought he meant pantoscopic "tilt", but his last post was completely ambiguous on what dihedral meant in ophthalmic optics. If I understand you, it refers to the angle between two lenses, commonly known as "wrap", rather than panto. Or am I still confused?