We use the Physio here and no one has complained about that one. The Physio Enhanced does poorly here for some reason and any measurement is never dropped. That confuses me still.Originally Posted by Happylady
We use the Physio here and no one has complained about that one. The Physio Enhanced does poorly here for some reason and any measurement is never dropped. That confuses me still.
We are going to give the Auto III a whirl and see how it does for us. Thanks for the discussion
Clinton Tower
The intellect to live free is in short supply
ALT248=°
Some wise person on this board once wrote "All Free Form lenses are Digital, but not all Digital lenses are Free Form." And no, that person wasn't me.
So, here are the different manufacturing processes, regardless of what you want to call them, as seen from someone who works in a lab that does most of them:
Front side molded conventional progressive, digitally optimized back surface. Examples: Hoya iQ series, Essilor 360 and Enhanced series
Front side molded progressive design, with partial add power, digital back surface with remainder of the add power. Example: Essilor Definity
Front side molded vertical portion of progressive design, digitally surfaced horizontal portion of progressive design. Examples: Hoya iD LifeStyle, Hoya iD Lifestyle 2
Spherical front surface lens, digitally surfaced Free Form progressive design back surface. Examples: All Shamir FreeForm designs, All Seiko Free Form designs, All IOT Free Form designs, Hoya Array
Digitally surfaced front AND back surface. Examples: Hoya MyStyle, Hoya InStyle
Now, since we don't run Zeiss in house, I have the least amount of knowledge of their lenses. Can someone please educate me on where their lenses would fall in the above categories?
There are rules. Knowing those are easy. There are exceptions to the rules. Knowing those are easy. Knowing when to use them is slightly less easy. There are exceptions to the exceptions. Knowing those is a little more tricky, and know when to use those is even more so. Our industry is FULL of all of the above.
Spherical front, back progressive for all but high plus, where both surfaces are worked. It seems likely that the front has the progressive optics, with a spherical/toric or atoric back for the high plus, up to +16.00 D.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
I've been told that a spherical front, backside progressive is functionally identical to a progressive where both sides are surfaced for everything but moderate to high plus powers. Is this true?
Pretty much.
GT23D is aspherical front surface with full backside free form surfacing.
Individual 2 is aspherical front surface with full backside free form surfacing.
The difference is in what design is placed on the lens. A GT23D places a GT2 design on the back surface, with compensated curvatures to enhance the performance of the design with a given Rx (So it attempts to eliminate unwanted astigmatism caused by the given rx where the given rx might not be ideal for the given design/BC/etc).
An Individual 2 has target performance goals in the various zones of vision that are regulated by a math formula. By supplying the rx, frame size/shape, position of wear measurements, etc., the formula is able to specify more exact curvatures necessary to meet the target performance of the lens.
Edit: Individual 2 1.74 is dual surface free form
When did they change to an aspheric front? Zeiss owns the free-world patent (USPTO 6,089,713) on multifocal back side lenses with a spherical rotationally symmetrical front surface!
Last edited by Robert Martellaro; 10-03-2014 at 06:30 AM.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Things that make me go Hmmmm.
You have never worked in a Free-form lab have you?
Only in powers greater than a +6.00 and made in Germany, its single surface free-form otherwise.
From Bruce at Optivision:
LDS = Lens Design System, or Lens Design Software, the lens vendor's proprietary custom freeform lens design software.SDF = Surface Definition File, or Surface Data File, a three-point file of the X, Y, and Z coordinates that describe the surface height across the lens surface, like a 3D picture of the surface, commonly referred to as a points file.
LMS = Lab Management System, or Lab Management Software, the lab software used at the optical lab.
The typical freeform process:
1) An Rx order is entered into the LMS Lab Software.
2) The Lab Management System generates and sends an ".LDS" file, which has all of the required Rx job info, to the lens vendor's custom freeform software.
3) From the patient’s Rx, center & edge thicknesses, and other details in the ".LDS" file, the lens vendor's custom freeform software calculates the freeform Rx, generates an ".SDF" file which is sent to a designated storage area, such as a server, that can be accessed by the LMS and the blocker, generator, polish, and laser engraver machines.
4) The lens vendor's custom freeform software generates and sends an ".LMS" file, which has the location of the storage area and the Rx details, to the Lab Management System.
5) When requested by the freeform machines, the LMS sends the data location and any other info required to the relevant machines to access the data and undertake its function in the lens production process.
Hope this explains some of this better.
Cheers,
~ Bruce
Bruce Krymow
Director, Marketing & Operations
Optivision®, Inc.
Robert, the orginal GT3D was for a short time a hybrid lens like the enhanced with the add on the front with the traditional GT3D blank, I don't know if was released in all markets (I only saw the marketing material). A short time later it was a fully Free-form backside add lens. I don't know when it switched, or if it was just misprinted marketing material. But it is the source for the confusion I assume. Technically a standard progressive blank is aspheric.
The major difference between the Auto III and the Physio Enhanced is that the Add (most of it) remains cast on the Physio Enhanced. The effect of this cannot be overstated. I am convinced the only reason that manufactures started and continued this "hybrid" digital back and cast front lens design is to avoid paying patents to Seiko and Zeiss who own the 2 patents necessary for free-form.
The optical difference are huge, because we don't truly have ANY Front side add lens (relative to the sphere power). All Progressives have a back side add as it sits in a plane behind the distance spherical power. The difference however is that the smooth transitional curves that join the distance and reading surfaces are on either the front or the back, or both. But on the front combined with the displacement of the add, the effect is huge.
yes, you can conceivable have a so called "frontside" add lens where the add power is technically behind a so called "backside" all lens. The impact on this optically is enormous. Because when the transition curves (or add power for you not catching up) is on the front, it must resolve smoothly with the spherical surfucae it NEVER intersects. The consequence of that is I will always have 2 opposite direction transitional curves.
With the add on the back however (really the transitional curves on the back) the add power is the flattest portion of the lens, and the effective spherical power is the steepest, but more importantly the plane of those curves intersect. That means I only need one transitional curve to link those two surfaces smoothly. The net result is wider fields of view, and less unwanted prism (swim or sway).
The mixed or hybrid lenses with the add (or a portion of the add) on the front end up with 3 transitional curves, 2 on the front, 1 on the back. Aligning those 3 curves precisely (although possible) is currently beyond any current blocking technology even in spherical powers. Cyl just makes that whole conversation and math exponentially messy, it would take a day or 2 to calculate even if we could block it out perfectly.
The above is easiest to explain when dealing with the potential number of possible focal points. In minus power a backside add (and transitional curve lens) will have a narrower range or cross section of possible focal points. In plus powers that number drops for various reasons, but backside transition curves hold less of an advantage in my math up to +6.00, then a front side add lens gains some traction (it has to do with how base curves are calculated in free-form vs traditional lenses). Interestingly that is where Zeiss starts moving the add to the front of the Individual 2.
So we have a few different category of lenses. I would NOT trust Essilors definition:
Digital Lenses: Processed on CNC lathe, but offer no compensated curves or backside transitional curves
Hybrid Lenses: Digital processed on back, some add on front. The add power or Location is not fully optimized. Usually distance power only on the back that might receive basic aspheric compensation (Read Essilor Physio Enhanced).
Free-form Lenses: Simple: Only basic compensations for base curve and cyl, but the add is all on the back
Free-form Lenses: Advanced: More advance compensations based on averages of panto, face form and tilt, but not optimized individually. may or may not include frame data.
Free-form Lenses: Advanced or Personalized. Similar to and advanced lens but taking the POW measurments for each person, add fully on the back. (Think Autograph III).
So the Auto III is technically many levels superior to the Physio Enhanced.
The best example highlighting the difference between various classes of 100% pure free-form lenses is:
Shamir
Element: Basic Free-form, not unlike a SV aspheric lenses, but with the add on the back. Compensations for base curve and atoricity based on a 0 fitting.
Spectrum: Fully compensated powers, distance and near, but based on averages for vertex, panto and tilt.
Autograph II & III: Individually compensated, based on individually measured vertex, panto and tilt
Last edited by sharpstick777; 09-30-2014 at 02:04 PM.
Hybrid lenses (with the Add cast the front and partly Free-form the back) suffer in a few ways. The greatest of which is that I have 3 transitional curves, 2 on the front and 1 on the back that I have to align for optimal optics. this gets tricky because I have to de-block a lens to surface both sides, or depend on the accuracy of the casting (which is very messy at best). Neither is an good choice.
These transitional curves all have differing angles, and those angles will vary depending on the cyl and add powers involved. So they can be a mess directionally, and greater unpredictability esp in peripheral vision as we move farther from the center.
So although using a dual surface design has some possibilities, aligning 3 curves with varying angles and powers of unwanted cyl that change with each effective correctives cyl creates a mathematical nightmare. And even if I could fix that, the blocking we use today would mess it all up anyway.
This is why Zeiss and Seiko have stayed away (mostly) from 2 surface designs, Shamir paid their patent fees at the beginning, and you find the only ones to make hybrid lenses are also the only ones to reach financial terms with Seiko and Zeiss after many many years of holding out.
*mind blown*
Thanks sharpstick, that was helpful. Somewhat separately, does anyone know exactly where Zeiss's Choice lens series sit?
Thanks sharpstick, most informative series of posts concerning the original topic. Hat's off to ya!
Clinton Tower
The intellect to live free is in short supply
ALT248=°
It was a rhetorical question. They use spherical SFSV blanks.
I think everyone is getting too hung-up on the progressive optics placement, whether it's molded or direct surfaced, etc. What matters is reduced aberrations, the fundamental PAL design, understanding the differences in design, how the design and functionality adheres to the intended design over a wide range of RXs and fitting parameters, and matching that design to the clients visual needs.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Zeiss's Choice sits next to Spectrum. The Choice Plus, and Choice Plus V are almost between the Spectrum and Autograph series because of the greater corridor options.
I can't speak for everyone else, but understanding how each lens functions in reality is exactly what I'm trying to do. Unfortunately there doesn't seem to be a third party research group (or even a half-assed group like Consumer Reports) that checks these things out. All I (and, I assume, others) have to go on is absurd hype from each manufacturer, and (often unreliable, at best weakly anecdotal) patient feedback.
I want a straight up, "this lens will work this way for these people" for each type of lens. I want them ranked. I want them categorized. I want them thoroughly tested. And I want all that done in a scientifically rigorous fashion, by unbiased third parties. I don't want any of this "well, it's more of an art..." crap, I want hard science.
But that clearly doesn't exist, mostly because no one cares enough to spend the time, effort, and money necessary to do it. Which is crazy, given how important a field this is. I mean, can you imagine the FDA just saying "ah well, just let that new artificial heart out on the market. I mean, sure it hasn't been rigorously tested, and all we have to go on are claims by a shady company's marketing department, but meh". People's lives depend on their eyes, but it's like no one important really cares. Heck, MY LIFE depends on the eyes of other people while they drive their vehicles.
/rant
Anyway, that's the reason why I'm here, at least. If I can't access any real research on lenses, then I have to settle for anecdotes. And if I'm going to settle for anecdotes, I want it to be anecdotal evidence from the most experienced people I can find. Which is all of you, here. It's unacceptable that I (and others) have to go to these lengths just to learn basic information about lenses, but that seems to be the way it is right now.
This should help.
http://www.youngeroptics.com.br/arqu...ient_needs.pdf
We can perform our own subjective testing also.
************************************************************ ****************
A realistic assessment of FF PALs.
http://www.iot.es/ffadvantages.html
Some highlights...
What is Free Form (FF)?
• Free form is a manufacturing technology that allows cutting and polishing arbitrary surfaces
• A lens is free-form if
- At least one of its surfaces is made with free form technology and
- That surface is not spherical neither torical
What cannot be done with advanced ophthalmic design and FF technology?
• Progressive lenses that violates Minkwitz’s theorem (PALs with wider corridors for the same corridor length.)
• Lenses without aberrations
• Lenses which compensates for third order eye aberrations at any direction of sight (those can be compensated only within a very narrow field)
• PALs without adaptation period.
• Short PALs with intermediate wide enough for computer displays.
Back-side or front-side?
• The position of the progressive surface (even if there are two progressive surfaces) is not that important.
• The important thing is the progressive surface (or both) being free-form and computed with good software, not the position.
• The performance of any front side PAL can be reproduced in a back side PAL. The opposite is also true.
• Some miss-conceptions about back-side progressives:
• “Field is wider because the surface is nearer to the eye.” Indeed the back surface is a little bit nearer, but also there is less room for progression on the back, so there is not net improvement.
• “Magnification is more stable because front refractive power is constant.” That’s true, but the effect is so small. Magnification is mainly due to power. As power increases in a PAL, so does magnification.
• “Back side PALs produces less distortion”. False. Distortion depends on the power variation. The faster the variation, the larger the distortion. This is a characteristic of the design, whether it is back of front.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Great thread- thanks especially Robert and Sharpstick.
I had always wondered how the corridors on the Enhanced series could narrow vertically if they are using the same molded blanks as Comfort and Physio with longer minimum seg heights. Any takers?
[QUOTE=sharpstick777;493790]T
The optical difference are huge, because we don't truly have ANY Front side add lens (relative to the sphere power). All Progressives have a back side add as it sits in a plane behind the distance spherical power.
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