Ok so perhaps I am missing something here.
I recall someone joking some months back about Essilor bringing out a Flat-top with digital surfacing.
I got a memo today announcing that they indeed have released it.
Am I missing something here? What is the relevance of this product?
Regards,
Golfnorth
Both Hoya STIQ FT 28 and Essilor FT 28 AB are digitally-surfaced and optimized. I use both.
B
Hi Barry;
Thank you for your prompt reply.
What prescription range are you finding fits well with the FT 28 Digital?
Which customer's would benefit the most?
Sincerely,
Golfnorth
I have not used any of these, but my guess would be for higher cyls and obliques, as they would indeed benefit the most.
We produce our ICE-TECH Digital Bifocal, it was developed to offer a better product for flat top patients. The advantages are many, for our design we optimize the back surface with an aspheric design which is not possible with traditional surfacing. We can also use our exclusive Thin-ICE patented technology to thin the edges in high powers.
any cyl power over 1D, with good acuity.
B
I've been using Hoya's Digital FT28 for most patients that require a lined bifocal with a cyl power over 1D. Fantastic product. Clearer vision = happy customers = return customers = $$. :)
Acuity is the key!Originally Posted by Barry Santini
I have more than a few clients with reduced quantity and quality of vision. The decision to use less expensive, non-optimized lens designs for some of these folks is counterintuitive, but one that I make frequently, learning from previous experience that for some of these folks, advanced lens designs offer no visual improvement over traditionally surfaced lenses, with the money saved going towards auxiliary eyeglasses for specific tasks, which frequently do improve their visual lot in life.
Available in Trivex (Phoenix) is a huge plus. Who in their right mind is going to fit a -8 D multifocal in Poly?!
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.
It was over 1 year ago, its called the FT-28 360. Ice-Tech also offers a full free-form bi-focal, the add is on the back.
Free-form round segs are also available from Three Rivers Optical and US Optical.
Luzerne is processing both the Essilor FT AB and the Hoya iQ FT28 in house.
Barry Santini and I talked about this over a year ago. It would be doable with anyone's D28 or 35 and probably trifocals too, You can use anyone's FF single vision software, the results should be superior to conventional surfacing.
Do you mean a normal bifocal front surface blank with a FreeForm digitally optimised backsurface?
The FreeForm surface on the back should be optimised for 2 different base curves (one of the far and another for the near portion).
When you have a cylindrical correction, the back surface should take into account 2 front base curves, the axis change in near (Listing's law) and make the atoric optimisation for the cylinder differently for 2 base curves.
I believe it will be hard to calculate a continuous surface making all those optimisations.
The optimisation for SV will be closely matched to a single front base curve.You can use anyone's FF single vision software
The effect on the near segment will be like having an atoric FF backsurface calculated for BC 3 and putting it on a BC 6.5 blank.
Last edited by Nikolay Angelov; 11-27-2011 at 07:35 AM.
The lack of optimization effects for near in bifocals and SV readers is an oversight with today's design algorithms. However, we're really at the stage that most POW optimizations are several orders of magnitude less important than how optimal The Rx is that you start with.
In other words, don't get carried away here by the numbers.
B
The RX is indeed the corner stone of good vision.
However i suspect that the the described "Digital Bifocals" provide worse vision than conventional bifocals in the near zone.
We know (and can calculate) the exact performance of conventional bifocals:
http://books.google.bg/books?id=Zl45...page&q&f=false
I haven't seen any data on those newly "optimised" lenses, to show they aren't inferior.
<rambling mode = on>
"Digital" is meaningless term, every lens design have a "digital" step where the surface is calculated.
Same with "optimised": All the lenses are optimised in some way, even the corrected curve ones. "Optimised" means nothing.
FreeForm = CNC machined. You can cut a spherical surface on a CNC generator and call it FreeForm(and if it is a corrected curve sphere you can slap "optimised" on it as well
).
<rambling mode = off>
Best regards,
Nikolay Angelov
I Agree with Nikolay's post. This is all new technology and the semantics at present are confusing at best. "freeform" surfacing allows the labs to basically place aspheric and complex curves on the back of the lens. The term digital is very ambiguous. If I use a CNC generator to put a spherical curve on the back of a lens is that not digital by virtue of CNC ?? I believe the optical industry is in the process of a much need technological catch up phase. Digital is a term the public loves to hear but really means very little in my view.
Last edited by RIMLESS; 11-27-2011 at 10:41 AM.
However simplistic it may be, I tell my accounts that digital is a process and free form is a design. All free-form lenses are produced digitally, but not all digitally produced lenses are free-form.
I'm nor sure why you intuit that FF FT's would provide inferior vison, simply because of the near vergence/base curve issue. All Best form issues are about FOV, not axial vision. Reading tasks are inherently smaller FOV. My experience with FF FT is that all cyl over 1 D have clients remarking how much sharper they are.The RX is indeed the corner stone of good vision.
However i suspect that the the described "Digital Bifocals" provide worse vision than conventional bifocals in the near zone.
We know (and can calculate) the exact performance of conventional bifocals:
http://books.google.bg/books?id=Zl45...page&q&f=false
I haven't seen any data on those newly "optimised" lenses, to show they aren't inferior.
<rambling mode = on>
"Digital" is meaningless term, every lens design have a "digital" step where the surface is calculated.
Same with "optimised": All the lenses are optimised in some way, even the corrected curve ones. "Optimised" means nothing.
FreeForm = CNC machined. You can cut a spherical surface on a CNC generator and call it FreeForm
<rambling mode = off>
Best regards,
Nikolay Angelov
Go Figure.
B
What % increase over your conventional FT28 price? I will post the question in the Professional forum as we don;t talk prices on here.
When you use "FF single vision software", you select a spherical blank with a desired base curve.why you intuit that FF FT's would provide inferior vison
The software calculates a aspheric back surface with properly selected level of asphericity, to acheave the design target (reduce oblique astigmatic and power error etc.)
Analogues to having a lens with aspheric front surface and a spherical back.
With conventional aspherical blanks, you have a small step base curve system becouse the amount of asphericity is different for each base curve/power range.
Choice Of aspheric base curve:
http://books.google.com/books?id=Zl4... small&f=false
http://books.google.com/books?id=Zl4... small&f=false
Thus i assume different levels of asphericity will be required for the 2 different front curves of the bifocal.
The SV software will optimise the asphericity for the far power/front curve, you will get an improved far portion.
The same asphericity will be inappropriate for the near portion front curve, AFAIK this will increase errors (oblique power error, astigmatism etc.).
PS: We are yet again guessing the technical characteristics of a simple optical lens ... where are the technical specifications, comparison ray traces etc. Is opticianry turning into astrology... fairy tales with no scientific basis.
If the human eye was a precise lens analyzer, I *might* be inclined to agree with you. But...it is not, and you can ray trace all you want, but *wearers* of ophthalmic lenses are NOt sensitive to the degree you infer about the incorrect optomization. They are, however sensitive to changes in many other aspects, such as geometric distortion, which is tolerated by ophthalmic lens optimzers/deigners, and any changes in this regard humans ARE sensitive to.When you use "FF single vision software", you select a spherical blank with a desired base curve.
The software calculates a aspheric back surface with properly selected level of asphericity, to acheave the design target (reduce oblique astigmatic and power error etc.)
Analogues to having a lens with aspheric front surface and a spherical back.
With conventional aspherical blanks, you have a small step base curve system becouse the amount of asphericity is different for each base curve/power range.
Choice Of aspheric base curve:
http://books.google.com/books?id=Zl4... small&f=false
http://books.google.com/books?id=Zl4... small&f=false
Thus i assume different levels of asphericity will be required for the 2 different front curves of the bifocal.
The SV software will optimise the asphericity for the far power/front curve, you will get an improved far portion.
The same asphericity will be inappropriate for the near portion front curve, AFAIK this will increase errors (oblique power error, astigmatism etc.).
PS: We are yet again guessing the technical characteristics of a simple optical lens ... where are the technical specifications, comparison ray traces etc. Is opticianry turning into astrology
FWIW. Yes, I'm into astronomy (not astrology). TOO TOO much focus the perfection of optics. They're humans we're fitting, you know. And their vision is fluid. And exams are done under non-representative samplings of the human eye's optical train, i.e., pupils are too big in the exam room.
My advice; Don't sweat this small stuff.
B
We are comparing the merits of 2 lenses, products we sell.
What are the differences, is one better and so on (as we are paid to know).
What does the eye's imperfections have to do with comparing 2 products?!
It's like saying that we can't compare 2 types of car tyres because the roads are not perfect and change with time.
What i am trying to express in more general terms is this:
Lent manufacturers keep talking about "new lens grinding technology", "new lens design", "new polishing system".
I don't care one bit how they make the lens.
None. Zilch. Nada.
Customers care even less (if that's possible).
What I do Care about, is what the actual optical effect of the lens is.
This information allows me as a professional to decide what lens to use and recommend i.e. to do my job better.
I know the tools/lenses i use today. How they work, what are their pluses and minuses.
Then a manufacturer comes with the new "lens of the day".
They go on and on about how they make it (like it matters to me).
And they never say:
- Here is a ray race of an old lens and our "new lens".
- We managed to improve (reduce) skew distortion by "n"%.
- Oblique astigmatic error is guaranteed below "n" in this zone.
- Oblique power error is guaranteed below "n" in this zone.
- It has improved fitting error tolerance, keeping aberrations "a" and "b" below value "n" with fitting error of "z"mm.
- ...
And if they state some benefits of the "new lens" it is never quantitative. It has "wider channel", "smooth transition", "bigger zones" etc.
I don't care about abstract "perfection of optics".
I want to know the actual differences between the products i offer, if there is any.
That way i can choose a suitable product and do my job better.
At the moment we have clearly defined and well understood lenses. They are explained in detaile in professional textbooks.
Why should we expect any less from the new lenses which are supposed to be better.
PS: I love the nitty gritty manufacturing stuff, but while interesting it is no substitute for lens specifications (i.e. what does the lens do quantitatively) and documentation.
Best regards,
Nikolay Angelov
Last edited by Nikolay Angelov; 11-28-2011 at 06:53 PM. Reason: typo :)
Nikolay, I only wish the human eye and vision system was such a reliable, consistent and impartial analyzer of the optical specs you're after. Unfortunately, it is not. And that's why fitting lenses to humans will remain part art.
B
Bingo! Never fall to marketing jargon.
There are currently 1 users browsing this thread. (0 members and 1 guests)
Posting Permissions
Reply With Quote
Bookmarks