Freeform / Digitally Surfaced Lenses

[whitneyd74]

I'm not sure if I should post this here or in the PAL discussion section, so I apologize if this is in the incorrect place. I know that the sales reps all say that digitally surfaced/freeform lenses work for any PAL wearer, but I'm trying to narrow that down a bit. What are the Rx parameters that you go by when determining whether or not a patient should be in a "traditional" PAL or a digitally surfaced PAL? I have heard to use it for complex Rx's - if that is true, what constitutes a complex Rx? Can you tell that I'm confused? :(

-Whitney

[Barry Santini]

I believe that one should select the appropriate FF/personalized progressive in almost all cases, compared with traditional porgressives.

Power accuracy alone makes FF the preferred choice for me.

Barry

[drk]

Seriously, I was going to start this thread this a.m.

Here's what I think I know:

Biometric:
Unusually long vertex distance (deep set eyes)
Unusually large or small p.d.

Frame-related:
Lots of facial wrap
Very long or very short fitting heights

Ametropia-related:
Astigmatism of 2D x90 or x180 +/- 20 degrees
Oblique astigmatism of 1-1.50 D
Anisometropia
Probably full add powers


Here's what I don't know, and maybe someone else does:

There is one optimal base curve per lens power, but as one approaches the extremes of the range of powers cut on any given base, the peformance drops off. How do we know that?

There may well be "the flattest" or "the steepest" base curve in a lens series, and all powers greater will be cut on that base by necessity. So I'm guessing that very high minus and plus would be a candidate.

[HarryChiling]

Here's what I don't know, and maybe someone else does:

There is one optimal base curve per lens power, but as one approaches the extremes of the range of powers cut on any given base, the peformance drops off. How do we know that?

I've been curious about this myself. If you have a copy of their recommended powers chart for the lens series then you would just use the Rx in the middle and it should be fairly accurate that way, as it moves away from that optimal curve then more aberrations are present and the Rx's that are on the extreme ends of the base curve selection chart are going to have the most amount of aberrations. Now the big question is: Since the designer has a set thresh hold for a certain aberration they are trying to control, what is it for that lens series?

One lens designer focuses on RMS, so this is going to meet the designers objective the best on the optimal power and curve combination, right now we don't know the designers objective or the thresh hold for the amount of error allowed in that series. To me it almost feels like an artificially created need for FF in a sense. Progressives from the start could have been manufactured for a higher cost with traditional technologies to higher tolerances we could just never justify the cost.

[drk]

That's an interesting point: Let's say Essilor doubled the base curve offerings--we'd have better performance spheres.

Cylinders would still be a problem, though, and I guess at some point they just said "good enough".

The nice white paper I cited has a chart that shows in rather great detail how the aberrations build off "the sweet spot" (to use a Santini-ism), and with increasing cylinder. The chart doesn't place a numerical value on the aberrations, just a color temperature, but I'm guessing it's in 1/4 D steps.

[bob_f_aboc]

So as more manufacturers move to free-form/digital technology, shouldn't they begin offering more base curves in their single vision product? I would think that since they aren't making all of the right/left/base/add combos they would be able to offer SV lens blanks in .50 or even .25 steps and still be able to make more money.

I'm only guessing, but I hope that its cheaper to make a spherical SV mold than it is to make a PAL front mold.

My 2 cents.

[Jacqui]

So as more manufacturers move to free-form/digital technology, shouldn't they begin offering more base curves in their single vision product? I would think that since they aren't making all of the right/left/base/add combos they would be able to offer SV lens blanks in .50 or even .25 steps and still be able to make more money.

I'm only guessing, but I hope that its cheaper to make a spherical SV mold than it is to make a PAL front mold.

My 2 cents.

Some do offer at least basic materials in 1.00 diopter steps.

[Barry Santini]

One lens designer focuses on RMS, so this is going to meet the designers objective the best on the optimal power and curve combination, right now we don't know the designers objective or the thresh hold for the amount of error allowed in that series. To me it almost feels like an artificially created need for FF in a sense. Progressives from the start could have been manufactured for a higher cost with traditional technologies to higher tolerances we could just never justify the cost.

Harry,

Better selection of base curves would improve the performance of traditional designs, but at increased cost (is that what you are saying?). Maybe equal to the FFs, such as Element. Just my speculation...

Barry

[DoubleD]

While I fully support the accuracy attainable with FF, it will be difficult to really prove final result is best at patient level IN MOST CASES.
1) How many of us really know how a base curve versus lens power reference is REALLY determined? Even for spherical single vision!
2) To really get eyewear technically correct, a dispensing optician would need to assess much more than Rx, PD, VD, wrap, panto. Skimping on just this data throws a curveball into the old lens design theory in even the FF designs.
Yes, we can make lenses better/ more accuarate. I wish we could fit glasses as well.

[Mike Fretto]

2) To really get eyewear technically correct, a dispensing optician would need to assess much more than Rx, PD, VD, wrap, panto. Skimping on just this data throws a curveball into the old lens design theory in even the FF designs.
Yes, we can make lenses better/ more accuarate. I wish we could fit glasses as well.

Isnt this one of the really big advantages to FF, taking into consideration the frame dimensions as well as RX gives the patient a lens designed specifically for their situation. I have worked with far too many people who measure for height without properly adjusting the frame before measuring or they are sitting a foot lower than the patient:drop:

[Robert Martellaro]

That's an interesting point: Let's say Essilor doubled the base curve offerings--we'd have better performance spheres.

I think it was Shamir that had to wait until the SV lens manufacturers could supply closely spaced BCs on their spheric blanks before they could introduce their free-form products in Trivex.

FYI, Zeiss and Hoya have diopter or less spacing between BCs for most of their semi-finished product lines.

The chart doesn't place a numerical value on the aberrations, just a color temperature, but I'm guessing it's in 1/4 D steps.

Probably closer to an eighth.

Seriously, I was going to start this thread this a.m.

Here's what I think I know:

Biometric:
Unusually long vertex distance (deep set eyes)
Unusually large or small p.d.

Position of wear optimization required for vertex. Some designs have variable insets keyed to the PD, many are by prescription only (for moderate to high plus and minus), the latter standard fare with premium semi-finshed PALs, albeit with slightly less precision.

Frame-related:
Lots of facial wrap

For those designs that are optimized for POW.

Very long or very short fitting heights

I'm not sure what free-form brings to the table here that's not available with traditionally ground PALs.

Ametropia-related:
Astigmatism of 2D x90 or x180 +/- 20 degrees

When I was using the Multigressiv, Rodenstock considered 3.00 DC as the breakpoint. I start twisting arms above 2.50 DC, slightly less for oblique axes.

Anisometropia

It would be nice to eliminate imbalance on the distance and/or near gaze, although none presently can, that I know of. There's potential for improved binocular vision if the Rx is optimized in real time, and the software addresses the problems with the unequal prism and magnification off-axis with these Rxs.

Probably full add powers

Lenses that have insets determined by power and PD will have a slight advantage here, especially with narrow or wide PDs as you noted above.

Some lenses can do all of the above, some less (sometimes much less), and some are capable of additional customization. It's important to know what each design is capable of; high cyls get atorics, -10.00 Add 2.75 PD 56 needs a custom inset, and so on.

[drk]

Martellaro, you're one smart dude.

Also, the lens optimization per seg height/frame makes sense to me. Sure, we can use the short designs already or Definity or Gradal for the big frames, but it sure would be nice to not have to think that through.

[Eyeguy842]

Hi all
I'm new on this board but have 30+ years optical experience, mostly retail side but now in wholesale lab enviornment. I have put quite a few folks in FF lenses both SV and PALs. Not a single one has not raved about the lens technology on follow up. I myself have worn most of the PALs on the market over the past 15 years with fair to good success. Knowing all of the tech stuff I was not prepared for the feeling that I was wearing SV again but could see intermed. and near with virtually no swim.
-2.50-0.75x55
-2.25-0.50x108
+2.75 OU
I can't think of a single application that FFs would not be my first choice, without any thought. Except wraps.
I'm trying to come up with the best lens that already incorperates the theory of the Rx compenpsator, which is a useful tool, but truely in the lens design itself. FF is the technology that will give us that but base curves are an issue, or more accurately, the lens designer's perception of base curve availibilty is the issue.
I agree with the post about the "alleged" opticians that don't preadjust. Where is our industry headed when all of us old farts are gone and we've only trained button pushers? But I digress, any good options on wraps?

[Barry Santini]

I like the following for moderate Rx & up wraps:

Shamir Attitude, SV & Prog.
KBCo Wrap Solutions

I know Rodenstock is releasing this year amn optimized, FF SV wrap lens.

I'm sure others will as well.

I don't think wrap Technology will really reach it pinnacle until its two-side surfaced, Ala Hoya ID

Barry

[Eyeguy842]

Thanks Barry
I've used all of the above with mix'd results in wraps. But they are all just asph. 8 base blanks. I'm looking for a new technology or a different use of a new technology. Maybe I can get our engineers to agree.
I like your choice of the Hoya ID.
Have you tried the:
Hoyalux Lifestyle ID-transition, clr, short corr., poly(really not bad)?
Also the SV NuluxEP.

Jerry Shelton
HOYA America
Dallas, TX

[Barry Santini]

I Love Hoya ID! And my clients who will pay for it do too!

I didn't like my set of Nulux EP. I can't figure out why they were not what I expected.

Barry

[Barry Santini]

Correction:

Shamir *autograph* (FF) attitude.

Barry

[Eyeguy842]

That explains the disappointment. You have my cell, call me about the EP. Who is you rep?

[drk]

Eyeguy/Hoya rep:

You mention "low swim" which means low amounts of unwanted astigmatism in the near zone periphery, yet you have a 2.75 power change in your lens.

To what, specifically, do you attribute the reduction in near-zone peripheral astigmatism?

[Eyeguy842]

Hi doc
Sorry it's taken me a while to get back to your question. First off I am not a sales rep. I am simply a individual that has a passion for all thing optical and, like you, ask questions to aquire information and different perspectives so that I can form a more educated understanding and
opinion. That being said, my understanding is that by putting the vertical component on the front surface helps reduce or minimize vertical eye movement. More importantly for me being myopic the horizontal component is placed on the back surface of the lens. This brings the distortion closer to my eyes creating a less minus (or more plus) situation. Which is peculiar to me because us myopes are a strange lot. You can over correct the heck out of us, but don't take any power away. I don't know if it is actually decreasing my VA in that area of the lens so I don't "see" the distortion or if the distorted areas are eliminated. Hummm. How, I wonder, does that effect a presbiopic hyperope? Over minus under plus. Any thoughts?
A curious optician/optometrist wannabe.
Jerry

[PKCRM114]

i have a question about the description of the hoya id's front vertical component reducing "vertical eye movement" doesn't that just mean shortening the perceived corridor? is that really a benefit or just an effect?

[Eyeguy842]

It does in effect shorten the progressive corridor which helps reduce the eye rotation and allows for a faster and smoother transition from distant to imtermediate to near. The horizontial being on the back surface creates a wider distortion free visual field. By having two seperate surfaces to work with each can be specifically calculated for the Rx. The re-intergartion of the two surfaces gives you a wide field of view at all distances that is virtually "swim free". It really works great.

[Bill West]

Definition FF= Free form

My definition: FF= Free Fall

I am seeing people almost every day who have had free form lenses and the outrageous cost thrown at them and they are not happy.
Like the lady on medicare who came in the other day and showed me her last visit to her OD, who recently built an 800k house and whose help can't even fill out an rx correctly. I have to call for axis, add or something all the time.
His charges: Comp exam $176 refraction $35 Fundus photo $30

Metal frame $152 Right lens $175 Left lens $175 AR $ 115 Transitions $178
You do the math.
I'm just going to keep advertising prices people can afford. This business is headed for the same place nearly every other business in this country is at now. Priced out of the market, operating on borrowed money, broke, looking for some way out ie. GM, Ford,Chrysler, your bank,and way too many business to list.
So good luck, I don't really believe in "good or bad luck", to all you hi-tech optical people who want to impress "your doc" with the sale of high ticket items. I'll see you on the way down, I'm going the other way.:cheers:

[Jacqui]

I'm just going to keep advertising prices people can afford. This business is headed for the same place nearly every other business in this country is at now. Priced out of the market, operating on borrowed money, broke, looking for some way out ie. GM, Ford,Chrysler, your bank,and way too many business to list.
So good luck, I don't really believe in "good or bad luck", to all you hi-tech optical people who want to impress "your doc" with the sale of high ticket items. I'll see you on the way down, I'm going the other way.:cheers:

Good for you !! I'll be there to keep you company. :D

[Eyeguy842]

Good Morning Bill and Jacqui
After reading your post I intentionally waited a couple of days so that I could reply professionally and with the least amount of sarcasim.
Point 1)
In the 30+ years that I have been an optician, I have always considered it to be my primary responsiblity to educate my pts/customers, to the best of their understanding, of what is currently available and to make my professional recomendation based on their Rx and their expectations. With that, the pt/customer is better equiped to make an educated decision for themselves. I don't prejudge or prequalify people and decide who gets the flat top and who gets the progressive.
Point 2)
Addressing your statement "hi-tech optical people who want to impress "your doc" with the sale of high ticket items", in my humble opion, those "optical people" are certainly not opticians but sales people that happen to be in the optical business and probably don't care about their pt/customer or haven't been properly taught.
Maybe it isn't a fair inditment of a significant step forward in our industry simply out of your perceived angry with the current economical situation and that dr's 800k home.
Thank you for allowing me to express myself and for taking the time to read this as I know that you must have cylinder bowls to clean and need to change the kryptoc oil.
Jerry