Question for Darryl on progressive design

[Judy Canty]

Snark? Really? That's hardly the case and I didn't realize I needed 'special' opinion to chime in. And for the record, I am both an industry professional and acknowedged expert.

My post wasn't meant to ruffle feathers or advocate a specific brand or supplier, but rather to state an obvious fact that the mass influx of confusion and self claim marketing propaganda is caused by 'ALL' of the manufacturers. Actually, I admire Darryl's intelligent posts and views on specific topics.

On the other side of the same coin, I can also say that most companies have excellent products and do thier due diligence with clinical trials prior to launching to ECP's. However, they have all created this monster to try and put space between them and their competitors and its time they should all band together and use common marketing jargon.

That's all I meant, so please consider this an apology and lighten up.

Really. My opinion.

[Wes]

All this tiff aside, hindsight does have a good point in that the industry needs to standardize the terminology regarding newer lens technologies. Freeform, digital, customized, optimized, blah blah. These words mean too many different things depending on who's staying them. Determining if a lens is free-formed from a puck or if it's just molded from a digital design with traditional surfacing, or if it's free-form back surfaced, or partially back surfaced, or or or.. my head wants to explode.

[Darryl Meister]

These words mean too many different things depending on who's staying them. Determining if a lens is free-formed from a puck or if it's just molded from a digital design with traditional surfacing, or if it's free-form back surfaced, or partially back surfaced, or or or.. my head wants to explode

Honestly, one of the main reasons that I now avoid the Progressive Lens Forum is because so many opticians have become so "disinformed" by certain companies exploiting this confusion that the number of grossly inaccurate generalizations made in this forum has become too frustrating.

Best regards,
Darryl

[HindSight2020]

All this tiff aside, hindsight does have a good point in that the industry needs to standardize the terminology regarding newer lens technologies. Freeform, digital, customized, optimized, blah blah. These words mean too many different things depending on who's staying them. Determining if a lens is free-formed from a puck or if it's just molded from a digital design with traditional surfacing, or if it's free-form back surfaced, or partially back surfaced, or or or.. my head wants to explode.

Exactly my point. Lets not forget bi-aspheric, 3D abberation filter, advanced digital, customized, personalized, individualized, blah blah blah.

I do this presentation frequently to OD's and OA's up here and break the process into 'design' and 'processing'. Everyone always appreciates a presentation that is true and based on facts. Heck I usually get a handshake and new business from them based on honestly alone.

[Jason H]

Ok, you have an empty room and a bag full of leaves. Dump the leaves into the room and push them around. Such is the dilemma of progressive lens engineers. Where do you put them? How high the piles? I use this example to help consumers understand what they are up against. Stronger rx= more leaves. Got to keep esoteric ideas accessible for everyday people. Would love to hear a better idea if you have one.

[sharpstick777]

There was nothing wrong with hindsight's post. He has just as much right to express his opinion as Darryl.

Whether hindsight meant it or not, his "tone" came across a little harsh to both me and Judy. Tone is tough to manage online, but I understand why Judy felt it was more of a dig than anything else.

[sharpstick777]

Darryl,
I argue with you more than anyone, but I still greatly respect your amazing knowledge, your contributions to this forum, and your lack of bias. I am a better Optician because you are here, and I know I owe you a lot of thanks.

So thanks, for more contributions to our knowledge and education over the years than I can count.

Sharpstick

Sorry that I'm late to this conversation, but I rarely check the posts in the Progressive Lens Forum, which I'm afraid frequently caters to brand-specific marketing propaganda precipitated by a great deal of personal bias, rather than objective fact. However, there have been a lot of very good posts already. That said...

The fact is, advanced or absolute presbyopes face a paradox with progressive lenses: A shorter corridor length allows the wearer to more easily reach the full add power necessary for comfortable near vision and provides a wider field of reading utility for a given distance from the fitting point, whereas a longer corridor length provides more intermediate utility and lower levels of peripheral distortion, which become particularly important as the add power increases (due to the absence of adequate accommodative amplitude for mid-range viewing distances and to the fact that peripheral distortion is proportional to add power).

This is, in fact, why there are actually two diametrically opposed philosophies used by lens designers when designing "multi-design" progressive lenses that vary by add power: The first philosophy seeks to make the design harder as a function of add power in order to provide a shorter corridor with a larger zone of stabilized add power, whereas the second philosophy seeks to make the design softer in order to provide a longer corridor with more intermediate utility and less peripheral distortion.

As to which design philosophy is better is primarily a matter of personal preference for the wearer, based upon his or her specific visual requirements, previous lens design, et cetera. Otherwise, a strong argument can be made for either philosophy or even not varying the corridor length as a function of add power at all.

Best regards,
Darryl

[HindSight2020]

Whether hindsight meant it or not, his "tone" came across a little harsh to both me and Judy. Tone is tough to manage online, but I understand why Judy felt it was more of a dig than anything else.

Again, for the record - no dig, tone, foulness or harshness implied. Some people need not to take things so seriously. This is a forum where we post opinions. Whether you agree with the opinions or not is irrelevant.

A forum where everybody group hugged and agreed all day long wouldn't be fun or interesting.

[Darryl Meister]

So thanks, for more contributions to our knowledge and education over the years than I can count.

I certainly appreciate the positive feedback.

Again, for the record - no dig, tone, foulness or harshness implied.

Okay, I think we can all agree: "No harm, no foul." So let's all get this thread back on topic.

Best regards,
Darryl

[sharpstick777]

I certainly appreciate the positive feedback.

I think one of the best ways to understand this subject is to understand the difference between hard and soft lens designs first, then from there we can understand how making the corridor shorter, the add stronger, or the reading wider, as the same effect as making a lens "harder". ie, increases what I call Total Potential Distortion.

I will see if I can put together some drawings, curves work well for demonstrating this.

[Darryl Meister]

I think one of the best ways to understand this subject is to understand the difference between hard and soft lens designs first... I will see if I can put together some drawings

There is actually a pretty lengthy presentation on this topic in the article on OptiCampus.com that was referenced earlier: Distribution of Surface Optics.

Best regards,
Darryl

[sharpstick777]

Darryl, I understand your frustration, but won't your absense only make the matter worse, not better?

Honestly, one of the main reasons that I now avoid the Progressive Lens Forum is because so many opticians have become so "disinformed" by certain companies exploiting this confusion that the number of grossly inaccurate generalizations made in this forum has become too frustrating.

Best regards,
Darryl

[sharpstick777]

The other factor that frustrates me is that most progressives, even in free-form are "adaptive", which means the design changes as the add increases. Although this is generally good, NO company (even Zeiss) tells you HOW their lenses change. Some narrower the corridor, some raise the distortion, some get harder, some a combination of all these.

It means we are Beta testing these features on our patients. Grre.

[Darryl Meister]

Although this is generally good, NO company (even Zeiss) tells you HOW their lenses change. Some narrower the corridor, some raise the distortion, some get harder, some a combination of all these

Actually, Carl Zeiss Vision does provide these technical details for products in which there is a specific variation in the distribution of progressive optics as a function of add power associated with a lens design feature. See, for instance, the SOLA Elan White Paper for a detailed technical discussion of the "design by add power" and "design by base curve" features of one recent CZV progressive lens.

For ZEISS brand progressive lenses, there is no specific adjustment made to the corridor length as a function of add power, although the inset of the corridor and near zone are modified accordingly, as described in the technical documentation. Otherwise, the lens designers fine-tune as needed the lens design associated with each add power to provide a consistent distribution of progressive optics over the range of add powers.

Best regards,
Darryl

[sharpstick777]

Actually, Carl Zeiss Vision does provide these technical details for products in which there is a specific variation in the distribution of progressive optics as a function of add power associated with a lens design feature. See, for instance, the SOLA Elan White Paper for a detailed technical discussion of the "design by add power" and "design by base curve" features of one recent CZV progressive lens.

Great! But I have never heard of the Elan, and its seems a European only lens, is there anything similar for the new Choice Series? There were very vague in NYC when I asked that question, I think their eyes rolled around a few times.

PS Darryl, there is another thread on the Choice Series in the general forum, with other questions.

[Darryl Meister]

is there anything similar for the new Choice Series?

Choice is a ZEISS brand product, so:

For ZEISS brand progressive lenses, there is no specific adjustment made to the corridor length as a function of add power, although the inset of the corridor and near zone are modified accordingly, as described in the technical documentation. Otherwise, the lens designers fine-tune as needed the lens design associated with each add power to provide a consistent distribution of progressive optics over the range of add powers.

Best regards,
Darryl