Corridor length change in free-forms

[rdcoach5]

If I fit a Patient with one of the new smaller B-dimension frames, I have found the Kodak Unique adapts to the smaller fitting height. What happens to the corridor if I fit a free-form to a B-dimension of 46 or more? Do we now have a long corridor free-form ? Is there a limit? Do we get more side distortion ?
Bob Taylor

[Robert Martellaro]

If I fit a Patient with one of the new smaller B-dimension frames, I have found the Kodak Unique adapts to the smaller fitting height. What happens to the corridor if I fit a free-form to a B-dimension of 46 or more? Do we now have a long corridor free-form ? Is there a limit? Do we get more side distortion ?
Bob Taylor

Bob,

The Unique uses a corridor length based on the seg height. Other companies like Zeiss have two lengths, which gives us the freedom to match the corridor length to the needs of the wearer, regardless of the seg height or B measurement.

Off-axis blur with the short designs will vary depending on the lens design. Short corridors will usually have more blur in the distance periphery and will feel more dynamic, although our brain handles this quite well.

[rdcoach5]

Bob,

The Unique uses a corridor length based on the seg height. Other companies like Zeiss have two lengths, which gives us the freedom to match the corridor length to the needs of the wearer, regardless of the seg height or B measurement.

Off-axis blur with the short designs will vary depending on the lens design. Short corridors will usually have more blur in the distance periphery and will feel more dynamic, although our brain handles this quite well.

Robert
Thanks, so if I have someone on computers all day and I fit them in a big frame with a 30 or more seg, the Unique will give them a huge and very gradual corridor. I'll let you know if it works
Bob Taylor

[Robert Martellaro]

Robert
Thanks, so if I have someone on computers all day and I fit them in a big frame with a 30 or more seg, the Unique will give them a huge and very gradual corridor. I'll let you know if it works
Bob Taylor

Bob,

I talked to Chris at Signet Armorlite this morning. He said their software determines the length, and that the transition from a short to medium length corridor (probably along the lines of the Concise and Precise designs) is about 17mm to 18mm, although the shape of the frame and inset could vary this to some degree. I wasn't able to get a definitive answer as to the degree of optimization for the inset (for wide/narrow PDs and distance Rx), although the lens is atoric. It is not optimized for position of wear and uses standard front curves (not flatter/aspheric). They are open to my suggestion of opticians being able to specify the corridor length, and they are looking into the feasibility of using front aspheric curves.

The Unique comes in the widest range of materials (including a polarized cr39) of any free-form/direct to surface lens that I'm aware of, and is the only one available in Trivex, although that's about to change at Hoya. I feel that this is a good lens, and would be a very good lens if the front curves were flatter, and if the AR coat was a notch slicker and scratch resistant, along the lines of Hoya's Super Hivison and Essilor's Alize. That said, the Unique is priced lower than other lenses in its class, which makes this a very competitive design/product indeed.

Regards,

[rdcoach5]

Bob,

I talked to Chris at Signet Armorlite this morning. He said their software determines the length, and that the transition from a short to medium length corridor (probably along the lines of the Concise and Precise designs) is about 17mm to 18mm, although the shape of the frame and inset could vary this to some degree. I wasn't able to get a definitive answer as to the degree of optimization for the inset (for wide/narrow PDs and distance Rx), although the lens is atoric. It is not optimized for position of wear and uses standard front curves (not flatter/aspheric). They are open to my suggestion of opticians being able to specify the corridor length, and they are looking into the feasibility of using front aspheric curves.

The Unique comes in the widest range of materials (including a polarized cr39) of any free-form/direct to surface lens that I'm aware of, and is the only one available in Trivex, although that's about to change at Hoya. I feel that this is a good lens, and would be a very good lens if the front curves were flatter, and if the AR coat was a notch slicker and scratch resistant, along the lines of Hoya's Super Hivison and Essilor's Alize. That said, the Unique is priced lower than other lenses in its class, which makes this a very competitive design/product indeed.

Regards,

Robert, Yes we have dispensed a ton of Kodak Unique lenses the past few months because of their promotion pricing. My Essilor rep even called to ask what happened to our Physio drop-off in usage. I hope Signet keeps this pricing and improves the brittleness of their hi-index Instashades.Poly is the only Instashades I would recommend in rimless. Our customers have been very pleased with the Unique. We,ve gotten some" WOWS " from it
Bob Taylor

[Robert Martellaro]

Bob,

It's still very competive at the regular prices.

Keep in mind that the Physio 360 is not atoric, and might not be the best choice for your high cyl Rxs. (The Unique is atoric.) The 360 uses other methods to and increase visual comfort.

Regards,

[drk]

Physio 360 isn't atoric?

Man, I'm getting confused.

[Robert Martellaro]

Physio 360 isn't atoric?

Man, I'm getting confused.

You, me, and the rest of the ophthalmic community. I'm reasonably sure that Rodenstock, Signet Armorlite, Shamir, Essilor (Ipseo only), Seiko, and Hoya incorporate an atoroidal surface in their designs. However, that's only one of many optical tweaks available to the lens designer when using free-form, and trying to determine which design will benefit the specific individual/Rx tends to be as clear as mud, and will remain so until the manufacturers give us more info regarding which optimizations are incorporated in their designs. My goal is to get this information, try the lenses in my own Rx (an expensive proposition), and share this information with anyone willing to listen.

Regards,

[HarryChiling]

What happens to the corridor if I fit a free-form to a B-dimension of 46 or more? Do we now have a long corridor free-form ? Is there a limit? Do we get more side distortion ?

The corridor can be varied to whatever a designer wants the corridor to be, I am sure that their are free form designs with longer corridors than others, but long corridor is a vague term, yes there is a limit if the corridor is too long the angle the patient views through the lens can become so great that the eye would strain to get into the reading or potetially even get total internal reflection if the situation were right.

[AWTECH]

Robert Martellaro said:

Quote:
Originally Posted by drk
Physio 360 isn't atoric?

Man, I'm getting confused.

You, me, and the rest of the ophthalmic community.

The difficulty many are having in this tread and others related to freeform is the result of trying to apply traditional terms to new method of lens manufacturing.

Remember, what matters is not what industry buzz word that is attached to a lens design but how the actual prescription on the patient performs.

A great freeform design allows the designer to manage light travel across the lens with minimal abberations.

This produces an aspheric lens surface. By aspheric I mean non-spherical.

Traditional PAL lenses are limited by the combination of spherical and cylinder cuts made to the back of a fixed PAL design.

Designing lenses is not something that every optician is going beable to do. Dispensing lenses is one key facet for the Optician to perform, and with good freeform lens designs the Optician should beable to supply the frame and patient information such as Rx and OC height, PD and the company producing the freeform lenses should be able to make a proper lens for the patient.

[HarryChiling]

If you want to apply a term to the surface, try deformed conic. I think that this describes the free form surfaces better than any traditional term.