PAL Corridors

[2020texan]

Excuse the elementary question. If I don't ask I don't know right and I'm a self motivated Optician to learn all I can in this career.

Do the lengths of the what I call corridor of Progressives change depending on the B measurement of the frame?

I had a lady that wanted a really big and deep frame this time. She liked a Ray Ban...RB7066 in eye 54 withB measure 44.2 I used a Varilux Comfort 2 Drx. At dispense the distance was fine but reading and intermediate she wasn't happy with. If she lifted the frame up and looked in the very bottom it was okbut just normal posture that wasn't going to work without holding theframe. Seg ht used was a 30.

She wanted to try PALs again as she's never been able to wear them without issues (and she could bejust one of those people who will never be able to adapt to them)She's even had smaller frames that weren't as deep and still had problems finding her reading areas. She was determined on getting a deeper frame this time.

After thinking or overthinking about it maybe, after I while I was curious how the PAL was going to bepositioned in such a deep frame, her eyes were more towards the topof the frame. I even asked my coworker about it and he seemed tothink it would be fine. And then come dispense day she's lifting the frame.

So does PAL length change according to depth of frameor all PAL corridor lengths in a way stationary they just shift according to seg where they'll be positioned. Hopefully I'm conveyingmy question the way I see it in my head lol Thanks!

[Hayde]

Howdy, Tex!

Ten years ago the answer to your question was categorically 'no.' PAL dimensions were static and your frame had to have room for whichever one you picked. Many of these conventional PALs are still on the market.

However, you can probably access a number of "free form" PALs now which permit much more customization. Such a PAL identified as a "variable fit" will take into account the seg height you input and distribute the add progression accordingly.

That sounds like a tough patient, and no multifocal will magically let her see every range at every desired angle. Unless she accepts that reality, I think she may be better off with multiple single-vision pairs--especially if you're still mastering PAL dispensing.

Welcome to Optiboard! I hope you'll have some fun with the search feature and find some great reading suggestions. (Some of the book may seem pricey, but they're well worth it!) Some great articles on Progressive Lenses by Darryl Meister are floating out there too. Those will give you a good primer on how different older PALs work, and your lens reps will be happy to preach the virtues of recent models.

[bretk0923]

Not an elementary question at all. Like you say, if you don't ask, you won't know.

In the example you provide, Varilux Comfort 2 DRx is what's known as a variable-length progressive. And in this case, you are correct that the corridor length is dependent on the B-size of the frame, to a certain extent. There are some limitations to how long the corridor will actually be, but the underlying point is that with variable-length progressives you will not be able to control the position of the reading area.

You'll likely get plenty of recommendations for different progressives to use in this situation from different OptiBoarders, but it is most definitely good practice to be cognizant of the frame's B-size and how that relates to the desired progressive corridor. For more information, there is a CE course from 2020 Magazine that explains this quite well - https://www.2020mag.com/ce/coping-with-corridors-89259.

[DanLiv]

Hayde is totally right. For your particular situation, the DRx lens you selected is NOT a variable corridor, so it will have a fixed length like traditional PALs (comes in standard and short corridor). This sounds like an old fashioned troubleshoot: add too weak, seg too low, or maybe she just doesn't like dropping gaze enough to utilize standard corridors and you could put her in a short corridor.

[Hayde]

Not an elementary question at all. Like you say, if you don't ask, you won't know.

In the example you provide, Varilux Comfort 2 DRx is what's known as a variable-length progressive. And in this case, you are correct that the corridor length is dependent on the B-size of the frame, to a certain extent. There are some limitations to how long the corridor will actually be, but the underlying point is that with variable-length progressives you will not be able to control the position of the reading area.

You'll likely get plenty of recommendations for different progressives to use in this situation from different OptiBoarders, but it is most definitely good practice to be cognizant of the frame's B-size and how that relates to the desired progressive corridor. For more information, there is a CE course from 2020 Magazine that explains this quite well - https://www.2020mag.com/ce/coping-with-corridors-89259.

Bretk, I have a hard time keeping my Comforts straight. Isn't DRx just a digital mold of the old Comfort 2 and the new new "Comfort W2" the variable fit?

[Tallboy]

Bretk, I have a hard time keeping my Comforts straight. Isn't DRx just a digital mold of the old Comfort 2 and the new new "Comfort W2" the variable fit?

The DRX is a Full backside production of the Comfort 2 design, and the W2 is as you described

[Hayde]

The DRX is a Full backside production of the Comfort 2 design, and the W2 is as you described

Thanks TB,

I haven't dispensed the new Comfort, so I couldn't even swear it's variable either. (I just have the Physio W3 and the S on my current formulary, budget PALs are typically fine in the old DRx anyway, I find.)

[bretk0923]

Hayde, as I understand it, the DRx is the only line in the series that is a full backside design that starts as a single vision blank. At least that's what my lab reps have told me. The "Enhanced" version is the digital dual-side mold of the old design, and the W2+ is basically just a re-release of that. They say the W2+ "incorporates newer technology", but good luck getting an answer out of an Essilor rep as to exactly what that means. Sorry, texan, for deviating from the original question.

It seems as though there's some conflicting information going on here (not surprising coming from Essilor). Whether the lenses are variable-length or not, the underlying point seems to be that the optician has no control over the corridor length here. Therefore, the combination of PAL selection and frame size cause an uncomfortable result for the patient. The two schools of thought for the solution are to either select a smaller frame, or use a fixed-length free-form progressive lens to control the positioning of the reading area. Personally, I tend to prefer the latter of the two, especially if the patient expresses a desire to use PALs over SV or a lined segment.

[Tallboy]

Thanks TB,

I haven't dispensed the new Comfort, so I couldn't even swear it's variable either. (I just have the Physio W3 and the S on my current formulary, budget PALs are typically fine in the old DRx anyway, I find.)

Yeah I dispense the DRX a and the Physio W3 only also. Never really got a Wow from clients who wore the S.

[Kwill212]

That sounds like a tough patient, and no multifocal will magically let her see every range at every desired angle. Unless she accepts that reality, I think she may be better off with multiple single-vision pairs--especially if you're still mastering PAL dispensing.

This is not a "tough patient". Unless the patient is holding the reading material in an obscure manner and refuses to read in a normal posture, this is progressive lens troubleshooting 101. As Dan said, corridor is too long, ADD is too weak, seg height is too low. I will add if this patient is a previous FT wearer, which is sounds like they might be, they are going to expect the full reading to be much higher than a traditional PAL. If that is the case a shorter corridor is better. However, you will need to explain this will reduce the usable intermediate. If the patient wants an everyday lens with a very high near zone, and a very generous intermediate then clearly that can't be had in one pair of spectacles. But, why are we suggesting someone with trouble getting to the reading zone should be in multiple pairs as a first course of action, and then blaming the patient for being a "tough patient"? We have to be better than this or we are going to go swiftly down the drain our profession is circling.

[Hayde]

This is not a "tough patient". Unless the patient is holding the reading material in an obscure manner and refuses to read in a normal posture, this is progressive lens troubleshooting 101. As Dan said, corridor is too long, ADD is too weak, seg height is too low. I will add if this patient is a previous FT wearer, which is sounds like they might be, they are going to expect the full reading to be much higher than a traditional PAL. If that is the case a shorter corridor is better. However, you will need to explain this will reduce the usable intermediate. If the patient wants an everyday lens with a very high near zone, and a very generous intermediate then clearly that can't be had in one pair of spectacles. But, why are we suggesting someone with trouble getting to the reading zone should be in multiple pairs as a first course of action, and then blaming the patient for being a "tough patient"? We have to be better than this or we are going to go swiftly down the drain our profession is circling.

My interpretation of 2020Texan's share was the patient was lifting the specs up high enough to get the reading zone in a lateral angle without a downward gaze. I cop to that take being assumptive on my part (reminding me of similar patients for whom I've fastidiously taped lenses so they can experience the reading angles prior to lens orders,) but it's no less an assumption that the patient wasn't lifting them so high--and is therefore a text-book troubleshoot just needing a more rapid add progression.

I'll leave it to others for now to decide what exemplifies why our profession circles a drain....

[lensmanmd]

As opticians, I believe we over think and under appreciate the sophistication of freeform calc engines. Variable corridors work for a majority of wearers. The corridors are calculated based on frame dimensions, PD and SH. Most wearers do wear their glasses in a "normal" position. The only time a custom POW should be used is for the patients that refuse to, or cannot, wear their specs in a normal position. And as opticians, we should be guiding our patients towards proper frame/lens combinations for best fit.

Just my 2 pennies from my years on both sides of the glass.

[Robert Martellaro]

Note the history- previously unsuccessful PAL wearer. Probably 20/25 or better uncorrected, using OTCs or Rx readers.

A pupil height of 30mm (about 6 above center) might sound plenty high, but these zyls tend to rest too low and close unless the bridge fit is textbook or have adjustable pads (a very short vertex distance will increase the downgaze angle need to acquire the near zone). Verify the pupil height measurement and evaluate the bridge fit.

I'm only slightly familiar with the Comfort 2 drx, but I'm reasonably sure the corridor is short enough for most Rxs, likely shorter than the Physios and S's.

Older folks will see better with brown tints instead of grey, especially over age 70. Not the main suspect, but possibly a contributor.

Post the Rx for more help.

Robert Martellaro

[2020texan]

My interpretation of 2020Texan's share was the patient was lifting the specs up high enough to get the reading zone in a lateral angle without a downward gaze. I cop to that take being assumptive on my part (reminding me of similar patients for whom I've fastidiously taped lenses so they can experience the reading angles prior to lens orders,) but it's no less an assumption that the patient wasn't lifting them so high--and is therefore a text-book troubleshoot just needing a more rapid add progression.

I'll leave it to others for now to decide what exemplifies why our profession circles a drain....

The patient was holding the readingcard in a normal position and length from her. But since the frame is so deep the reading area seemed very far down the lens and when shelifted the frame and found that sweet spot then she could read okay.Which is what brought up my question originally. That frame is so deep on her, the nasal reading area is way down where just looking down a gaze wasnt lining up her eyes into that area and she had to lift it. So that's why I was curious with such a deep frame if thatwas making the corridor in a way longer and thus her reading area much farther down.

[Hayde]

The patient was holding the readingcard in a normal position and length from her. But since the frame is so deep the reading area seemed very far down the lens and when shelifted the frame and found that sweet spot then she could read okay.Which is what brought up my question originally. That frame is so deep on her, the nasal reading area is way down where just looking down a gaze wasnt lining up her eyes into that area and she had to lift it. So that's why I was curious with such a deep frame if thatwas making the corridor in a way longer and thus her reading area much farther down.

Thanks for the clarification! For a Comfort DRx, excess B won't be the cause of problems. I assumed her historical PALs in a small frame were properly assigned a short channel and she was still unhappy. (Hardly a safe assumption, and if that's not the case my colleagues above speculating a short channel lens may cure her ills isn't a bad check.)

To clear up the ambiguity we've been tripping over, I'd suggest locating the patient's preferred angles of her specific reading tasks and mapping them on the lens. [Even a tall B zyl could be trimming the reading zone depending on PD & eyewire angle at the nasal.] If a short channel fitting chart lines up, great. If the patient is trying to read through the fitting cross like I inferred--then again I'd feel her out on single vision solutions.

I've bought a raffle ticket on this one, Tex...so keep us posted!

[bretk0923]

I've bought a raffle ticket on this one, Tex...so keep us posted!

+1. I'm VERY interested to see what the final result ends up being and how that compares to my own previous experience in similar situations.

This is why I love this forum. There's so many opticians of so many different backgrounds that all have different opinions and solutions that all come together in one spot. Really cool stuff.

[Pete Hanlin]

Welcome to Optiboard, 2020texan!

As Tallboy indicated, Varilux Comfort DRx (and Varilux Physio DRx) progressive lenses are FBS in format and do not have variable corridor. In a case such as the OP described (patient with deep frame wants to get into near quicker), you could order a Varilux Comfort DRx Short progressive lens, which will raise the near area as high as possible (practical) in the lens.

Varilux Comfort W2+ and Varilux Physio W3+ progressive lenses are automatically variable corridor- as the fitting height goes up the progression gets longer, and vice versa.

It should be understood, however, that in these products once you get above 17mm in fitting height, the progression will get no longer. This is because the eye has a limited range of "stress free" movement which must be respected for comfortable near vision. The limit of the eye's downward "relaxed movement" (i.e., the extra-ocular muscles are exerting no effort) is about 25 degrees. Beyond this level of rotation, the muscles have to expend an increasing amount of effort to keep the eyes in position (which is very uncomfortable- try looking down at the table without moving your head down for any length of time to see what I mean). Therefore, if a progression takes more than 11-12mm to get to reading, near vision comfort will be compromised.

Likewise, there are limits to how short a progression can be. Once you get below 8mm or so in length, the rate of change becomes to great to support stable intermediate vision (e.g., a 5mm progression becomes like a blended bifocal with a wide blend :^).

Anyway, point being you really should keep the progression between about 8-11mm for solid performance at near and intermediate- so there really isn't as much "variability" out there as one might think (well, you can go shorter or longer, but the PAL won't perform well at all distances).

[AngeHamm]

This is not a "tough patient". Unless the patient is holding the reading material in an obscure manner and refuses to read in a normal posture, this is progressive lens troubleshooting 101.

There's no reason it can't be both PAL 101 and a tough patient. If she's a repeat PAL non-adapt, that raises a number of red flags that standard troubleshooting is likely to be insufficient here. Remember that other opticians have troubleshot her (likely identical) problems in the past.

She may be one of the rare few who just prefers a shorter corridor even in a lens with a deeper B. I have worked with a handful of patients who prefer a more compact corridor rather than having to lift their chin another quarter inch.

[Tallboy]

She may be one of the rare few who just prefers a shorter corridor even in a lens with a deeper B. I have worked with a handful of patients who prefer a more compact corridor rather than having to lift their chin another quarter inch.

Shamir Intouch or other "Mobile Device" designs are kind of a blend of short corridors and full corridor lenses, they are a godsend to these people in my experience.

[AngeHamm]

Shamir Intouch or other "Mobile Device" designs are kind of a blend of short corridors and full corridor lenses, they are a godsend to these people in my experience.

Shamir InTouch is a miracle lens, in my experience.