Rx Compensator

[jhorn]

Can anyone advise me on where I get the pantoscopic tilt degree and the wrap degree for a sunglass frame? I called marchon they have no idea what I'm talking about. I want to use the rx compensator for a wrap sunglass.

[Darryl Meister]

I created the attached Basic Frame Wrap Angle protractor earlier tonight, which should allow you to approximate face form wrap. Its use should be self-explanatory, but post if you have any questions.

Pantoscopic tilt can only be measured with the frame on the wearer. ZEISS actually makes a simple tool to measure pantoscopic tilt and vertex distance for the Gradal Individual free-form progressive lens; you can ask your local Carl Zeiss Vision representative about the availability of the tool. When using the Rx Compensator program, if you don't know that pantoscopic tilt, just leave it at 0.0 degrees.

[Cherry Optical]

I created the attached Basic Frame Wrap Angle protractor earlier tonight, which should allow you to approximate face form wrap. Its use should be self-explanatory, but post if you have any questions.

Pantoscopic tilt can only be measured with the frame on the wearer. ZEISS actually makes a simple tool to measure pantoscopic tilt and vertex distance for the Gradal Individual free-form progressive lens; you can ask your local Carl Zeiss Vision representative about the availability of the tool. When using the Rx Compensator program, if you don't know that pantoscopic tilt, just leave it at 0.0 degrees.

Thank you, thank you, than you.

Adam

[Florida Optician]

Help! From a labs stand-point does anyone have a suggestion on how to plainly and clearly explain to our clients (opticians, OD's and MD's) how this works so that they can understand it well enough to be able to then explain to their customer.We are encountering resistance to some of the new lens products out that require compensated RX's-with the valid point that how will the next optician down the road know that what they are looking at is a compensated RX and not just made incorrectly. We are frustrated because our clients are frusutrated.
Thanks-

[Grubendol]

That's awesome Darryl, thanks! It's already attached to my desk.

[HarryChiling]

Help! From a labs stand-point does anyone have a suggestion on how to plainly and clearly explain to our clients (opticians, OD's and MD's) how this works so that they can understand it well enough to be able to then explain to their customer.We are encountering resistance to some of the new lens products out that require compensated RX's-with the valid point that how will the next optician down the road know that what they are looking at is a compensated RX and not just made incorrectly. We are frustrated because our clients are frusutrated.
Thanks-

The make a machine that would put some sort of mark on the lens so when fogged with lets say you breath a symbol would appear. If this could somehow incorporate the tilt angle and wrap angle the rx could be put back through the compensator at a negative tilt and wrap angle with the correct rx being produced. Just a thought from a labs standpoint.

[Darryl Meister]

From a labs stand-point does anyone have a suggestion on how to plainly and clearly explain to our clients (opticians, OD's and MD's) how this works so that they can understand it well enough to be able to then explain to their customer.
First and foremost, you should always make the compensated prescription available, and note any changes in your patient record (including the frame fitting details used for the compensation). It is especially important to provide dispensers responsible for verifying power with a copy of the compensated prescription. I would also show the patient both the original and compensated prescriptions, and explain the difference. A discussion with the original prescriber to ensure that everyone is on the same page is never a bad idea, either.

There are several articles available on prescription compensation (from guys like Blendowske, Keating, Harris, etcetera). You could always supply a copy of one of these to doctors who are unfamiliar with the concept, and remind them that it is very similar to compensating for factors such as vertex distance. You can also download a paper I wrote on optical optimization and prescription compensation from this thread (http://www.optiboard.com/forums/showthread.php?t=18852). (This was written for free-form lenses, though the prescription compensation principles apply to all lenses.) If you have a doctor who is particularly resistant to the idea though, I would just avoid compensating his or her prescriptions.

And remember that compensation really only becomes meaningful in moderate to high prescriptions with significant amounts of lens tilt.

[HarryChiling]

For some reason

If this could somehow incorporate the tilt angle and wrap angle the rx could be put back through the compensator at a negative tilt and wrap angle with the correct rx being produced. Just a thought from a labs standpoint.

isn't working in Darryl's or my calculator, although I think it should work. I will have to go over the math when I get home and check it out.

[Darryl Meister]

isn't working in Darryl's or my calculator, although I think it should work.
I'll save you the trouble: It won't work. ;) In most cases, you'd just be doubling the amount of compensation involved. You'd basically have to solve some of the equations in reverse order, instead.

[HarryChiling]

What about an Rx de-compensator program? This would be awesome.

[HarryChiling]

Darryl, if I know you. This is the quiet before the storm. Are you working on an Rx decompensator, cause if you are it's a race. ;)

[Darryl Meister]

Darryl, if I know you. This is the quiet before the storm. Are you working on an Rx decompensator, cause if you are it's a race
Nah, I've been visiting family over the weekend.

Also, because of the number of calculations involved in my current program (including prism due to thickness, lens tilt due to meniscus decentration, and so on), it would really be impractical to do anything but a very simplified version.

And I don't know that anyone would find it nearly as useful as the regular version.

[Glenn Bolton]

Darryl, Is you program available to download??

[Darryl Meister]

You can download the current version from this thread (http://www.optiboard.com/forums/showthread.php?t=19366). But be sure to check back in a month or two though; I plan to have something really neat available by then... ;)

[lpsouth1978]

Can anyone tell me what the PA is in the frame wrap compensator? It is a terrific tool, but I need to know what that measurement is.

[Cherry Optical]

Can anyone tell me what the PA is in the frame wrap compensator? It is a terrific tool, but I need to know what that measurement is.

I assumed it was prescribed ADD.

Adam

[Cherry Optical]

You can download the current version from this thread (http://www.optiboard.com/forums/showthread.php?t=19366). But be sure to check back in a month or two though; I plan to have something really neat available by then... ;)

Its been a month.... Have anything really neat ready?

Adam

[Darryl Meister]

Can anyone tell me what the PA is in the frame wrap compensator? It is a terrific tool, but I need to know what that measurement is.
It stands for Pupil Above, and represents the position of the pupil center above the optical center of the lens, which is typically placed along the datum (180) line of the frame for single vision lenses. Consequently, you can usually calculate the PA from Pupil Height - 1/2 B. Generally, it will be between 2 to 5 mm. You can find a list of the field abbreviations on the Help page.

Its been a month.... Have anything really neat ready?
It's very close. ;) I'm on vacation next week, so hopefully I'll be able to do some more work on it...

[Cherry Optical]

It stands for Pupil Above.

Wow! I wasn't even close! LoL. I probably made 20 pair of lenses with the ADD power in the PA field. LoL. Ooops.

Not the first mistake I've made and not the last I'll make.

Adam

[Darryl Meister]

Wow! I wasn't even close! LoL. I probably made 20 pair of lenses with the ADD power in the PA field. LoL. Ooops
The good news is that the add power usually isn't far off from typical Pupil Above values! Essentially, the program backs out on some of the pantoscopic tilt compensation when the pupil is above the optical center, in accordance with the rule of thumb for lens tilt (that is, there should be 2 degrees of tilt for every 1 mm of drop between the optical center and the pupil).