Autograph II *SV* fitting instructions

[Barry Santini]

After quite a bit of research, please note the following points about fitting Auto II SV:

1. The *engraved* circles (like you receive on a progressive) are to be fit "ON PUPIL", i.e., there is a ZERO mm difference in the fitting cross from the MRP. The MRP/PRP and fitting cross are one and the same.
2. Although Auto II SV DOES NOT iterate the design for PD and Pupil height or frame info, it *will* calculate and add "prism thinning" (up to a maximum of 2.5 diopters) to reduce any "wedge" that would be evident. In some cases, however, some vertical prism wedge in the completed job may be evident.
3. The amount of prism thinning applied will be noted on the job's "POW" information block. This prism can be verified at the level of the engraved circles (as noted above).
4. Because of the prism thinning, one SHOULD NOT use theconventional and familiar "OC" in layout for edging or neutralizing.

As Dr. McDonald has pointed out, the ophthalmic dispenser is no longer a job "any dummy can do"
(and that goes for frame *stylists* TOO!)

Confusing? Yes.
Counter-intuitive? Yes.
They way it is for now? Yes.

FWIW
Barry

[Robert Martellaro]

After quite a bit of research, please note the following points about fitting Auto II SV:

1. The *engraved* circles (like you receive on a progressive) are to be fit "ON PUPIL", i.e., there is a ZERO mm difference in the fitting cross from the MRP. The MRP/PRP and fitting cross are one and the same.
2. Although Auto II SV DOES NOT iterate the design for PD and Pupil height or frame info, it *will* calculate and add "prism thinning" (up to a maximum of 2.5 diopters) to reduce any "wedge" that would be evident. In some cases, however, some vertical prism wedge in the completed job may be evident.
3. The amount of prism thinning applied will be noted on the job's "POW" information block. This prism can be verified at the level of the engraved circles (as noted above).
4. Because of the prism thinning, one SHOULD NOT use theconventional and familiar "OC" in layout for edging or neutralizing.

As Dr. McDonald has pointed out, the ophthalmic dispenser is no longer a job "any dummy can do"
(and that goes for frame *stylists* TOO!)

Confusing? Yes.
Counter-intuitive? Yes.
They way it is for now? Yes.

FWIW
Barry

But if this design does not compensate for panto tilt, we'll need to drop the OC .5mm per degree of tilt, minimizing off-axis errors due to the aspheric/atoric surface, and on-axis errors when there is sufficient power.

So it seems to me that the vertical OC height needs to be specified at the time of order, and that prism thinning should be avoided, especially for minus powers where the yoked prism would probably be base up.

Therefore, if the PRP is aligned with the engraving circles, then the circles will not be aligned with the pupil center, but lowered by an amount that corresponds to the degree of panto. Which leads to the question why is Shamir asking for the fitting cross position/pupil center height, instead of the OC height that will align the optical axis of the lens with the center of rotation of the eye (Martin's formula for tilt)?

[Barry Santini]

Good Points, Robert!

I'll send a tech question to Shamir and discover what (if any) panto default value the current fitting guide protocol is referenced against.

Will let you know what I find.

Barry

[Chris Bowers]

The Major Reference Point (MRP) is the point from
which calculations are made to process the lens. The
Major Reference Point is also referred to as the Prism
Reference Point (PRP). The Fitting Point is the point
directly opposite the pupil. When processing a
Prescribed Prism, you can set the Major Reference
Point to be at the Fitting Point
All Aspheric lenses have a pole or center that need to be positioned at pupil center. It is the aspheric deign that is minimizing the off axis errors and is running at predetermined values. In cases of extreme pantoscopic, wrap and vertex use the attitude lens which can have these individual custom values applied.
Prism thinning is an individual lab’s choice as to default or not and as to threshold values.

Hope that helps!

[Robert Martellaro]

Barry,

By all means, post any info you can acquire. I'll do the same. After all, we want to get this right.

Walman/Soderberg is not prism thinning this lens. The OC's have been right on the PRP.

I believe much depends on how much of Shamir's Eye Point/ray tracing program is used for this lens. My guess is that very little if any optimizations beyond the ocular surface atoricity. If true, we should probably fit like any other aspheric/atoric lens: OC .5mm down per degree of panto. I don't see how it can be any other way if they're not asking for the panto value, unless they are using a default value. However, there should be a compensated Rx if the OC is at the pupil height, and I'm not seeing any compensation.

[Barry Santini]

Thanks, Chris!

What are the "predetermined (fitting) Values?"

Barry

[Laurie]

Hi Guys,

There was the opportunity for confusement among ECP's in regard to vertical OC heights...

therefore,


Providing the fitting height rather than vertical OC placement provides the software and lab to go with similar prism thinning as they do for PALs. Verifying according to distance gaze with a 'sv fitting cross' rather than dropping the OC's/per mm of tilt makes sense.

As much as we have discussed vertical OC heights/Martin's Rule of Tilt, ect. here and at CE seminars, the lens is catching on at a faster speed than that of specific fitting instructions.

If the ECP is ordering according to vertical OC height, they have to adjust/measure for tilt/OC displacement rules. If they are not sure how to do this, than the client/patient will not receive the full benefits of personalization.

If the ECP supplies the fitting height, as they would for a PAL, the design will incorporate it as they do PAL designs, with equi-thinning.


Barry hit it earlier, we really need to get the word out, temple-bending won't cut it in light of technology/fitting advances. I can only add, that, getting new information out and educating our profession of new fitting paradigms is a big job...we'll get there.

: )

Laurie

[Barry Santini]

Laurie<

I love your posts, but I'm *still* confused.

Here's what I thinkin':

1. Martin's formula for tilt applies to spherical lenses, and optimizes the "optical center" placement in front of the eye through compensation for values different from "0" for pantoscopic tilt. This "adjustment" ensures that the "optical axis of the lens will pass through the center of rotation (CR) for the eye, and therefore the spherical *corrected-curve* benefits of the lens design are fully realized as the lens designer intended. In these lenses, the traditional "optical center" and the lens design "pole" are one and the same.

2. Apheric lenses have, in most cases, required that their lesn design "pole" be placed in front of the pupil to deliver the intended design benefits. In most of these designs, the "optical center" and the "design pole" are still one and the same, and by placing this OC/pole in front of the pupil, the "polar" (and optical) axis of this design will intersect the CR of the eye.

3. The Shamir Autograph II SV design does the same, but, somewhat counter-intuitively in view of the above, allows "prism-thinning" for cosmetic purposes *only*, up to 2.5 diopters, without affecting the intended lens design benefits, as long as the MRP/Fitting Point is placed in front of the pupil. Here, the traditional "optical center" and the design "pole" are sometimes separated, depending the the relationship of the found pupil height to the geometric center/datum line of the chosen frame.

Both #2 & #3 aspheric lenses performed as intended when the lens design *pole* is placed directly in front of the pupil. Martin's formula for tilt does not apply, since the "OC" of these lenses is not the primary fitting parameter to ensure that the design aligns properly to the CR of the eye.

Optiboarders with brains much better than I, please help here!!!

Barry

[Chris Bowers]

Perfect!

[Robert Martellaro]

2. Apheric lenses have, in most cases, required that their lesn design "pole" be placed in front of the pupil to deliver the intended design benefits. In most of these designs, the "optical center" and the "design pole" are still one and the same, and by placing this OC/pole in front of the pupil, the "polar" (and optical) axis of this design will intersect the CR of the eye.

If there is no panto. If there is panto (and there almost always will be) then the OC should be lowered according to Martin's Formula/Rule for tilt.

http://www.eyecarebiz.com/article.aspx?article=50510

http://books.google.com/books?id=Zl4...46&dq#PPA46,M1

[Barry Santini]

If there is no panto. If there is panto (and there almost always will be) then the OC should be lowered according to Martin's Formula/Rule for tilt.

http://www.eyecarebiz.com/article.aspx?article=50510

http://books.google.com/books?id=Zl4...46&dq#PPA46,M1

Thanks for the add'l info, Robert. However, it further complicates my understanding as to *why* the Auto II lenses *must* have their design pole in front of the pupil, and not adjusted as with the aspheric lenses you cited.

?????

barry

[Robert Martellaro]

Thanks for the add'l info, Robert. However, it further complicates my understanding as to *why* the Auto II lenses *must* have their design pole in front of the pupil, and not adjusted as with the aspheric lenses you cited.

?????

barry

Unless the "pole" is decentered down. But there will still be an increase in power and induced cylinder on-axis, primarily for powers above 5D. Looks like we'll have to call Israel. Anyone know which Kibutz the lens designer lives in?

[Laurie]

Hello Again,

Barry, (love your posts too) : )

I follow your logic. The only part that doesn't quite fit, IMO, is:

In most of these designs, the "optical center" and the "design pole" are still one and the same, and by placing this OC/pole in front of the pupil, the "polar" (and optical) axis of this design will intersect the CR of the eye.

When there is zero panto, this is true...When there is panto (almost 100 percent of the time), the OC will not be at the same location as the 'optical pole', which would line up with the MRP/PRP. This, if I am understanding 'optical pole' to correlate with 'optical axis', or 'the part of the lens/optical system in front of the eye which intersects the circle of rotation'

(As Robert stated),...When panto is added, the OC will be lower, (1mm per 2degrees), and the optical axis (I also like the term optical pole here) will be in front of the pupil.

clear as mud?
clear as crown glass?

: )

Laurie

[Barry Santini]

Yes, Laurie, it's clear now.

But...

Why can Auto II SV mandate that the Fitting point be in front of the pupil, regardless of panto ( zero or not).

Barry

[Chris Bowers]

I sent this thread to a friend of mine in Israel. He is one of the software Guys for Shamir. I hope he will reply!

[Robert Martellaro]

This, if I am understanding 'optical pole' to correlate with 'optical axis', or 'the part of the lens/optical system in front of the eye which intersects the circle of rotation'

Laurie,

I've not heard the term "optical pole" before, but it sounds like the geometric center of the lens, a zero, or design reference point for the surface asphericity. The OC should be at the same spot except when there is prescibed prism. A single ray traveling through the lens at this point will be perpendicular to the plane of the lens, and is called the principle axis.

But the questions remains: why is Shamir asking for the vertical height for the primary gaze (looking straight ahead)?

I sent this thread to a friend of mine in Israel. He is one of the software Guys for Shamir. I hope he will reply!

When all else fails, bring out the big guns. Thanks Chris.

[HarryChiling]

Here's my 2 cents, the aspheric center (optical pole) must be aligned with the center of rotation. If Shamir is applying prism thinning, to a SV lens then this is independent of the compensations to the prescription or the way the lens is tilted or set in the frame.

I would fit the aspheric center according to the amount of tilt, using Martins Rule or a more accurate version incorporateing vertex if that is significantly different than the 28.6mm center to back vertex used in martins rule.

If prism thinning is OK for SV lenses, then we can't treat it like it's an alien concept, it is exactly like prism thinning for PAL's except applied on SV lenses.

[drk]

Man, I'm confused, but what HC says makes sense.

Firstly, why prism thin? We never have prism thinned SV before.

Secondly, it seems an immutable law of physics that the optical center of any lens, regardless of surface curvature, should be moved downward with pantoscopic tilt according to our familiar formula, as has been said, so the optical axis of the lens intersects the eye's center of rotation.

Thirdly, how Shamir opts to mark their lenses or choose their own reference points is totally secondary.


Please help me out.


Now I'm going to make a guess or two:
As Robert said, they are certainly individualizing with "the perfect" base curve for the sphere and atoricizing the lens.

I'm going to assume that they also want to individualize for the position of wear, and you are to supply the vertex (as Harry mentioned), and panto, maybe face-form/dihedral/frame wrap.

They will incorporate all this POW info into the design, but you will always deal with a consistent pupil-centered fitting cross, like on progressives. However the power read at the fitting cross will be compensated power, compensated prism, etc. Something consistent, and something that's always "compensated" to keep our noseyness out of the picture.

As to prism thinning, I guess when they made up a few of these monsters, they decided that the bottoms may look thick, especially to dispensers who never took vertical measurements and fit at 1/2 B by default.

[Chris Bowers]

Wouldn’t prism thinning on SV be bilateral nonsense?

[Barry Santini]

drk:

Auto II SV *does not* use any POW compensations in its fabrication, at this time.

To my knowledge.

However, the discussion above points up one fact to me:

Despite no POW compensation (esp for panto), Auto II SV delivers alot of WOW for those astigmats over 0.50D, at least in my experience.

And those wows have come with (my) inattention to proper fitting protocol, Martin's formula or not.

So: What's the most important contributor here?

1. Atoric optimization
2. Bells & whistles
3. Power of suggestion ("You'll get HD vision with these")
4. all of the above.

Vote - no poll.

Barry

[drk]

Base curve and atoric.

[HarryChiling]

I would vote 1 and 3, and to compensate every thing is just unnecessary and overly complicated in the first place so i would be glad that they don't include POW compensations in the lenses. For the most part fitters need to focus on fitting the proper frame and lenses, and also properly adjusting them, that means no patients with a 59mm pd in a honking aviator. Even if the optics can be compensated to provide good vision the frame should be avoided. I learned a rule that I have used that suits me well, 0 to 3mm decentration is optimal anything outside of this and you need to justify it. Consequently if this rule is followed you'll find that a 15 degree faceform and up to a 15 degree panto are optimal.

We have come to the point where lens technology is trying to replace good fitting skills.

[Barry Santini]

We have come to the point where lens technology is trying to replace good fitting skills.

Normally Harry, I'd take issue with a statement like this...

...if it didn't ring sooo true!

Barry

[HarryChiling]

Normally Harry, I'd take issue with a statement like this...

...if it didn't ring sooo true!

Barry

I guess someones gotta fix it.

[Jacqui]

Instead of trying to guess what to do, why not contact an expert?? Crickett13(sp), Matt Balester is on the Shamir USA technical staff and would probably have much more info.