Seven Years! What do you think of these ABOM ideas?

[William Walker]

I was in CE classes this past weekend, and the speaker was one of my teachers in opticianry school. In our CEs, a portion described the ABO Advanced exam, so he turned to me and asked about me experience taking and passing it. When I got home I had to look on my wall to see how long it's been - seven years! Oh my goodness!

Originally, I was working on one idea for an ABOM submission, but I went through a move to a new city, new job, etc... so it didn't fully materialize. I have the ability to renew my ABOA and thereby reignite that little spark to get my ABOM done.

I have a few ideas I've been bouncing around in my head, and would love to see everyone's thoughts.

1) Difference in impact resistance in poly/trivex with AR and without AR
a) I know that technically a scratch coating will lessen the impact resistance too, but a non scratch
coated lens isn't really an option in the real world.
b) The biggest dilemma I may have with this topic is the testing. We have standard drop ball tests
in our lab, but that's it. I don't really have a way to vary the test to push a material to it's limit.

2) A reference chart (with paper, obviously) that would establish a conversion between phoroptors for
refracted vertex distance. If you have a power patient and want to correct for vertex (and it's not
listed on the Rx), you could find which phoroptor the prescribing doctor used, and by measuring the
patient at your own phoroptor could site the chart to accurately know where the patient was
refracted at.
a) This could be a great resource if it's possible to do.
b) I could see using a number of test patients and measuring them in different offices (notating VD
and brand/model of phoroptor). I don't know a lot about phoroptors, so it makes me interested,
but I don't want to get half way into it, and find that each phoroptor could be individually set,
thereby negating my findings.
c) The other problem I could find is coming up with my measurements to create an accurate and
very usable chart, but not having enough 'tech' to write about and having it rejected.

3) Digital measuring devices - the role of the prefit. As spoke at length here on the boards, digital
measuring devices are great tools, but the optician has to be trained on how to use it properly. I
could write on common mistakes and what it does to the optics, and what the proper adjustments
for a range of fit should be.
a) If it seems to be too broad a topic, I could limit it to single vision only.
b) Not sure whether I should speak on digital measuring devices in general, or name one and use
that brand only in my paper. (I imagine the principles are all the same, but there may be enough
differences between brands to warrant specificity)

4) Adding AR to backside of sunglasses - difference in UV transmission from back to front of lens. AR is
designed for the visible light spectrum, but it might be neat to see if the backside AR lenses also
let more UV pass through to the front instead of being reflected back towards the eye.
a) I could broaden it to be UV transmission through AR lenses in general, and discuss any
difference in transmisison between AR vs non.
b) The only tester I would have is a standard UV meter, so the ability to measure this may be
difficult, as I'm not sure how I could distinguish between absorbtion vs reflection.

5) ??? Open to neat ideas, or things that lots of opticians have questions on.

Thanks for any input,
William

[Barry Santini]

As far as I can tell, non of the current digital centration devices can tease out/differentiate "absolute" pantoscopic angle from the combination of "posture + pantoscopic angle" Hoe about exploring the mechanics of doing that, and perhaps how, despite the fact that the DCDs don't always produce consistent measurements, that, for calc reason and *most* Rxs...it doesn't matter.

FWIW

B

[Diane]

William, I'm sure you enjoyed Bill's courses. I'm glad it sparked your renewed interest in your paper. I love some of your topics. Remember that you have a minimum number of words, but you could broaden your topic, so on 3, I don't think you would have to limit it to only SV. Colts Laboratory has some great information on impact on materials including poly and trivex. You may want a historical perspective on other materials as well, if you select that topic. I would be extremely interested in seeing this research from you.

I'm also interested in the effects of your AR topic. Each type of AR has an impact on vision. You may want to go to some of the "big boys". lens manufacturers to get them to share some information on that topic. They've got lots to share with you, and then you may find some way to do further testing. As a matter of fact, some of the gurus here on OB could have some tools they could share with you. :)

As far as another topic, with your combined certifications of CPOA with Opticianry, you may be able to draw from that as well. I'm seeing more of a reason for cross certification/knowledge in the optical industry as a whole. How can the advanced knowledge of lenses/frames/optics benefit a paraoptometric with their position?

Whichever topic you select, you will do a great job, I'm sure. All the best to you.

Diane

[Wes]

Both 1) and 4) are interesting to me. There was a thread on OB a while back regarding option 4. http://www.optiboard.com/forums/show...fe-So-Clear-So

[William Walker]

So let's say I was to go for option 1 - the difference in impact resistance between AR coated poly/trivex vs regular poly/trivex. For the actual values of impact resistance (pounds per square inch I assume), would a paper be accepted citing values from COLTS and possibly other sources, or would it have to be more of an experiment that I would have to somehow conduct myself?

[optical24/7]

Whatever your subject, make sure it's researchable with peer reviewed material. Stick to the Master's handbook on format. Good luck!

[Barry Santini]

Whatever your subject, make sure it's researchable with peer reviewed material. Stick to the Master's handbook on format. Good luck!

This was my problem. My ABOM paper was stalled for 2 years, as I did NOT use peer reviewed material. It was so outside the box.

B

[optical24/7]

Barry, I didn't do a paper on my preferred subject either. Unfortunately the master's committee does not want a "Subject that advances opticianry". They want a CE paper that they can research easily. ( And it still took over 3 months to hear back from them!)

[Darryl Meister]

As far as I can tell, non of the current digital centration devices can tease out/differentiate "absolute" pantoscopic angle from the combination of "posture + pantoscopic angle"

Ultimately, the angle that matters is the angle that the plane of the frame makes with the line of sight at its inserction with the fitting point of the lens. A properly leveled device that measures the fitting point without parallax can simply measure the plane of the frame from vertical. If the patient has not assumed his or her habitual posture, the error will be in the height of the fitting point measurement, which traditional fitting technique is even more likely to produce, not in the tilt measurement.

Best regards,
Darryl

[Barry Santini]

Ultimately, the angle that matters is the angle that the plane of the frame makes with the line of sight at its inserction with the fitting point of the lens. A properly leveled device that measures the fitting point without parallax can simply measure the plane of the frame from vertical. If the patient has not assumed his or her habitual posture, the error will be in the height of the fitting point measurement, which traditional fitting technique is even more likely to produce, not in the tilt measurement.

Best regards,
Darryl

Excellent! Yet, with Sheedy's work revealing that people prefer a mild eye depression angle for maximum comfort, averaging 3 to 6 degrees, then how would a DCD integrate this factor into an ideal fitting height scenario? Answer: I think it wouldn't. So the intersection with the fitting point of the lens still has a bit of grey zone around it "absolute" value, along with true panto angle for eye CR alingment reasons.

Me thinks that we shouldn't get too hung up here on millimetric precision, which brings out the OCD in almost every optical professional I know. Does that mean we should not measure and fit lenses using POW values? Absolutely not. But any experienced ECP has encountered situations where people are known to "like" their progressives slighter lower than higher, and I think the main conributing factor is Sheedy's eye depression comfort angle. With this in mind, DCD's cannot be relied-upon for absolute values in vertical fitting points.

FWIW

B

[Robert Martellaro]

<snipped> I know that technically a scratch coating will lessen the impact resistance too <snipped>

I've read that some cushion and hard coats actually increase the lenses impact resistance. Moreover, a scratched lens is generally a less impact resistant lens. Food for thought, although it's all probably moot because most lenses sold will have an AR stack.

[Darryl Meister]

then how would a DCD integrate this factor into an ideal fitting height scenario? Answer: I think it wouldn't.

You seem? to be implying that this is a limitation of digital centration systems, but this situation doesn't affect digital centration systems any more than it affects traditional lens fitting. Progressive lenses are generally fitted to pupil center when the wearer looks straight ahead, which represents a fairly stable reference position for the optician. However, if wearers generally have a habit of walking around or driving with their lines of sight at some arbitrary angle of downgaze, I suspect that the best approach would be to compensate for this effect in the actual lens design, by reducing the plus power below the fitting cross, for instance.

Best regards,
Darryl

[Darryl Meister]

I've read that some cushion and hard coats actually increase the lenses impact resistance. Moreover, a scratched lens is generally a less impact resistant lens. Food for thought, although it's all probably moot because most lenses sold will have an AR stack.

"Cushion" coatings, like the name implies, are generally designed to increase impact resistance by dissipating some of the impact energy, particularly when the lens has been hard coated. Generally, hard coatings will reduce impact resistance. Since a hard coating is more brittle than the plastic lens substrate, the coating will crack more easily when struck, causing the substrate beneath it to tear apart, just as it is easier to tear a plastic bag that already has a small notch in it.

The tensile strength of the lens material and the center thickness of the lens are probably the single greatest factors influencing impact resistance, followed by the application of any brittle coatings, the edging quality, the base curve of the lens, and so on. And, as Robert noted, any damage to the lens will reduce impact resistance, since it serves as a point of origin for fracture propagation, particularly in glass.

The type of impact is also an important factor, because some lenses may perform worse against a high-mass, low-velocity impact, whereas some lenses may perform worse against a low-mass, high-velocity impact. The analogy would be a slow-moving bowling ball compared to a fast-moving bullet. This is why the ANSI Z87.1 safety standard has tests for both types of impact. In any event, it would be an interesting topic to write on with plenty of research available in the literature.

Best regards,
Darryl

[Barry Santini]

You seem? to be implying that this is a limitation of digital centration systems, but this situation doesn't affect digital centration systems any more than it affects traditional lens fitting. Progressive lenses are generally fitted to pupil center when the wearer looks straight ahead, which represents a fairly stable reference position for the optician. However, if wearers generally have a habit of walking around or driving with their lines of sight at some arbitrary angle of downgaze, I suspect that the best approach would be to compensate for this effect in the actual lens design, by reducing the plus power below the fitting cross, for instance.

Best regards,
Darryl

Not a limitation. Rather, a limit to one's "expectations" of them. Your point is well taken re: traditional manual methods. I think that many who champion/believe devoutly in DCD do not understand what they can reasonably be expected to do. They are far superior for most in the values they deliver. But they me be no better than those who excel at measurements manually, without interpretation factored in. Both require this.

B

[harry a saake]

Not a limitation. Rather, a limit to one's "expectations" of them. Your point is well taken re: traditional manual methods. I think that many who champion/believe devoutly in DCD do not understand what they can reasonably be expected to do. They are far superior for most in the values they deliver. But they me be no better than those who excel at measurements manually, without interpretation factored in. Both require this.

B

Darryl, i also wonder about internal flaws in poly , trivex and cr-39. We know there are what is called griffith flaws in crown glass, and i,m wondering now what there might be and how they are termed in the way of flaws internally in these other materials, and how that might effect impact resistance

[Darryl Meister]

i also wonder about internal flaws in poly , trivex and cr-39. We know there are what is called griffith flaws in crown glass, and i,m wondering now what there might be and how they are termed in the way of flaws internally in these other materials, and how that might effect impact resistance

Yes, Griffith flaws at the surface of glasses and ceramics limit the tensile strength of these materials. Plastics and ductile materials are less susceptible to fracture due to Griffith flaws though. Internal defects in glass would be more like striae and inhomogeneity.

A lot of improvements have been made in the quality of polycarbonate materials, mainly due to the optical disc industry I imagine, but internal defects are still possible with plastics. And some localized internal strain as a result of different casting or injection-molding techniques is not uncommon. This strain may reduce impact resistance in some cases, if it is sufficiently high, or lead to edge cracks and such.

Best regards,
Darryl

[harry a saake]

Yes, Griffith flaws at the surface of glasses and ceramics limit the tensile strength of these materials. Plastics and ductile materials are less susceptible to fracture due to Griffith flaws though. Internal defects in glass would be more like striae and inhomogeneity.

A lot of improvements have been made in the quality of polycarbonate materials, mainly due to the optical disc industry I imagine, but internal defects are still possible with plastics. And some localized internal strain as a result of different casting or injection-molding techniques is not uncommon. This strain may reduce impact resistance in some cases, if it is sufficiently high, or lead to edge cracks and such.

Best regards,
Darryl

Darryl, good info, glass with the griffith flaws is well identified, are there any names that are associated with these flaws in poly , cr-39, or trivex, also how do you see them or detect them if at all

[Darryl Meister]

glass with the griffith flaws is well identified, are there any names that are associated with these flaws in poly , cr-39, or trivex, also how do you see them or detect them if at all

I'm pretty sure that all materials can have surface or Griffith flaws, but these flaws do not reduce the strength of metals and plastics as much as with glasses and ceramics, because a region of plasticity exists around these flaws in metals and plastics, which are more ductile, and this region dissipates the strain to some extent and converts it to heat.

Best regards,
Darryl