Pt. refers to the corrected lenses out of focus. Doctor says we made his Rx wrong.
Example: Dr's Rx
R- -7.75 -0.50 x 051
L- -6.75 -0.50 x 150
Lab optimized Rx digital surfaced lenses
R- -8.13 +0.79 x 144
L- -7.10 +0.67 x 050
Everything seems to check out ok
but Pt. can't focus
Changed material Poly aspheric & used Dr's Rx
Pt. sees fine.
The optimized rx seems to work on wrap frames
but not reg. street wear :hammer:
I think the lab needs to OPTIMZE it's software a little more!Originally Posted by smith,jimbob
Pt. needs contacts. Odd you changed to poly and he could see, usually it's changing from poly that makes people see.
The vertex distance is probably different between the dress specs. and the sun specs. With a script that high if there is a difference the pat. is going to see it. It's always a good thing to fill a script without any modification. If the script has been filled to the Dr's. spec., and the pat. has problems not related to how the lenses were fitted, the egg's on their face.
I have seen in some cases where folks have had trouble with higher refractive index materials.
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Hmm, jimbob from Columbus? Ok, I'll play.
Labs don't transpose minus cyl to plus cyl. If they did, tell them to cut it out. If you did it, then you cut it out.:)
Looking at the right eye, the compensated power is about what you would expect if the panto is ten degrees, wrap six degrees, and the vertical OC at center pupil, or the OC at some unknown distance below the pupil with less panto.
Check the vertical OC position.
Last edited by Robert Martellaro; 02-14-2011 at 10:56 PM.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Agree with Robert. For me, I would have trialed a -0.25D flipper over BOTH pairs, and seen the patient saw distance "better". That would reveal if the RX was undercorrected.
B
This scenario shows an example of the need for a prescription decompensator, the vertex compensation formula is available in the ANSI standards so it is easy to decompose a vertex compensated lens to determine the values used to compensate and how it was done. Currently no standard exists for prescription compensation for tilt and wrap. I hope that eventually a standard can agreed upon or any company compensating at least provides a program to decompensate the lens so that it can be determined if the lab provided the correct compensation.
I had an excel sheet that provided a decompensation for Blendowskis algorithm if I can find it I will post it but their is no guarentee that the manufacturer that you used uses that particular algorith and the formulas are still third order approximations which means it won't provide an exact ray traced compoensation.
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Keep in mind that you really don't need a "decompensation" program to compare your compensated prescription with the results of an existing compensation program. Since you can always plug your original prescription and position-of-wear parameters into an existing compensation program, you can also compare the results of the software with the compensated prescription that you receive from the laboratory.
That said, most public domain prescription compensation programs rely on fairly simple calculations based upon several approximations. More advanced free-form lenses are calculated using ray tracing, as you noted, which is more accurate. So, if you compare a compensated prescription for one of these lenses against the results of a less sophisticated prescription compensation (or even "decompensation") program, you are likely to see differences either way.
Best regards,
Darryl
Darryl J. Meister, ABOM
I agree that you should double-check your the measurements that you supplied for the position of wear. If the fitting measurements do not actually match what the patient is actually wearing, the patient will not experience the prescribed powers in the position of wear.
And, of course, ensure that the laboratory actually fabricated the prescription correctly (against the compensated Rx). The fitting heights and mono PDs should also be verified. Too often with these new lenses, the most common sources of error are overlooked in lieu of the less well understood features, like prescription compensation.
Best regards,
Darryl
Darryl J. Meister, ABOM
Thorny issue.
It shows that we really have a degree of uncertainty in everything we do.
For example, in a non POW-compensated Rx, we'd always have to wonder what the refracting conditions were (panto/faceform* of the phoroptor head, vertex distance). In a POW-compensated Rx we don't know what exact protocol was used (not to mention that the unspecified original refracting conditions error is in play for these cases as well!).
The bottom line is that we don't know what the lenses should be, anymore! At least with non-compensated, you have the illusion that the lenses as read in your lensometer match the prescription, but with compensated?
Ultimately, it will come down to the patient's visual performance, as it did in this case. While this is a squishy standard, it's the bottom line. I don't like it, but there's more slop in the vision-correcting process than we care to admit. There's slop in a patient's psychology as well, though.
In this case, we don't know enough about the patient. If the patient has, presumably, near-point blur with the new glasses and is emerging presbyopic, well DUH. If the patient's lens powers have increased more than a nominal 1/2D, then some near-point adaptation is quite common. The refraction may be overminused**. Who knows? Maybe they just stopped complaining after all the ensuing fuss. We'll never know.
It would be nice to have more information, but look at what we know.
Dr's Rx...
R -7.75 -0.50 x 051
L -6.75 -0.50 x 150
Lab supplied...
R -7.34 -0.79 x 54
L -6.43 -0.67 x 140
Using your Rx compensator 2.3 program, I inputted Vtx 13.5, wrap 6 panto 10, all of which are very close to most softwares default values, no horizontal decentration, OC level with pupil, and 1.60 index. Here's what it spits out!
R -7.34 -0.80 x 54
L -6.44 -0.67 x 140
It could be as simple as the lab software not having an input for the fitting point on a SV lens, incorrectly using the OC height field instead. I recently had a similar problem with the new Shamir Auto SV and my lab's DVI software. IMO, Zeiss handles this much better, and unless you need Trivex, I'd recommend their lens.
So even if this isn't an optom student shooting a hypothetical across our bow, it does show us the significance of having good communication with the lab, and that we understand how this technology works before putting it on the dispensing table.
Only when people are involved!
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
That seems incredibly close, given that my software wasn't actually written to handle the complexities of progressive lenses. It could be luck or they could be using an Rx compensation program (like Rx Compensator), instead of a true optical design engine.Using your Rx compensator 2.3 program, I inputted Vtx 13.5, wrap 6 panto 10, all of which are very close to most softwares default values, no horizontal decentration, OC level with pupil, and 1.60 index. Here's what it spits out!
Jimbob, what product are you using, exactly?Pt. refers to the corrected lenses out of focus. Doctor says we made his Rx wrong
Best regards,
Darryl
Darryl J. Meister, ABOM
It seems then that the corporation has purchased a generic software package. One formula fits all. Corporation sold this as a process of widening the visual field at the optical center point. The lenses seem to be Seiko's Proceed lenses. It was suppose to correct flaws do to Snell's Law in a normal Rx. Rx prescription is corrected for right and left lens individually to max correctness for frame curve, prescription, vertex distance, and wrap. It may be that associates' are taking measurements with enough care or if the software package sets every Rx at 13.5 vertex, 6 wrap, and 10 degrees pano. Later this year we are to be getting an electronic measuring device that is attached to the pt.'s frame for more accurate measurements. I have not seen it, but reminds me of the Grolman fitting device I tried to sell in 1978 for AO.
Thanks for all the insights. I feel way behind responders as I'm still running a Coburn 113 everyday
Best regards, Jimbob
Unfortunately, if they are simply using a basic prescription program, instead of a truly optically customized lens design, you will not be maximizing the optical outcome. Although these programs represent an improvement over offering no optical refinement at all, they will not provide the level of performance of a real-time optical design engine that applies point-by-point aspheric corrections over the entire lens based on the position of wear.
Best regards,
Darryl
Darryl J. Meister, ABOM
I am trying to figure out why the Rx was optimized with a + cyl
I have only been doing this for 7 years and I can't say as I ever had the urge to transpose to a + cyl when I have to transpose them when the ophthalmologist writes them in + cyl format
what is the Rx being optimized for? Is the Rx being made for a digital lens?
Just wondering I haven't been doing this as long as some of you.
Lux labs transpose to + cyl, always wondered why they do that
Basically this lab is trying to "Digitally Enhance" conventional progressives with a basic compensation program that takes into account POW values but not lens design. I'm willing to be that if you ordered this lens in any progressive style or even ST-28's it would spit out the same compensated power.
As many have pointed out previously,you can clean up some of the back surface issues with the proper software and a digitital generator IF the software takes lens design into account. Otherwise you are merely making more accurate errors.
There are rules. Knowing those are easy. There are exceptions to the rules. Knowing those are easy. Knowing when to use them is slightly less easy. There are exceptions to the exceptions. Knowing those is a little more tricky, and know when to use those is even more so. Our industry is FULL of all of the above.
Just fixed a similar issue, what type of SV FF were you in?
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