Story from vision expo on digital centration

**Opticianjw** · 09-26-2011, 02:29 AM

At vision expo west, I was manning a both as a live testimonial for a company that sells dispensing
systems with digital centration. I guy comes up and asks can you Use this system to measure glasses online. So, I tell him no, in conversation he tells me he has a couple of stores and an online optical
Site. He tells me when he sells glasses online he gives everyone a standard pd for the frame size and make all the heights for progressive lenses 4 above. Although he only gets a small
percentage back he feels most see well enough using standard default calculation. I strongly disagreed but was not going to try and argue with him and I let him move on. A few minutes later a women
comes by and looks at the system and tells me that she only sells digital lenses and proclaims that
she feels her customers only want the best products available. I then explain to her that if she is
giving digital lenses and not taking the additional measurements ( face form, rear vertex distance, and panto angle ) than they are really not getting true personallized lenses. Your lab is just using default
calculations and only when those default calculation coincidently mirror the patients real values,does
that patient really get there value when ordering Personalized lenses. I then explained the story
above and the similarities in using default values, she then purchased the system.

**bigeyejim** · 09-26-2011, 10:02 AM

Thank you so much for this story, JW. That my friends is what will keep us all in business. Offering and providing the BEST that we can.

I would bet you that this gentleman who had the online option doesn't really give a crap about his brick and mortar customers as well. Give 'em all a 59!

**Barry Santini** · 09-26-2011, 11:41 AM

I cornered Smart Mirror at expo.

Discovered that a One pixel mir-registration on the camera = 0.2mm. They allow for a 2 pixel misregistration tolernace in the photo-taking, so the PD/repeatability tolerance is plus or minus 0.4mm...which is close to a properly-calibrated and used pupilometer (0.5mm)

Good to know.

Head cape, however, is another story.

More to follow

B

**Java99** · 09-26-2011, 07:18 PM

I also looked at dispensing systems at Expo. One of the companies measured my husband in his POF (rx in the -6.00 sph -2.00 cyl range.) His PD came back 34/29 according to the machine. Wrong. I asked the salesman about it. He said the machine got a negative panto reading and that's why it was wrong. I asked if the lenses in the frame could have caused the problem, the way they bend light and all. Salesman said no, that can't happen. He did not offer to remeasure or explain. I thanked him for his time and walked away.

**Opticianjw** · 09-26-2011, 08:18 PM

I can't speak for other products that do digital centration but I worked the optikam booth and the measurements that
were taken were extremely accurate. I have been an optician for 25 years and I was impressed. In fact the glare from
being at an expo is terrible and even with the lenses being dirty from being handled so much, I was surprised the results were so accurate. In an office setting the results should be more accurate than taking measurements the traditional way with a marker, pd stick and a pupilometer, plus the additional measurements that are needed for digital lenses are much more precise when taken with this technology.

**optical24/7** · 09-27-2011, 09:24 AM

Rx lenses in frame do make a difference in results, lenses (rx) need to come out prior to measuring.

**Barry Santini** · 09-27-2011, 11:17 AM

For all the digital-centration systems, it would be nice to know their expected/stated tolerance for their various measurements. I for one still had some issues with how the frame reference device obtains the pantoscopic tilt reading. On the smart mirror, it seemed to vary in value with head tilt...in my mind, this is incorrect.

Discussion?

B

**Optician1960** · 09-27-2011, 02:05 PM

24/7, right on the money, take Rx lenses out of the frame. My guess is that if the person being measured does not have a 5mm diff in their pd as you said the results came up with, then there may have been either a head turn right or left "or" the frame was sitting closer to one eye than the other.

**Opticianjw** · 09-27-2011, 05:27 PM

I can only speak for the optikam, to avoid parallax the system has a detection system, when the head is turned to either side an arrow comes up notifying you that the head is not in proper alignment. As for the rear vertex distance, this is the
Only system I know that takes an accurate measurement with one front view picture. It eliminates the problems that
occur when taking a second profile picture. The wider temples restrict Being able to take a profile pictures.

**optical24/7** · 09-27-2011, 06:03 PM

Originally Posted by Barry Santini

... I for one still had some issues with how the frame reference device obtains the pantoscopic tilt reading. On the smart mirror, it seemed to vary in value with head tilt...in my mind, this is incorrect.

Discussion?

B

I agree. In relation to ERC, panto is the same biometrically. Held tilt view is not different than off axis viewing. If POW enhanced designs do as expected mis-read panto's will result in mis-calculated cyl/axis compensation.

**Barry Santini** · 09-28-2011, 10:24 AM

For all the advocates of accuracy and precision ascribed to these various digital centration units, it appears that most ecps in these camps substantiate their feelings of accuracy by saying "I know my PD, and these readings are RIGHT ON!"

My question is: "What has been your (previous) gold standard for "knowing" that a device's newly-tendered PD is....correct or right on?"

Follow up: "And why aren't you still using this device as standard?"

I think we're all getting too ramped-up by new-fangled technology. I really want a digital centration system to be fascile, precise and accurate. To that end, I'm gonna take a involved look at the Optikam, thanks to a offer I rec'd from a fellow ECP in New Jersey.

Will advise.

B

**Nikolay Angelov** · 09-28-2011, 11:01 AM

For Barry Santini

:

You can check out the study conducted by Dr Wolfgang Wesemann, he examines repeatability and accuracy of different measurement methods/devices.

Here are the PDF versions:

The harder to find Part 1 of the study:
Comparison of PD measuring devices, Part 1
http://www.hfak.de/download/Wesemann...ices 2010k.pdf

Comparison of PD measuring devices, Part 2
http://www.opticianonline.net/assets...px?ItemID=3966

PS:
The tolerances/accuracy is given at the end of the manual for the Rodenstock's ImpressionIST.
I can check an post them if you would like.

**Barry Santini** · 09-28-2011, 11:16 AM

Originally Posted by Nikolay Angelov

For Barry Santini

:

You can check out the study conducted by Dr Wolfgang Wesemann, he examines repeatability and accuracy of different measurement methods/devices.

Here are the PDF versions:

The harder to find Part 1 of the study:
Comparison of PD measuring devices, Part 1
http://www.hfak.de/download/Wesemann...ices 2010k.pdf

Comparison of PD measuring devices, Part 2
http://www.opticianonline.net/assets...px?ItemID=3966

PS:
The tolerances/accuracy is given at the end of the manual for the Rodenstock's ImpressionIST.
I can check an post them if you would like.

Thank you. I already have a copy of this study. Please refer to the end, where (I'm paraphrasing here) the authior suggests that

"when in doubt, verify with manual method."

So much for vaulted accuracy of DCU.

B

**Opticianjw** · 09-28-2011, 08:13 PM

Barry,
I look forward to meeting with you and letting you see the accuracy and ease of the optikam. Let me know when you are available and I will clear my schedule. As far as answering some of the questions above. Prescription lenses should be removed but not alway necessary. Prism Rx'S and higher prescriptions should be always removed. The Optikam system and I believe all electronic centration systems capture the pantoscopic angle which takes into account the angle of the frame as well as the posture of the patient. It is important as if a frame has a certain pantoscopic tilt, and the patient wears it with his chin down or up, that posture has to be taken into account in addition to the angle of the frame.

**optical24/7** · 09-29-2011, 07:26 AM

Originally Posted by Opticianjw

.. The Optikam system and I believe all electronic centration systems capture the pantoscopic angle which takes into account the angle of the frame as well as the posture of the patient. It is important as if a frame has a certain pantoscopic tilt, and the patient wears it with his chin down or up, that posture has to be taken into account in addition to the angle of the frame.

Head tilt needs to be taken into account for PAL/OC placement, but aren't panto measurements related to ERC? Head up or down doesn't change the relationship of panto to ERC. If POW enhanced lens designs work as intended, this would be the correct calculation to use. Head up/down is no different than off axis viewing. i.e. a retro fit doesn't turn into a panto fit (in relation to ERC) because someone holds their chin down.

**Barry Santini** · 09-29-2011, 08:06 AM

It is important not to confuse the vertical placement of MRPs (SV or Prog), using postural and normal eye depression considerations, with those that dictate how a lens's design/optical axis interesects the eye's center of rotation.

These are two different and iterative fitting considerations.

B

**Java99** · 09-30-2011, 03:36 PM

Originally Posted by Opticianjw

I can't speak for other products that do digital centration but I worked the optikam booth and the measurements that
were taken were extremely accurate.

I was also impressed at the Optikam booth.

**Barry Santini** · 10-06-2011, 05:07 PM

Spent quite a bit of time with an Optikam on the Hoya FF tour. Its clear to me that it can obtain pantscopic angle accurately and independently from a person's head posture, when used properly.*
Good to know.

*properly = informed operator, aka * not * 3 Mile Island

B

**harriseyes** · 09-05-2012, 08:18 PM

In Spring of 2011 I purchased an ABS smart mirror measuring device. I traded in a smart mirror. I asked that the measuring device be set for
three feet instead of six feet b/c of the size of our dispensary. It was delivered but it has never taken accurate pupil heights. I have e-mailed
and called ABS and only once did they respond saying they would need to order me a new unit. I have not been able to contact them since
that e-mail. They will not e-mail me or talk to me about the problem? Does anyone have any suggestions?

Thank you,
Tom

**MakeOptics** · 09-05-2012, 09:01 PM

I use a plumb device from Zeiss (Blue metal device) to take panto measurements. I have the patient tilt there head back with the frames on until their brow and check bones are perpendicular to the ground, then take the measurements on the frame. I also mark up the lenses with the patient looking directly forward while in that positions to mark where the PRP should be, I then compensate the tilt 2 degrees for every mm the PRP is above or below the optimal PRP. This has always worked well for me and provided accurate results. The fitting point is measured while the patient is looking straight forward and incorporates postural preferences. Wrap angle I use a protractor from the back of the Zeiss cut out chart for.

**Barry Santini** · 09-05-2012, 09:14 PM

I must say that trying to quantify "normal" head posture/tilt by asking the patient to "look ahead" and relax is analagous to taking a snapshot picture,and trying to infer what the "movie" is all about. I think Robert Martelaro woud agree that an experienced and trained optician's eye summarizes this elusive parameter better than most digital centration units can.

B

**Darryl Meister** · 09-08-2012, 02:12 PM

I must say that trying to quantify "normal" head posture/tilt by asking the patient to "look ahead" and relax is analagous to taking a snapshot picture,and trying to infer what the "movie" is all about. I think Robert Martelaro woud agree that an experienced and trained optician's eye summarizes this elusive parameter better than most digital centration units can

Keep in mind that pantoscopic frame tilt isn't really independent of head tilt. Although the tilt of the frame is obviously fixed with respect to the head, the tilt of the frame with respect to the line of sight is not. Consequently, any habitual (or even unwanted) head tilt will influence the angle that the frame front makes with the line of sight in primary (straight-ahead) gaze.

For the purposes of calculating the optics of a lens inside the frame, the tilt of the frame relative to the line of sight in primary gaze must be measured. Since the fitting points of progressive and customized lenses should intercept the lines of sight in primary gaze, the proper measurement of pantoscopic tilt is captured when the orientation of the head is equal to the orientation used to measure the fitting heights. This is most easily accomplished when the tilt of the frame is measured at the same time or position as the fitting height measurements.

If the orientation of the head during the fitting height measurements is equal to the orientation during the other position of wear measurements, the planes should be properly calculated based upon the intersection of each line of sight with the intended fitting point of the lens, which will yield the correct optical calculations. So any habitual head tilt will not negatively influence the pantoscopic tilt measurement, although unwanted head tilt may negatively influence the actual fitting height measurements.

Best regards,
Darryl

**Barry Santini** · 09-08-2012, 04:25 PM

Originally Posted by darryl meister

keep in mind that pantoscopic frame tilt isn't really independent of head tilt. Although the tilt of the frame is obviously fixed with respect to the head, the tilt of the frame with respect to the line of sight is not. Consequently, any habitual (or even unwanted) head tilt will influence the angle that the frame front makes with the line of sight in primary (straight-ahead) gaze.

For the purposes of calculating the optics of a lens inside the frame, the tilt of the frame relative to the line of sight in primary gaze must be measured. Since the fitting points of progressive and customized lenses should intercept the lines of sight in primary gaze, the proper measurement of pantoscopic tilt is captured when the orientation of the head is equal to the orientation used to measure the fitting heights. This is most easily accomplished when the tilt of the frame is measured at the same time or position as the fitting height measurements.

If the orientation of the head during the fitting height measurements is equal to the orientation during the other position of wear measurements, the planes should be properly calculated based upon the intersection of each line of sight with the intended fitting point of the lens, which will yield the correct optical calculations. So any habitual head tilt will not negatively influence the pantoscopic tilt measurement, although unwanted head tilt may negatively influence the actual fitting height measurements.

Best regards,
darryl

Yessssss!!!!!

B