Never see a thing like this before here. anyhow, currently what we using now is something similar from essilor.
The specs for this pupilometer are terrific for initiating a discussion of the assumed accuracy & precision of taking pupillary measurements.
Below are listed the possible errors affecting accuracy, as I see it. Please chime in with any comments or thoughts.
1. Indication error
2. Rounding error
3. Parallax error:
a. Operator not holder pupilometer "correctly"
b. Physiological error -
i. forehead/browbone contour of client not representative of eyeplane
ii. Nasal bone contact point of pupilometer inconsistent with the eyewear's actual fitting position.
4. Calibration error - seems similar to indication error, but actually is different.
Let's look at a worse-case scenario:
Indication error 0.5mm + rounding error 0.5mm + operator error 0.5mm + physiological error 0.5mm + calibration error 0.5mm
Total 2.5mm possible monocularly!
Seems to negate our industry's arguement about how PDs would be taken from an uploaded photo.
But wait, come to think of it, if the facial plane in an uploaded photo was ensured to be orthogonal, i.e., "square-up", I thinking that, with a known size reference in the same photo, (perhaps a dime), one could postulate that, indeed, uploaded photos have the capability *of* being more accurate than conventional pupilometer readings made in person.
I think that the method used by Feinbloom for their surgical telescopes, which is completely *subjective*, is the only really accurate way to obtain PDs.
Thoughts? Discussion.
Harry, shoot me down here, will you? I like goin' down in "flames":hammer:
Barry
Last edited by Barry Santini; 07-10-2009 at 09:15 AM.
A picture up-loaded to the internet can not accurately;
1. Represent how eyewear will sit on a patients nose. You can't superimpose a frame on someone's face and correctly judge if the frame will shift horizontally or vertically.
2. Accurately account for nasal bone misalignment. This will hinder an accurate monocular measurement
3. Determine panto, vertex, wrap, ect.
4. Determine fixation point. ( what is the patient looking at while the picture is taken? How far away is their fixation point?)
5. Determine posture.
6. Determine stature.
7. Take a specific pupilary measurements of near/intermediate.
imho...
Agreed!
But...by & large, how many pairs of eyewear are fitted with this degree of care and competance? I think this is why a statement from framesdirect.com saying it's "...more accurate..." may in fact, be true, when compared with how it's all done in the majority of cases.
Certainly, optical24/7, *any* pupilometer will *not* factor in any of the important things you've cited.
Yet, on the other hand, considering so many pairs of eyewear are *not* measured and fitted in the manner suggested, it's surprising how many people are apparently "satisfied" with their eyewear.
Perhaps herein lies the secret of the internet's potential market success.
Keep it goin'....
Barry
How many of us have:
1: Measured the monocular P.D. with a ruler?
2: Measured the monocular P.D. with a pupillary reflective device?
3: Measured the marks on a "dotted-up" frame?
Done this in significant numbers on the same patients (all three for each patient). And compared the results for deviation?
I haven't and I suspect few if any of us have.
I did on one occasion have a group of 35 or so patient's that I measured with a pupillary reflective device. While a co-worker measured a similar amount of patients with a ruler.
When the patient's returned to pick-up spectales we did not find over 1 mm. difference between his measurments and mine. I might mention that while we were both journeymen opticians, it was my first day to use a pupillary reflection device.
Chip
Chip
Has anyone answered the original question?
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