Go!
Me: Ahhh...no.
Why? Because. 0.5mm is about as precise as one could need.
Now accuracy. That's another subject.
I'd again caution ECPs from overplaying the importance of their metric of a traditional PD. Storm's a coming.
B
Go!
Me: Ahhh...no.
Why? Because. 0.5mm is about as precise as one could need.
Now accuracy. That's another subject.
I'd again caution ECPs from overplaying the importance of their metric of a traditional PD. Storm's a coming.
B
Over the years I've seen the old timers through a PD stick up to a PT nose for about a second and a half , wright down a PD and move on . Never did a PT come back with a PD issue .Originally Posted by Barry Santini
In PAL's yes (precision perhaps needs to be defined)
The adaptability of humans is sometimes intriguing. I have seen many a pair off by multiples of mm. that pat's. have been satisfied with.
Perhaps precision lies in the hands of the person doing the measurement, not the measurement in and of itself. A PD of 60 may be correct but a skilled (accurate) optician would be able to see that in all actuality the PD should be 31/29?
Clinton Tower
The intellect to live free is in short supply
ALT248=°
accuracy - the ability to hit a target where you intend
precision - the ability to hit a target where you intend multiple times
just wanted to clear that up. Ansi has all the answers. Can you tolerate tolerance? Most can. Some cant. You need to bullseye some patients. Theres black and white lines on this one B. I love the topics.....Keeps the mind sharp on dull days. Thanks!
+1
1/2 mm. 1/8 diopter. Good to go. The human eye usually can't tell a difference beyond that. Thus ANSI standards.
exact PD is about as important as an expired plano rx
Barry,
You are just having too much fun stirring the pot these days! Keep it up.
So no, absolute precision isn't the final answer, but the ATTEMPT at getting as accurate an answer should be the goal. Set the bar higher, you'll end up with a better fighting chance at an excellent result. Allow too much variation from precise and you'll get bland and average.
I've seen the arguments over digital lenses, extra measurements, whether one can tell if a compensated rx is really necessary... The naysayers may be correct on one level, but if one strives for more accurate measurements, better placement, more precise rx's, then you'll get better results. Some think that it is overkill since the patient cannot discern the difference between -3.25 and -3.37. A PD of 30.5/31.5 instead of 31/31? True, most won't notice such a slight difference, but it surely can't hurt to start off with more accurate measurements.
Barry, I think that conventional wisdom might support the notion of you finding a hobby more suitable, like drinking. One can only image the threads posted. The question that resonates is, will it be precision or accuracy that you employ to facilitate full inebriation. I prefer accuracy to precision, for IPD measurements and drinking.
I didn't attend the funeral, but I sent a nice letter saying I approved of it. Mark Twain
But my measurements are accurate to a tenth of a millimeter!!!!! What are you saying!!!!!!
Can't count the number of times I've had rejects come back only to find out the "optician" did not mark-up the PAL precisely when inspecting the finished pair. I really love it when they use a 4mm chart on a 2mm PAL (that's MRP to PRP "drop").
Clinton Tower
The intellect to live free is in short supply
ALT248=°
"I really love it when they use a 4mm chart on a 2mm PAL (that's MRP to PRP "drop")."
Why do basically all manufacturers agree that there is 34 mm between the progressive markings (with the add power under the temporal marking and index under the nasal) but they can't agree on a uniform fitting cross height of say 2 mm above?
+1.))
The other component for many to remember, is that you're only one part of a chain. If the doc's subjective happens to be off by just that little bit, and the dispenser measures PD/OC/Seg off just a little bit, and the guy doing the layout is off just a little bit, and the power comes back from the generator off just a little bit, and the edger is off just a little bit, and the frame is out of adjustment just a little bit...
You can end up with a very different final product than what was initially intended. It might still be within ANSI - and it might not.
But for the sake of argument - it seems prudent that we should all, at every stage of ordering and production, attempt the simple task of always being as precise as possible - every time. Whatever metric you want to use to measure that by of course. Does it not?
Good points, Uilleann
Last edited by Barry Santini; 09-13-2014 at 10:58 AM.
Because the 34mm separation between the engravings is an ISO standard, and there's no standard at all for the positioning of the LRP relative to the PRP.
thanks for the explanation.
time for a new iso standard?
+1,Uilleann
Last edited by Gizzo; 09-17-2014 at 07:44 PM. Reason: incomplete
YES!!!!
Now, I agree with Barry that 0.50mm is probably as precise as we may need to be, give most people's ability, or lack thereof, to notice anything more precise.
However, if you can be more precise, then why not?
Personally, I would prefer to be as precise as I possibly could be, simply because I knew I did the absolute best for the patient that I could, whether that particular patient could actually tell the difference or not.
Of course this then leads to those cases where the patient's pd is 60, and their glasses have been made 30/30 for years, but their pd is really 28/32, so when they're made "right," the patient can't see...
So, always check, whenever possible, what the patient is currently wearing compared to what you measured, and if at all possible, trial frame with both the new Rx and "new" pd to see if there is any immediately noticeable difference. But you all already knew that didn't you.
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.
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