Please dont laugh at me!

[LENNY]

I was at my friends shop today and played with his Kappa edger.
What I noticed is the blocker measures the height of bifocal segment directly from the center of bifocal line to the eyewear rim dirrectly bellow it.
I think when I went to school we used to measure the bifocal height to the lowest point of the eyewire!? My friend told me that he always measure bifocal height directly under pupil to the eyewire. And this is how his machine cuts!
I am surprised?
Please help!

[Jason Carruthers]

Lenny


You use the "box method" of measurement which I believe is the newer and more standard method.

As far as I am concerned, you are right and the Kappa is wrong.

[DocInChina]

Lenny, your way is the correct way of taking measurements. However, some people do take measurements in the same manner as your friend. As long as all the work is being done internally then your friend will have no problem. If he were to order Rx lenses from his lab, I would be surprised if he didn't have a problem some of the time with the lenses he receives.

Doc

[Spexvet]

What I noticed is the blocker measures the height of bifocal segment directly from the center of bifocal line to the eyewear rim dirrectly bellow it.
Please dont laugh at me!

Hahahahahahahahaha (sorry, couldn't help myself :p ). DocinChina is correct, and so are you. Your lab probably sent you instructions, as mine did, that tells you the system they use. Check - it's very likely that they use the "seg line to lowest point in the frame" method.
:cheers:

[shanbaum]

I was at my friends shop today and played with his Kappa edger.
What I noticed is the blocker measures the height of bifocal segment directly from the center of bifocal line to the eyewear rim dirrectly bellow it.
I think when I went to school we used to measure the bifocal height to the lowest point of the eyewire!? My friend told me that he always measure bifocal height directly under pupil to the eyewire. And this is how his machine cuts!
I am surprised?
Please help!

There may be a setting on the Kappa that causes it to express the seg height the way you describe (center of seg down to eyewire), because a lot of Brits and some Aussies insist on doing it this way. It is indeed a preposterous way to do it; without a tracing, the number is meaningless.

And the Kappa most definitely can be set to express heights according to the boxing method with which everyone (else) is familiar.

[LENNY]

Thanks!

I thought I was loooooossssisnnnnngggg it!

[Johns]

You may be losing it, but I agree w/ your method as well.

[LENNY]

So we ARE loosing it together!

[David Wilson]

There may be a setting on the Kappa that causes it to express the seg height the way you describe (center of seg down to eyewire), because a lot of Brits and some Aussies insist on doing it this way. It is indeed a preposterous way to do it; without a tracing, the number is meaningless.

And the Kappa most definitely can be set to express heights according to the boxing method with which everyone (else) is familiar.

Robert is right, some Aussies do use this method, and I agree with Robert's views on it. We are trying to convert those who have strayed from the path. and you can be sure it is not taught that way in their course.

Regards
David

[Trevor D]

Seg heights

Robert is right, some Aussies do use this method, and I agree with Robert's views on it. We are trying to convert those who have strayed from the path. and you can be sure it is not taught that way in their course.

David why is that? Every "younger" dispenser i've worked with or for does it this way. They all tell me I'm wrong to measure from the lowest part of the frame and not the PD. I show them the textbook but I never convert them. What happens when you get an aviator frame and different mono pd's? You will end up with differing segment heights. My previous manager avoided the debate with me about it and hated listening to alternate points of view. Besides, he never took a mono PD regardless of Rx or lens type.... :finger:

[Chris Ryser]

Dead Wroong..................

So we ARE loosing it together!

No Lenny, you are ALL right..................

[Darryl Meister]

I think the most obvious problem with the British approach is that there is no simple way of determining how far to drop the segment from the geometric center of the former / pattern for blocking and edging purposes (at least without a template of some sort, as Robert pointed out). It also makes it more difficult to verify the segment height (at least without spotting the PD first), since you have no fixed lower reference point. Their system of calculating decentration was equally confusing, though I guess they could at least cut their patterns differently (at the "datum" center instead of the more common geometric center) to compensate for this particular issue.

[Darryl Meister]

Ps

It's also interesting to note that, in spite of the obvious inconsistencies of the British system, they actually had required a 0.5 mm tolerance on segment height, versus the 1.0 mm tolerance that we've been using in the US.

[JRS]

I think that was called the "Datum" method. And if I recall there was also a "British" method that related more to the "Datum" than to the "Box" system. Still have some old text books that describe measuring at 180 for the horizontal and straight down (under eye) for vertical. Included the British way too. I thought it had gone. However, as Robert noted, the machine could be quite capable of units either way. Sold in both US and abroad.

[Darryl Meister]

I think that was called the "Datum" method

Yep. I'm not sure whether they still use it though.