New Axis Tolerances

[jherman]

I just found this and thought it might be news to others also.:D


.12,.37=14 degrees
.50 7 "
.50.75 5
.75,1.50 3
over1.5 2

My copy of the tolerances shows an overlap at .50, not a typo.

[Andrew Weiss]

James, it's news to me. Are these new ANSI standards? Can you tell us where you found them published?

It looks like we're being encouraged to be sloppier rather than more precise. Isn't this moving things backwards?

[Jacqui]

Those are rediculous. We use:

0.12 - 0.5 = 3 degrees
0.62 - 1.00 = 2 degrees
1.00 and higher = 1 degree

Yes we hold these. These are pretty much the old AOA standards that I grew up with.

[Andrew Weiss]

Those are rediculous. We use:

0.12 - 0.5 = 3 degrees
0.62 - 1.00 = 2 degrees
1.00 and higher = 1 degree

Yes we hold these. These are pretty much the old AOA standards that I grew up with.

You and I must be from the same generation :)

[jherman]

nm

[Andrew Weiss]

nm

James, I tried the url in the title to your last message and Firefox could not find it. What gives?

[Jacqui]

You and I must be from the same generation :)

I think these kids with their high-tech equipment are getting lazy.

[Jacqui]

James, I tried the url in the title to your last message and Firefox could not find it. What gives?

Google and MSN couldn't find it either

[jherman]

www.opticallabproducts.com

James, I tried the url in the title to your last message and Firefox could not find it. What gives?

[AWTECH]

new ANSI standards, do not mean you have to make every lens this far off specifications, it is a minimum standard. A lab could offer much tighter standards if they choose.

I believe this change was driven by the lack of accuracy available to each Rx for PALs. Most PALs are a compromise based on the semi-finished blanks. These as you know combine a fixed near and far ratio lens surface, usually limited to about 65 blanks.

Here is a link to an article relating to this subject.

http://www.opticallabproducts.com/15/tech_setting.php

I think these tolorances would be able to be held more accurately if there are 2 million plus Rx lens designs available to exactly match each prescription. Freeform offers tremendous improvements in accuracy when incorporated with great lens designs. Just the difference in variation between fining and polishing a spherical cut lens vs. a freeform lens of the same spherical curve can vary. The freeform version can be accurately repeated. The spherical cut with laps and fining and polishing will not be as accurate as multiple freeform lens made with the same spherical cut.

[chip anderson]

Remember that ANSI standards are the sloppiest you are allowed to do. The best tolerance is 0. I have also read that if criticly inspected only 25% of glasses sold in the U.S. would pass even ANSI standards.


Chip

[fjpod]

It's really tough to nail a .25 cyl axis on a progressive. We did a little test at our office using a manual lensometer and a Tomey autolensometer. Three ODs and three LDOs used the manual lensometer and got more variability than three benchmen using the autolensometer.

Forget fabricating and finishing the darn thing...just reading it is fraught with likely variability.

[RT]

http://www.optiboard.com/forums/showthread.php?t=15683

[fjpod]

http://www.optiboard.com/forums/showthread.php?t=15683

The link kind of "proves" what I said about the variability in measurement of .25 cyls. ESPECIALLY on progressives.

I haven't met a patient yet, who on a subjective refraction could give consistent responses on a fan dial or JCC when they had a .25 cyl...not on cyl power or axis. Yes, sometimes they will say the .25 cyl is better...but they will say this whether you put it in at 160, 170, 180 or 010 or 20. (presumed axis 180).

[David Wilson]

[QUOTE=Jacqui]Those are rediculous. QUOTE]

Not really. They may seem ridiculous but only because they don't agree with our perceptions of what is correct. Have a look at the article written by Darryl Meister in the Optiboard File Directory. It explains all.

http://www.optiboard.com/forums/showthread.php?t=15683

Regards
David Wilson

[Jacqui]

[QUOTE=David Wilson]

Those are rediculous. QUOTE]

Not really. They may seem ridiculous but only because they don't agree with our perceptions of what is correct. Have a look at the article written by Darryl Meister in the Optiboard File Directory. It explains all.

http://www.optiboard.com/forums/showthread.php?t=15683

Regards
David Wilson

Still won't let my patients wear something that far off.

[Darryl Meister]

Still won't let my patients wear something that far off.

At the end of the day, the ANSI Z80.1 standards are only recommended guidelines, and you are certainly free to strive for tighter tolerances. While 14 degrees is certainly justifiable from a visual and optical standpoint, I personally would have preferred something closer to, say, 9 degrees -- mainly because it represents a small yet adequate step in the right direction. However, these decisions are made as a committee, and the group decided to adhere to a consistent methodology for all of the cylinder axis tolerances. Frankly, you are unlikely to see a 0.25 D cyl that far off, anyway.

[Darryl Meister]

My copy of the tolerances shows an overlap at .50, not a typo.

Also, there's no overlap at 0.50 D; it's 7 degrees for 0.50 D, and 5 degrees for anything above 0.50 D up to and including 0.75 D.

[jherman]

It states I can be off 7 or 5 on .50 cyl, and 5 or 3 on a 3 75cyl?

Wonder why they didn't continue in 1/8 steps?

Also, there's no overlap at 0.50 D; it's 7 degrees for 0.50 D, and 5 degrees for anything above 0.50 D up to and including 0.75 D.

[Darryl Meister]

It states I can be off 7 or 5 on .50 cyl, and 5 or 3 on a 3 75cyl?

I can't vouch for whatever you're looking at, but the actual standard in fact reads:

> 0.00 D
≤ 0.25 D
± 14°

> 0.25 D
≤ 0.50 D
± 7°

> 0.50 D
≤ 0.75 D
± 5°

> 0.75 D
≤ 1.50 D
± 3°

> 1.50 D
± 2°

[Cherry Optical]

Those are rediculous. We use:

0.12 - 0.5 = 3 degrees
0.62 - 1.00 = 2 degrees
1.00 and higher = 1 degree

Yes we hold these. These are pretty much the old AOA standards that I grew up with.

They are both rediculous. We use:

0.01 - 0.50 = 0.000000000001 degree
0.51 - 1.00 = 0.000000000000001 degree
1.01 an higher = 0.0000000000000000000000000001 degree

We had to use a laser to add a few trillion lines to our axis wheels... but boy has it paid off!

::yawn:: sorry for the smartdonkey response, long day... and it's not even close to over. Perhaps the folks that should give some insight into the changes is someone from the ANSI group that can explain how prescriping a 0.25 cylinder is a bit of a subjective finding.

Adam

[Cherry Optical]

Remember that ANSI standards are the sloppiest you are allowed to do. The best tolerance is 0. I have also read that if criticly inspected only 25% of glasses sold in the U.S. would pass even ANSI standards.


Chip

I read the same thing. Interestingly enough I believe I remember reading that if criticaly inspected, only 24% of the glasses sold in the rest of the world (outside the US) would pass ANSI standards. Infact, I also read that glasses manufacturered in China pass ANSI standards, but after about 6 weeks of use they fall apart, and thus fail to pass the standards.

Adam

[Darryl Meister]

Perhaps the folks that should give some insight into the changes is someone from the ANSI group that can explain how prescriping a 0.25 cylinder is a bit of a subjective finding

It's all explained in that memo cited earlier.

[Cherry Optical]

It's all explained in that memo cited earlier.

That would involve reading........

Adam

[jherman]

for holding my hand through that one Darryl.

I can't vouch for whatever you're looking at, but the actual standard in fact reads:

> 0.00 D
≤ 0.25 D
± 14°

> 0.25 D
≤ 0.50 D
± 7°

> 0.50 D
≤ 0.75 D
± 5°

> 0.75 D
≤ 1.50 D
± 3°

> 1.50 D
± 2°