Current ANSI Cheat Sheet

[John@OWDC]

Does anyone have a copy of the CURRENT basic ANSI stuff?
Sphere, cylinder, axis, etc?
Just that basic cheat sheet most stores have up next to the lensmeter.
I need to start memorizing them for an upcoming practical.
Thanks
John

[bretk0923]

https://www.thevisioncouncil.org/sit...rence%20v2.pdf

As far as I'm aware, this is still the most current list.

[John@OWDC]

Thank You!

[Oscar]

can someone help me understand PD tolerance? When I was taught, if was a function of induced prism based on prentice's rule. Once you got over 2.50D the amount of prism induced even at 1mm would not be acceptable. However looking at the chart now, it allows 2.5mm over 2.75 diopters?!!?!?! how does this work?

example -4.00 but the pd is off by 2mm. by prentice's rule :
Prism = d x F
prism = 0.2 x 4
prism = 0.80D which does not pass tolerance the way I was taught, but will pass this current one?!?!!

[Oscar]

No one has any input?

[Erik]

Hi folks! I've been lurking on these forums a while. Today I though I'd throw in my 2cents.

That prism imbalance is spread over two eyes so it's actually .4D per eye. IIRC, 2.5mm has been the permissible horizontal tolerance for higher rx's for quite a long time.

[optical24/7]

There's not much to comment on, other than that's the new "recommended" tolerances. It doesn't mean you have to abide by them. Use your own stricter ones. (BTW, horizontal prism is less problematic than vertical prismatic imbalance).

[Oscar]

Hi folks! I've been lurking on these forums a while. Today I though I'd throw in my 2cents.

That prism imbalance is spread over two eyes so it's actually .4D per eye. IIRC, 2.5mm has been the permissible horizontal tolerance for higher rx's for quite a long time.

My example was only for 1 eye so you cannot half that calculation. Is the 2.5mm referencing binocular or monocular?

This was the tolerance chart that I was taught with and is the first result that shows up when you search for Nacor Tolerance Chart. It has since changed to the one linked above.
http://www.nacor.ca/my_folders/For_C...20Handbook.pdf

in particular it mentions which only allows 0.25 per eye.

[Erik]

2.5mm is binocular but can be all in one eye or split between both, as long as the lenses are not PALs.

[dima]

I think is Like this:
For single vision
You have to avoid prism over 0.33 vertical and/or 0.67 horizontal

Even if the prism is less you have to not wrong the position of optical center more than 2.5 mm


Folks am I wrong?

[Oscar]

I think is Like this:
For single vision
You have to avoid prism over 0.33 vertical and/or 0.67 horizontal

Even if the prism is less you have to not wrong the position of optical center more than 2.5 mm


Folks am I wrong?

Yes this is correct. However the current ANSI chart says power over +/-2.75 is allowed up to 2.5mm tolerance. If we did the math that is over 0.67 prism.

[shanbaum]

No, the location of the PRP must be within 1.0mm vertically and 2.5mm laterally, of the location specified, if the prism induced exceeds 0.33 prism diopters (vertically) or 0.67 prism diopters (laterally). For PALs, the lateral positioning tolerance is 1.0mm instead of 2.5mm