Current ANSI stds. for sphere & cyl

[eyevay]

Does anybody know the official latest ANSI tolerances for sphere & cyl powers? I'm about to take my state license exam & I seem to have conflicting info about which is the latest version (1987? 1995? 1999? etc.). Are they stated in diopters or percentages?

If anybody knows this info, it would be greatly appreciated if you could post a simple table/chart/list in your reply. I can't afford to buy the whole darn document & you would think this should be public information available on the web!

thanks muchly!

[eyeguy2002]

Eyevay..here it is-

For the sphere component from 0.00 to +/-6.50D tolerance +/-0.13D.....above +/-6.50D tolerance +/-2% of the sphere power.

For the cylinder component from 0.00 to 2.00D cyl tolerance+/-.13 D.....from 2.12D to 4.50D cyl tolerance +/-0.15D and above 4.50D cyl tolerance is 4% of the cylinder power...

Hope this is what you looking for...anybody else help?

eyeguy2002


:cheers:

[eyevay]

:D eyeguy--

Thanks, that was fast! Just what the doctor (woops, I mean LDO) ordered!

[JRS]

You should also note word changes in the 1999 version - "absolute power of meridian of highest power". This would mean that a -6.00 -1.00 @ axis, falls in the 2% catagory. Not in the +/- 0.13 column.

[Kevin Howtopat]

ok then. so, for example, If I had an Rx that was -2.50 -1.00 x180 and the lens actually read -2.62 -1.12 x180, this would still be within tolerance ? Even though the total power is off by .25D? (this would be unacceptable where I work)

[JRS]

NO! The lens is off power! The power through the highest meridian exceeds +/- 0.13 diopters.

However, if it read -2.37 -1.12, it would be in tolerance.

[eyevay]

does the 1999 wording affect changes in cyl tolerances also?

and what about unwanted-prism tolerances? I've heard tell that now they tolerate 1/2 a prism diopter for vertical imbalance rather than the 1/3 it has been. though as far as I know, the
tolerance for variation in OC height is still only 1mm...

if anyone knows of any other significant changes, it would be good to know, esp. before my exam Thursday!