OptiCampus Updates

[Darryl Meister]

OptiCampus Updates

Weekend of June 18th:
Finished Spectral Transmittance Charts page in Dispensing Tools: OptiCampus Spectral Transmittance Charts

[Darryl Meister]

Weekend of July 9th
Improved Tilt and Wrap calculator in Dispensing Calculators so that it now calculates both pantoscopic tilt and facial wrap compensation simultaneously: OptiCampus Tilt and Wrap Compensation

[Leo Hadley Jr]

Darryl,

Your site is Outstanding, Could I link it too mine?

[chip anderson]

Damn you smart. I often feel ashamed to call myself an optician after I read your stuff.

Chip:cheers:

[Leo Hadley Jr]

Agreed!!!

There are a lot of members here like that :)

[Darryl Meister]

Could I link it too mine?

You're welcome to add a link to OptiCampus, if that's what you're asking.

I often feel ashamed to call myself an optician after I read your stuff.

Don't underestimate the value of your own skills and expertise, Chip. Besides, it's easy to sound impressive when you become as specialized as I have (in spectacle lenses), though I couldn't fit a contact lens to save my life.

[Darryl Meister]

OptiCampus Updates

Weekend of September 8th:

Finished progressive lens course: Optics of Progressive Lenses

Added a summary of the forthcoming Z80.1-2005 tolerances: ANSI Z80.1-2005 Summary

Added a calculator to compute prism at any point in a lens: Induced Prism Calculation

[lensgrinder]

Darryl,
I just wanted to take the time to tell you how much I enjoy reading the things you post here, your articles that have been posted, and opticampus.com. By reading your things it really makes me think deeper in to problems. So thanks

Brent

[Darryl Meister]

I just wanted to take the time to tell you how much I enjoy reading the things you post here, your articles that have been posted, and opticampus.com

Thanks, Brent. I'm glad you find it useful.

[OPTIDONN]

Sweet!!!:d

[NavyChief]

when did the standards change to allow a 14 degree tolerance for > 0.00 D, ≤ 0.25 D?
I've been using .12 to .37 7 degrees. The 14 degree tolerance was listed in your reference page for OptiCampus ANSI Z80.1-2005 Summary. I never heard of such a wide tolerance. By the way, real nice website at OptiCampus.com. Thanks for your input.
OptiCampus ANSI Z80.1-2005 Summary

[Darryl Meister]

The looser cylinder axis tolerance is new to the 2005 revision. Essentially, the axis tolerance on the lowest Cyls was re-evaulated as a result of frequent misapplication of the standard, particularly during poorly executed "exposes" on the optical industry. However, a large scale study of the process capabilities of modern optical laboratories confirmed that the tolerances on the lowest Cyls were probably unnecessarily strict.

In reality, the axis tolerance on the 0.25 Cyl has always been too tight, and this has been acknowledged since the inception of the Z80.1 standard. Essentially, the axis tolerances were based upon the amount of axis error necessary to produce a power error equal to the cylinder / sphere power tolerance. All of the axis tolerances were more or less based on this rationale, except for the 0.25 D Cyl. (Above a 1.50 D Cyl, you're allowed a minimum tolerance of 2 degrees, which is generally considered to be the limiting tolerance for mechanical alignment throughout the Z80.1 Standard.)

The axis error can be calculated using,

Axis Error = Arcsin[Power Error / (2 * Prescribed Cylinder)]

For a prescribed cylinder power of 0.25 D, and an assumed power error of 0.12 D, the axis error is equal to 13.9 degrees. However, it was felt many years ago that most eyecare practitioners would not understand the optical principles involved, and might question such a tolerance, so an arbitrary figure was chosen instead for the 0.25 D Cyl. As of the latest revision, the Subcommittee more or less decided that this approach was causing more harm than good.

That said, this is really more of an issue with progressive lenses, which for various reasons often show a small amount of cylinder at the distance measurement point. Even when this cylinder is within tolerance (ISO has optical tolerances on progressive lens blanks), it can interact with prescribed cylinder power when it is also low, causing unusual axis shifts. While these shifts are visually inconsequential, they can be an annoyance to deal with, especially when the axis tolerance is theoretically twice as tight as it should be.

[QDO1]

It sounds like the US relaxed the standards because it was shown that the industry was unable to continue to create jobs to the old standard. This happened in the UK a few years ago. The advantage of a high standard, is that if the industry just fails to meet it, the chances are the jobs are still within a patient tollerable limit

It seems to me with deregulation of Dispensing (in the UK) and the switch over from using skilled staff, to robotic equipment in the labs, the quality levels wont be attained, and the people checking the jobs wont know the difference anyway. This is demonstrated by a "lab tech" in a large well known lab in the UK, that I recently visited, telling me that they turn off the "saftey bevel feature" to increase hourly throughput. With low-skilled staff assembling jobs it is hardly surprising that jobs make it out of the lab sharp.

One would think (if you belive the hype) that with all the latest new digital achinery, we could make jobs more accurate than ever before

[Darryl Meister]

It was a combination of process capability and the fact that, for the axis tolerance on the 0.25 D Cyl, the tolerance was tighter than it should have been in the first place. Exposes treating the voluntary "guidelines" of the ANSI Standard as a pass / fail mandate didn't help, either.

[MarkH]

Does anyone have any further information on the ANSI Z80.1-2005 update? Will it become official?

[QDO1]

i subscribe to the theory - aim for the very best, if you just miss, and are within the standards, you are doing ok... this is in oposition of the "aim for the standard" and hope philosophy

[Aarlan]

"It's not good...but it's good enough"
-lab tech I once worked with

AA

[Darryl Meister]

Does anyone have any further information on the ANSI Z80.1-2005 update? Will it become official?

It ran into a hickup or two, but it is now official. I would encourage everyone to purchase a full version of this document from ANSI's eStandards Store, once it has been made available online (probably in January).