Atoric

[April_01]

What does an atoric lens mean?

[shanbaum]

What does an atoric lens mean?

It's a lens which affords two major power meridia, oriented at ninety degrees to one another, each of which is an asphere.

[April_01]

It's a lens which affords two major power meridia, oriented at ninety degrees to one another, each of which is an asphere.

So is it similar to aspheric? Is it a design that you order to a lens material like you would order aspheric to a high plus to make it flatter on the front?

[shanbaum]

So is it similar to aspheric? Is it a design that you order to a lens material like you would order aspheric to a high plus to make it flatter on the front?

Yes. An "atoric" is to an "aspheric" as a "toric" is to a "spheric".

Aspheric lenses typically have aspheric front surfaces and spherical or toric back surfaces.

Augen recently introduced a lens with an atoric front surface, to be used in conjuction with a toric back surface. They assert that this produces better performance than a merely aspheric front.

I believe that most other atores are produced by various free-form (Zeiss, Rodenstock, Shamir) processes.

[April_01]

So who would you recommend an atoric design to?

[shanbaum]

So who would you recommend an atoric design to?

I wouldn't, necessarily, but those who make them would say that they are appropriate whenever an aspheric would be, when the wearer's Rx includes cylinder; the more cylinder, the more appropriate.

[drk]

Shanbaum, see if I'm amplifying your answer correctly:

When an optician wants to recommend a thinner, flatter, lighter lens for a spherical plus Rx or a (somewhat) thinner, lighter lens for a spherical minus Rx, the base curve is substantially flattened from the normal corrected curve and then the lens flattens further towards the periphery, in order to compensate for the abberation induced by using a flatter base curve than the corrected curve.

In a spherocylinder Rx, the flattening towards the periphery of the lens in an atoric lens is different for both principal meridia, compensating for abberration better than if just a asphere was used for a spherocylinder.

Bottom line: when making a thinner, flatter lens, aspheric compensation is needed for a sphere and atoric compensation is needed for a spherocylinder, if you want to do it right.

The catch: atoric lenses are rare. Your choices are Sola's Vizio 1.66, and presumably Optima's Resolution polycarbonate.

[shanbaum]

Shanbaum, see if I'm amplifying your answer correctly:

When an optician wants to recommend a thinner, flatter, lighter lens for a spherical plus Rx or a (somewhat) thinner, lighter lens for a spherical minus Rx, the base curve is substantially flattened from the normal corrected curve and then the lens flattens further towards the periphery, in order to compensate for the abberation induced by using a flatter base curve than the corrected curve.

Close - typically, an aspheric lens for minus Rx's gets steeper towards the periphery, and the base curve itself is no steeper than usual - for minus lenses.

[drk]

DOH! I knew that. I was given the visual picture that the aspheric minus front surface is like a "Frisbee", I just forgot.

[shanbaum]

DOH! I knew that. I was given the visual picture that the aspheric minus front surface is like a "Frisbee", I just forgot.

Minus, oblate; plus, prolate.

[drk]

Nice!

[chip anderson]

Aspheric: Not a sphere

Atoric: Not a toric (torus)

Technically a lens in which one curve becomes longer or shorter in radius in the case of aspheres, Two or more curves become longer or shorter in radius in atorics.

Chip

Sola has an hour or two you can get credit for listening to on the subject of atorics.

[Darryl Meister]

Here is an article I wrote on the atoric lenses:
Principles of Atoric Lens Design

Best regards,
Darryl

[F.Bourreau]

Hello,

how can i get this artical.... i try to click on the link but .....

Fred

[eromitlab]

now... this has been a question that has been bugging me for the past couple of days (was actually re-reading Darryl's aforementioned article at the time it popped into my head), is "Double-Aspheric" the same as "Atoric?"

I believe the answer is no based on what Darryl described in his article as atoric lenses being "optimized" for the power that is manufactured into it... thus making it only a finished lens option for pretty much anyone right now, but I've been running Double Aspheric lenses in the lab for some time now with conventional equipment. Am I wrong in my assuptions and what differences are there between the two?

[Steve Machol]

Hello,

how can i get this artical.... i try to click on the link but .....

Fred

I gave you a direct link to that article in your other thead:

http://www.optiboard.com/files/Asphe...plications.pdf

I had to disable the file database program I was using because of the recent PHP security exploits.

[shanbaum]

now... this has been a question that has been bugging me for the past couple of days (was actually re-reading Darryl's aforementioned article at the time it popped into my head), is "Double-Aspheric" the same as "Atoric?"

I believe the answer is no based on what Darryl described in his article as atoric lenses being "optimized" for the power that is manufactured into it... thus making it only a finished lens option for pretty much anyone right now, but I've been running Double Aspheric lenses in the lab for some time now with conventional equipment. Am I wrong in my assuptions and what differences are there between the two?

The Double Aspherics are indeed atorics. The atoricity is simply "optimized" for a range of cylinder powers, rather than for a single power... which is to say, it's not quite so optimized for most elements of that range as theoretically could be done.

[eromitlab]

ah, I see much more clearly now. ;)

Thanks for the clarification Mr. Shanbaum. :)