Now that's funny!Originally Posted by Robert Martellaro
I hope they don't have to use up all of their design tools compensating for the more complex aspheric surface though.
I'll be putting the Camber through my own blind vetting process with my persnickety engineer patient base with next year's "Exploratory Budget".
depends on what you define as a "design tool"
if we are talking about zernike coefficients to optimize a conic, after about the 10th term, things get a little messy, especially from a manufacturing/metrology stand point.
"Using up the design tools", aspherics and deformed conicoids have their limits; if you are using these back side methods to cleanup the front surface created issues then the back surface becomes far to complex to compensate for additional errors. By moving the progression to the front and making it continuous across the front surface, the design can focus on the actual patient parameters on the back. Also the marginal astigmatism created by a PAL design isn't all about the diopter value, sometimes it is more dis-jarring to look through a lens that has less marginal astigmatism but is oriented obliquely than a design that has more marginal astigmatism but is oriented vertically, horizontally, or aligned with the patient prescription. This true distortion can cause floors to seem warped or shapes to look funny.
The Camber and the old Omnifocal have a lot of similarities, the Omnifocal went away because of the cost/complexity in production, that no longer exists so the Camber lens is a vintage design that may have been greater than the Varilux design which replaced it in the 60's, every design after looked more like the Varilux design, now we are actually seeing an older yet possibly better lens design reemerging. Time will tell if the design is better, just the fact that many are talking about it means that the lens is obviously a contender in the marketplace.
http://www.opticians.cc
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I'd like to see the powers of the 6% who did not feel the lens was better or as good.DISCUSSION: WEARER TEST
IOT, in association with the University of Madrid, designed and conducted a double-blind wearer trial comparing a Camber finished lens with one processed from a single vision blank. Both used the same contemporary IOT back-surface progressive design technology. Both prescriptions were made from the same material, same central base curve, in the same frame, and worn for one week each. The only difference between the two pairs of eyewear was the lens blanks they were processed from: Camber versus single vision. Wearers and testers were unaware of which lens was which. After trying them both, wearers were then asked to compare lenses.
When asked, "Which lens do you prefer the most?" wearers preferred Camber 2 to 1. Regarding ease of adaptation, 8 of 10 reported that adaptation to Camber seemed easier. Nine of 10 reported better near vision. Considering all factors, 55 percent (a majority) found Camber better, 39 percent found it to be equal.
Wearer trials like this are not very common today because it is very tough to show significant differences in wearing experiences. Test subjects find it difficult to differentiate and express their preferences. Additionally, the trials are very expensive and time-consuming to perform. Therefore, these reported results are significant.
Did they randomly vary or were they specific to higher plus/minus or cylinder powers?
People are strange.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
I always saw their claims about that as disinformation to try and combat Zeiss' horizontal symmetry patent from the 80s.
Far to complex? I'm wondering if you can restate this in a way I can understand. The design isn't being customized with a tool...these are 3d math operations and tooling instructions that of course have their limits, but those limits exist regardless of base curve.
Has the progression been moved to the front with camber? I argue yes. Others seem to be trying to argue no, while saying yes in their explanations.
My interpretation of the wearer test was that they were comparing IOT vs IOT. The limitations are in their math, and I would be curious to see how those same 6% feel about Hoya vs Seiko vs Shamir vs Zeiss designs.
Additionally, I wonder how long the patients wore each product.
Horizontal symmetry is related to how the unwanted astigmatism is distributed from the nasal to the temporal portions of the lens, with a symmetric distribution providing the best binocular balance.
Essilor's contribution was to show that the orientation of the initial bands of astigmatism on either side of the umbillic played a factor in wearer comfort, with a vertical orientation being the most comfortable.
http://www.icarelabs.com/wp-content/...LVAR200836.pdf
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
If you were to take a cone and cut it in half with the cut being parallel to the base you would have a circle, cut it at an angle to the base you have an ellipse. These, along with the parabola and hyperbola, are conic sections. They are plane curves. If you were to rotate these curves around the axes of symmetry you create the conicoids.
When you use an aspheric lens you are using a form of conicoid knows as an ellipsoid(flatter than a circle) and there are different types of ellipsoids.
We use these types of curves to reduce aberrations associated with off-axis viewing(i.e. looking into the add of a progressive).
There is a limit to what these surfaces can do.
A progressive decreases the radii of curvature as the rotates downward, so in that sense it is a progressive. The progressive optics, Pow, etc still have to be ground on the back surface. I would say it is not a front surface progressive in the traditional sense.
If we assume that the front and rear surfaces can be made perfectly(which they can't), then splitting the "3d math operations" between the front and rear surfaces, reduces the amount of corrections you need.
Normally in the form of Zernike polynomials, or some other type of higher order polynomial and/or exponential.
This is the primary argument that was/is used against digitally generated back side PAL's versus traditionally ground PAL's.
Because they both have a surface that is spherical, they will still display aberrations caused by the spherical surface.
If you can mold a front PAL surface and conventionally grind the rear spherical surface to the same accuracy and design as a digitally generated back side PAL,
then from a design/metrology standpoint, they are equal in terms of performance/amount of aberration.
The camber has a base curve variation on the front(horizontally spherical across the entire front surface), not a focusing power variation like molded PAL's(not spherical across any axis below the PRP).
If you had a SF molded PAL, such as a GT2 or a physio. You could use it as is, and it would perform like a plano distance, with an add equal to the molded add, and still have a usable corridor.
A SF Camber blank will not focus light, the whole lens will be blurry, and it does not have a corridor.
In short, the variation of front curve full add traditional progressive lens goes like this:
Distance > Convex
L Soft Focus Area, or Junk:
>Steeper Convex
>Very Steep Concave
>Moderate Convex
Reading > Steep Convex
R Soft Focus Area
>Moderate Convex
>Very Steep Concave
>Steeper Convex
Back to Distance > Convex
Note: Mix of vary steep concave and convex curves.
Compare that to the Camber:
Distance > Convex
Soft focus or Junk > Steeper Convex
Reading > Steep Convex
Soft focus or Junk > Steeper Convex
Back to Distance > Convex
note: All Convex
A traditional design goes back and forth, effectively sending any focal point over a very wide area in multiple directions, which by definition is distortion.
The Camber by contrast will keep that focal point in a smaller range, because the front lacks the horrible mix of Concave and Convex Curves present on traditional lenses. These curves exist in theory on the Camber, but well off the surface of the lens and way from a patient field of view. Its simply a magnification of the tiny entry zone of a front add progressive, say a 5 mm circle, and using and expanding that for the entire front of the lens.
I had the exact same idea about 12 years ago, and should have patented it then.
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