Darryl, when I set about re-learning optics to understand Free Form, your publications on OptiCampus and in published articles, and your content embedded in presentations at Vision Expo...well,no one helped me as much as you did. Vendor reps have been great, but you make the optics almost understandable. I still have questions.
Before computers, great thinkers were using ray tracings and working from different philosophies. I'm thinking that we now have the technology to help us analyze data and measure aberrations. Best optics are best optics, an end point, and the base curves can be manipulated enough - while still providing best possible optics - so that brands can claim proprietary superiority. I trust you will tell me if I'm oversimplifying, and I know you can explain it with optics and math. I love that about you!
Recall that years ago each lens manufacturer actually offered their own proprietary "corrected curve" or "best form" lens design. Some designs primarily corrected oblique astigmatism (e.g., Zeiss Punktal), some designs corrected tangential power error (e.g., AO Tillyer Masterpiece), and so on. Each design philosophy resulted in a slightly different base curve choice for each prescription. The number of available base curves was also an important parameter associated with each lens design.
Here is the question: assuming the ability to customize with vertex, panto, and tilt, wouldn't most lens designers use weighting and merit functions to achieve pretty much the same objectives, for a Free Form Single Vision Lens? More degrees of freedom means they have more ways to manipulate the front and back topographies to achieve the same results - agreed upon best possible optics for a given Rx. Do new age thinkers with new age computer technologies hold differing philosophies regarding best possible optics for a given single vision Rx?
The introduction of free-form surfaces makes possible even more degrees of freedom, since the lens design is no longer limited to a rotationally-symmetrical surface created by simply rotating a one-dimensional surface height function around the design center. Correcting optical aberrations due to the position of wear, prescribed prism, and other factors is now possible with sufficiently advanced optical design software, which allows lens designers to control the optics at points over the entire lens surface.
So, with free-form single vision lenses, lens manufacturers now actually have more ways of differentiating their lens designs, not fewer ways.
First, lens manufacturers can define their basic lens design to achieve a variety of goals, including the correction of specific optical aberrations, manipulation of lens form or thickness, control of mangification, and so on.
Further, not all free-form lenses are created equally. The level of manufacturing quality and design sophistication may vary considerably from supplier to supplier. Unfortunately, these optical technicalities have been overlooked by many eyecare professionals today.
Darryl, I hear what you are saying, however I've been trying to understand it and manufacturers are not forthright sharing contour maps. Some are helpful; for example Hoya's My Style images are very helpful - though I know the true contours will vary with each unique Rx. Some manufacturers are just outright deceptive.
Now - please tollerate my soapbox issue:
Also, I think manufacturers benefit from sharing incomplete information. I am of the opinion that Free Form optics have wider sweet spots than conventional progressives, and that one of the biggest reasons patient's don't get a Wow is because opticians order a fitting height, call it a seg height, and let the lab select a power profile that fits the frame. Patients who enjoy short corridor lenses, and end up in long corridor free form lenses - will not be happy campers, regardless of the quality of free form optics.
Instead of teaching opticians to tailor the fixed segment height, or allowing opticians the freedom to manipulate the progressive blend zone, manufacturers are instead telling opticians they need better measuring tools. Manufacturers are selling high quality auto-refractors that have the side benefit of providing the manufacturer the opportunity to compare heaps of subjective refractions against autorefractor generated prescriptions, to continually improve the technologies that will eventually allow patients to by-pass the doctor and obtain online refractions.
I like that we can obtain better subjective refractions. I believe, in the long run, this is best for the patient. And I don't mind evolution in the optical marketplace and all the upcoming innovations that will make the internet more and more beneficial. The global impact of great refractions in undeveloped countries has the potential to improve the world.
Having said that, I really don't like manufacturers blaming doctors and opticians for not understanding the proprietary aspects of their lens designs. Darryl, you have gone a long way to help us understand that the "good" "better" "best" model is not appropriately applied to Free Form. I wish I could say the same industry wide.