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      Couldn't they come up a better marketing term than that?? Sounds more like ED product tech :giggle:


        Originally posted by drk View Post
        Evaluating lens performance using “volume of acuity”

        We used to call that 20/Happy. Barry Santini, you out there?


          Originally posted by wmcdonald View Post
          We used to call that 20/Happy. Barry Santini, you out there?


            Late to the game as always but as an optometrist who has happily dispensed many pairs of Varilux S (2015 - 2018) and X (2018 - present), with mostly good results, here's my observations on these two designs... just my personal opinion and understanding of the designs, not necessarily the gospel truth.

            TLDR: not the easiest designs to dispense, very reliant on 1) fitting, 2) managing wearer expectations.

            Explanations as follows, I've tried to keep it brief :)

            Disclaimer: I do not work for Essilor, I'm lucky enough to have worked for employers who don't limit what I dispense, and I believe I've had solid lens reps over the decade or so I've been dispensing.


            Varilux S

            Worthwhile to revisit the logic of the S-series, since as I understand it, the X-series mainly adds Xtend function to the basic S design.

            S design, as I know it, focuses on reducing swim effect via a design feature named Nanoptix. Works by placing all the progressive optics on the back surface of the lens, while the front is steeper convex at the distance portion, becoming slightly less convex moving downwards (think the reverse of a Camber blank as best I could figure out). The logic being that flattening the lens towards the bottom reduces magnification moving down the corridor, thereby reducing swim.

            While this 'reversed geometry' design might reduce swim as such, this may also cause a 'softening' of the near vision somewhat, especially in hyperopes who might notice the difference in clarity through a flatter near zone.

            Once I'd wrapped my (significantly alcohol-pickled and hyperactive) mind around these points gleaned from various reps, I decided to only dispense Varilux S to:
            - Patients whose concern was more to comfort of a progressive than crystal clarity
            - Following from that, hyperopes (who I reasoned, would notice more benefits from a flatter lens than myopes)
            - Since it's a dual-surface design in some way, I deduced that it would be extra sensitive to position of wear, and so used the S Fit for cases where the fitting deviated from the POW values provided by my Essilor rep

            And for the most part, it was good years with the S-series using those personal rules of thumb.


            Varilux X

            So along came this souped up design with Xtend technology.

            As I understand it, Xtend makes only a portion of the corridor behave similar to a multifocal contact lens. Can't recall the exact figures, but I was told by my then rep that the Xtend function is restricted to just between the midpoint of the corridor and just above the near circle. So, basically the lower half of what we'd consider intermediate distance.

            It was further explained to me that unlike traditional progressive optics, where as you move down the corridor, the add increases, this Xtend zone (for lack of a better term) was designed and surfaced such that the upper half of the zone could provide functional vision at intermediate range normally only viewable through the bottom half of the Xtend zone. And vice-versa for the bottom half of the zone, which could provide functional vision corresponding to an intermediate range normally only viewable through the upper half. Therefore providing a wider depth of focus for intermediate viewing tasks, only when using this Xtend zone.

            With regards to the term Volume of Acuity, this then made sense to me, since traditionally we consider progressive lens designs in terms of how wide the clear zones are (a 2-dimensional measure), but the X-series allegedly intended to enhance front/back range of clear vision (expanding range of clear vision along a third axis closer and further from the wearer, making it 3-dimensional measure of volume of space which can be perceived clearly). So far, so good for me.

            My thoughts on this, from 2018 - present:
            - If true, Xtend function only needs to cover a portion of the addition, instead of the full addition as per a multifocal CL, so the surfacing might be less complex than expected.
            - While multifocal CL often have softening of vision clarity, the Nanoptix base design already has that anyway, so perhaps it masks the potential drawbacks of Xtend.

            From there, I kept dispensing only to patients I'd normally use the S-series for, and frankly, I did not sell it for the Xtend function at all. The price difference from the S-series wasn't a huge jump then anyway.

            Anecdotal feedback from patients indicates that switching out from X-series into other designs felt like they had to exert more downgaze and/or neck movements to achieve certain intermediate tasks (viewing GPS when driving, or the upper half of a page of text being in focus with what felt like less eye movements with the X lens, and most notably reading in bed), which aligns with the claims made of the Xtend technology to me.

            Also, I have had more of the above feedback from those wearing the lenses such that the Xtend zone was more readily accesible (short corridors, or frame fittings that kept the lower half of the lens nicely within reach). Which to me verifies the rep's claim that the Xtend zone is limited to the lower portion of the lens.

            And lastly, mirroring my earlier experience with S Fit, the X Fit performs noticeably more consistent for position of wear deviating from the standard X design.


            So... that's just my experience using the Varilux X family of lenses. It's been mostly positive and profitable over the last 5 years or so, and frankly I've not had adequately bad experience with these lenses to stop using them. Maybe my reps successfully sold me snake oil, maybe my patients are easy to please, and maybe I'm just a lucky guy the optical gods chose not to give many non-adapts. But I've had a good time with the S and X series so far, and Essilor/Nikon products in general.

            Your mileage may vary, though :)


              Great feedback!


                OK, a year later I saw (a new) essilor rep. Very nice, straightforward and pretty knowledgeable.

                To re-hash:
                The WAVE technology is old stuff (wavefront-inspired I think, from LASIK) where essentially the digital surfacing and the mathematics reduce higher-order aberrations. Whatever. Can't hurt.

                The Nanoptix technology (represented by the beehive thingy) is more along the lines of flattening the inferior-temporal curvature of the PAL in order to reduce swim/extend the focal point (reminds me of the Definity design goal).

                The X stuff has the "extend technology" which is fascinating to me, and Andy thinks it's in the lower corridor to improve depth of focus and eliminate excessive head tilting as you search for the clear zone on an intermediate task.

                Also, and it's improved in the XR, is the design goal of reducing left lens/right lens disparities in power, which doesn't always apply but is nice in cases of unequal powers. (We used to have that "design by pair" technology before, but I think it applied to something limited like near zone width. I think this is a more global lens approach.)

                Bottom line for me, to dumb it WAY down, is that essilor continues to value single-vision-like design goals, so that their lens is comfortable to wear. If I'm not mistaken, the converse design goal of particularly "crisp/high contrast" vision would be lacking.
                Last edited by drk; 01-03-2024, 12:27 PM.


                  So, with a pleasant year end (belated Merry Christmas and a Happy New Year to all) behind me, and the dust settling from the usual colourful state of affairs called annual close of business... :)

                  I went digging for the old Varilux X white paper, as I thought I'd find the relevant information there. And find it I did :D

                  White paper available here:

                  And to help those who maybe are slower readers or who lack the time and/or inclination to go through the entire document, attached are clippings from the white paper showing how Essilor emphasises what they define as vision within arm's reach, the specific portion of the addition range attributed to that arm's reach vision, and also a progressive lens map showing where it is (which I believe is somewhere about the lower half of the corridor due to the addition range specified, regardless of actual corridor length).

                  TLDR: Xtend focuses on the part of the corridor corresponding to 60-85% of the wearer's prescribed addition (expected to improve depth of field and reduce necessary eye movements for working distances ranging from 16-28 inches).

                  Click image for larger version

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                  Last edited by AndyOptom; 01-04-2024, 05:22 PM.




                      Make an offer...I can be bought!!!

                      Originally posted by drk View Post
                      OK, essilor reps seen today. There has been, I've noted, a foray into "depth of focus" a lot, lately.
                      I'm going to trade mark "Conceptual Perception" Monday!


                        I'm thoroughly unimpressed with any lens not named the Autograph Intelligence. They are all either not as good or way overpriced. Just my 2 cents. They've done 3 software updates since release and haven't renamed the product once. I like that.
                        Zeiss and Varilux can go jump in a lake with their new names every 9 months. lol have a great day all!