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Thread: Freeform SV - quantifying the improvement

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    Freeform SV - quantifying the improvement

    A patient is considering freeform for SV (high minus, probably 1.74) and asked a great question: how much improvement can I expect? Obviously for progressives the improvement is dramatic, but has anyone seen a page or video that shows or quantifies the improvement over stock lenses in different SV situations?

    The manufacturers' freeform SV marketing pages do the opposite - few details and no example images or side-by-side comparisons against the best stock lenses. https://www.optiboard.com/forums/sho...-vision-lenses is the closest thread I found, and it doesn't have anything objective or even a subjective consensus, and it's 8 years old.

    I'd be a bit more inclined to consider freeform SV for a high plus prescription. Cost isn't a concern here, though - the patient is willing to pay for the best. They asked the right question: what improvement, if any, can I expect? I'd like to be able to get more specific than "Not a ton, but probably some."
    Last edited by roy781; 12-15-2021 at 10:19 AM.

  2. #2
    What's up? drk's Avatar
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    I think it's pretty impossible to do that on a case-by-case basis.

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    Is the patients name Roy and are they from Oregon?

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    Compulsive Truthteller OptiBoard Gold Supporter Uncle Fester's Avatar
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    "They asked the right question: what improvement, if any, can I expect? I'd like to be able to get more specific than "Not a ton, but probably some."

    My reply to this is: "That it is a subjective question and I have found some patients who will report a dramatic improvement while the same rx with another patient finds no difference. How you will respond is impossible for me to know until you try the lens. There is usually an improvement."

    I always suggest they try the best if cost is not a concern but can never guarantee (refund) customized lenses that have already been made. The more complex the rx the more I will push them to try it- especially if the cost difference is affordable to them.

    Watched a great PBS show last night on DaVinci and one segment had an expert commenting on retinal rods and cones and how our eyes usually move 3 times per second to give us our best image of an object. Correct me if I am wrong when I say to patients that they "see" about a centimeter or little fingers fingerprint size area of a lens before you move your head to see an object in its entirety.

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    What's up? drk's Avatar
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    Here's how I see it: "it's complicated".

    And let me get this out of the way: complicated doesn't belong in the hands of the patient. You don't ask them if they want FFSV. You give it to them if they need it. Save the "options" for add-ons like photochromics or anti-reflection.

    How do we know if "they need it"? Here's the complicated answer.
    1. As a giant group of people (not an individual) FFSV is needed, because the group will get better vision on the whole. Some more, some less, some none.

    2. Any given individual is difficult to judge. Are they sensitive? Did they just go up in eyesize? Are they anisometropic? Is there a change in correction that may be difficult to tolerate? Is their axis oblique, WTR, or ATR? Does their lens power fall at the extremes of the base curve choices? Are they just happy to see better because their old glasses were crap?


    So, what are some options as an optical?
    1. Do nothing. Keep everything as cheap as possible. That's why they come to you. (Most will do this, but not Optiboarders.)
    2. Put everyone in FFSV, and while you're at it, probably package a good AR, and a good material. They'll be SURE to see their best. That's why they come to you.
    3. Try to pick and choose who you think would benefit...the obvious ones. The anisometropes, the high cylinders, the high powers. They'll see their best and those that don't need it won't pay extra.


    So, how would this possibly look?

    ("Basic lens" which is CR39, but you never do that unless you have to.)

    "Polycarbonate lens": "Thinner, lighter, stronger, UV protection, scratch-resistant." (You can always sell up from here...bells and whistles and AR and photochromic.)

    "Custom lens": "Custom computer-designed and fabricated to make your vision the clearest and most comfortable, thinner, lighter, and reflection-free. You need this for your (insert special situation here) vision problem."

    Put people in one or the other box. Don't offer. This is not an option, this is a prescription and a lens design process. Just sort them into the correct box and if they don't like it, then they can get the lower tier. When anyone writes a prescription for medical treatment or spectacle lenses or contact lenses or plans a surgical procedure, the patient isn't going to need to know each and every choice that's out there. They're in your office for YOU to make a great decision on their behalf. If there is an obstacle to your treatment plan, then you address it and modify it. But only if there's an obstacle.
    Last edited by drk; 12-16-2021 at 10:36 AM.

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    Quote Originally Posted by drk View Post
    Here's how I see it: "it's complicated".

    And let me get this out of the way: complicated doesn't belong in the hands of the patient. You don't ask them if they want FFSV. You give it to them if they need it. Save the "options" for add-ons like photochromics or anti-reflection.
    No way Roy isn't a consumer.

    Wouldn't it be nice if there were trained knowledgeable professionals that could do this sort of thing? (though I don't consider AR coating an option). I'm not really on board with your basic, poly, custom tiers either, but that's minutia.

  7. #7
    What's up? drk's Avatar
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    Let's have a robust debate!

    Kwill: "AR is a must".
    Drk: "I don't disagree. I need to promote it more."
    Kwill: "You know what they say, drk: 'the first person you need to sell is yourself'".
    Drk: "Quite right".


    Kwill: "I hate polycarb and you're an axe murderer."
    Drk: "No, polycarbonate is great."
    Kwill: "I like 1.6 because I'm fancy. I'll use Trivex before I'll use poly. Blech."
    Drk: "OK, 'super-optician'."

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    The second half gave me a good chuckle doc, thanks. I try not to bash people's choice to use poly too much, but I just don't understand it's purpose.

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    Eyes eastward... Uilleann's Avatar
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    There is literally NOTHING wrong with poly, in the power range that savvy opticians would wisely choose to use it in. You're more likely to get any random sample of pt's to notice the difference between a "digital" or "freeform" lens vs a grinder, long before any would notice the optical/visual difference between Trivex/poly/1.60.

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    OptiWizard KrystleClear's Avatar
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    I never know how to answer questions like that, because everyone is different and some people are more sensitive to changes than others. Some people seemingly notice a single degree change of axis while others seem to see no different in their vision when the doctor swaps a -0.50 to a -1.00 in the phoropter. People with -0.25 OU will say they're so blind, while you have the occasional -4.00 OUs out there driving uncorrected with no clue they needed glasses. The best you can do is educate them on the concept and how they are made, and hopefully that builds the value for a freeform upgrade for the patient.
    Krystle

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    Master OptiBoarder OptiBoard Silver Supporter Barry Santini's Avatar
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    The biggest problem with poly is the tendency for this material to be mated with unusually flat curves.
    Steepen those curves and performance improves.

    Barry

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    Master OptiBoarder OptiBoard Silver Supporter Barry Santini's Avatar
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    Done right, FFSV allows a more comprehensive tailoring of the optics, PRP/OC and base curve choice fir a soecifuc Rx and frame.

    Accept few substitutes.

    B

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    What's up? drk's Avatar
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    Barry, can you expand on the base curve problem? Thanks.

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    Compulsive Truthteller OptiBoard Gold Supporter Uncle Fester's Avatar
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    Quote Originally Posted by Kwill212 View Post
    ... I try not to bash people's choice to use poly too much, but I just don't understand it's purpose.
    To give opticians like my wife sarcoidosis?

    Always wear a mask when edging poly.



    https://www.webmd.com/lung/arthritis-sarcoidosis

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    Master OptiBoarder DanLiv's Avatar
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    Quote Originally Posted by Barry Santini View Post
    The biggest problem with poly is the tendency for this material to be mated with unusually flat curves.
    Steepen those curves and performance improves.
    Quote Originally Posted by drk View Post
    Barry, can you expand on the base curve problem? Thanks.
    I agree with Barry, the industry has defaulted to poly as a cosmetic option first and foremost, vision second. Especially with aspherics. They do tend to default to a diopter or two flatter base curve than best form. Sure aspheric and freeform atoric can compensate for some of this, but that wastes some of the performance benefits of aspheric and atoric just to make up for cosmetic compromise.

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    Quote Originally Posted by Uilleann View Post
    There is literally NOTHING wrong with poly, in the power range that savvy opticians would wisely choose to use it in. You're more likely to get any random sample of pt's to notice the difference between a "digital" or "freeform" lens vs a grinder, long before any would notice the optical/visual difference between Trivex/poly/1.60.
    Quote Originally Posted by Barry Santini View Post
    The biggest problem with poly is the tendency for this material to be mated with unusually flat curves.
    Steepen those curves and performance improves.

    Barry
    Quote Originally Posted by DanLiv View Post
    I agree with Barry, the industry has defaulted to poly as a cosmetic option first and foremost, vision second. Especially with aspherics. They do tend to default to a diopter or two flatter base curve than best form. Sure aspheric and freeform atoric can compensate for some of this, but that wastes some of the performance benefits of aspheric and atoric just to make up for cosmetic compromise.
    So to summarize, basically the problem with poly isn't poly itself but just that the optical industry tends to use flatter base curves for aesthetic reasons instead of using optimal curves that fit the frame and rx the best?

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    Quote Originally Posted by DanLiv View Post
    I agree with Barry, the industry has defaulted to poly as a cosmetic option first and foremost, vision second. Especially with aspherics. They do tend to default to a diopter or two flatter base curve than best form. Sure aspheric and freeform atoric can compensate for some of this, but that wastes some of the performance benefits of aspheric and atoric just to make up for cosmetic compromise.

    I don't understand. The entire purpose of aspheric lenses(outside of necessity for high plus) is to make flatter lenses with comparable performance to best form lenses. Of course they default to flatter curves than best form. Who makes best form lenses anyway? Anyone? Are there any +2.00 lenses coming on 8 base by default? -4.00s on 4 base? I haven't seen it. Where is the cutoff for base curve deviation that can be addressed with aspheric lenses? I honestly have no idea.

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    The breaking point is +2.25 that should be on an 8.00 bc on any standard finished lens. The adherence to a standard BC chart went out the window when frames became standard that had BC restrictions on them. Same have to be be on an 8.00 all the time others can’t hold an 8 00. So lens design had to be corrupted to satisfy the frames. Making an aspheric design will over come some of those crazy frame requirements. There was a lens company now extinct called Univis they invented the glass ft bifocal and produced finished sv lenses in glass that were called Best Form. It was a competitor to American Optical first minus cyl finished glass lenses called masterpiece. That was the beginning of the end of front side cyl lenses. Lenses had to get bigger to accommodate the new large size frames that became popular in the 60’s. It was easy to make 71 mm lenses with cyl on concave side almost impossible to that on the convex side. The transition time was difficult as some patient multiple pairs constructed in both designs and found it difficult to switch back and forth.

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    Master OptiBoarder OptiBoard Silver Supporter Barry Santini's Avatar
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    Quote Originally Posted by drk View Post
    Barry, can you expand on the base curve problem? Thanks.
    The amount of Refraction at an interface depends on two things:

    1. The obliquity of incidence
    2. The difference in the indexes on each side of the interface

    Therefore flat ploy is the worst.

    Barry

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    Master OptiBoarder DanLiv's Avatar
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    Quote Originally Posted by Kwill212 View Post
    The entire purpose of aspheric lenses(outside of necessity for high plus) is to make flatter lenses with comparable performance to best form lenses. Of course they default to flatter curves than best form. Who makes best form lenses anyway? Anyone?
    Quote Originally Posted by NAICITPO View Post
    So to summarize, basically the problem with poly isn't poly itself but just that the optical industry tends to use flatter base curves for aesthetic reasons instead of using optimal curves that fit the frame and rx the best?
    The true purpose of aspheric lenses is to compensate for spherical aberration present even in best form lenses. But as Lensman11 says best form has been corrupted in service of cosmetics, and aspheric technology abused merely to offset the intentional degradation of the desirable "thinner and flatter" lens.

    Poly's performance is slightly lower to begin with, but screw up it's best form, make it aspheric, and put it in the hands of poor opticians that don't understand fitting buttons or bother with SV OC heights, and viola you have a crappy lens.

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    Eyes eastward... Uilleann's Avatar
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    Quote Originally Posted by DanLiv View Post
    ...Poly's performance is slightly lower to begin with, but screw up it's best form, make it aspheric, and put it in the hands of poor opticians that don't understand fitting buttons or bother with SV OC heights, and viola you have a crappy lens.
    In fairness, the exact same can just as easily be said for CR/glass.

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    One eye sees, the other feels OptiBoard Silver Supporter
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    Quote Originally Posted by Kwill212 View Post
    I don't understand. The entire purpose of aspheric lenses(outside of necessity for high plus) is to make flatter lenses with comparable performance to best form lenses. Of course they default to flatter curves than best form. Who makes best form lenses anyway? Anyone? Are there any +2.00 lenses coming on 8 base by default? -4.00s on 4 base? I haven't seen it. Where is the cutoff for base curve deviation that can be addressed with aspheric lenses? I honestly have no idea.
    Yup, choose carefully (see below). I would designate any lens that has a design goal of minimizing peripheral aberrations as best form.

    I'm a big fan of higher Abbe, flatter, POW optimized Atoric/aspheric lenses, especially from manufacturers that have very capable software with no compromise optics (Zeiss for example), resulting in improved appearance, reduced magnification/minification, and optimal primary and peripheral optics, usually a welcome improvement for the spectacle lens wearer.

    Robert
    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.



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    Quote Originally Posted by DanLiv View Post
    Poly's performance is slightly lower to begin with, but screw up it's best form, make it aspheric, and put it in the hands of poor opticians that don't understand fitting buttons or bother with SV OC heights, and viola you have a crappy lens.
    Well yeah, if the person making the glasses doesn't understand basic optics they can make a bad pair of glasses regardless of the abbe value of the lens, right? How are you differentiating the dumb sales people (not opticians) who don't understand basic principles and the lens manufacturers who are looking to make thinner lenses at the expense of optics from the abbe value of the lenses? It seems you are lumping them together.

    If you were to use the correct base curve and the frame was measured and fit by an experienced optician what's the difference the wearer is going to experience due to a 32 abbe for poly and a 45 for trivex? In my experience it hasn't been much.

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    Compulsive Truthteller OptiBoard Gold Supporter Uncle Fester's Avatar
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    This is really a corruption of Ryser's Rule.

    "The success of any Freeforms optical performance of a lens is directly proportional to the desire of the patient to see their best and knowledge of the optician."

    fwiw- This has been an informative thread for me as I knew most of it but not as well described as here.

    HoF thread?

  25. #25
    What's up? drk's Avatar
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    I thought Ryser's Rule was: "I don't always wear progressives, but when I do I'm tipsy anyway, because it's cocktail hour..."

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