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Thread: Short Fit defaults

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    Short Fit defaults

    I recently had a phone call with one of the lab techs at the local lab we use. He informed me that unless otherwise specified, they were defaulting their PAL corridors to short fits (12 to 14mm) since the beginning of the pandemic. This was inspired by an increase in laptop and tablet work and the lab has seen success so far.

    I haven't had any non-adapts myself so far with their lenses and I haven't had any complaints of distortion, blur, etc that I have had in the past with other short fits.

    Have any of you found that shortening the corridor, regardless/ in spite of RX been successful recently and are you selling more short corridor PALs these days?

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    Compulsive Truthteller OptiBoard Gold Supporter Uncle Fester's Avatar
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    The rabbit hole is waitng for you to jump in...again!!!

    Here is a ten year old Hall of Fame thread that I've found very helpful in explaining progressive designs. Especially Sharpsticks explanation toward the bottom.

    Ask the lab if they have a contour plot picture of the design. I find them fun to look at.

    The Hall of Fame thread also has a 20 year old 6 page discussion by other guru's that is quite meaty in the middle with the late Titan Zeiss lens designer, Darryl Meister contributing.

    https://www.optiboard.com/forums/showthread.php/53365-Progressive-Design-Classification-Has-it-gone-too-complicated?highlight=fountain+design

    Some may find this Seidel abberations explanation informative over why all progressive designs are created with compromises:

    http://www.quadibloc.com/science/opt0505.htm
    Last edited by Uncle Fester; 06-15-2022 at 09:02 AM. Reason: Tweak...

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    Compulsive Truthteller OptiBoard Gold Supporter Uncle Fester's Avatar
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    Quote Originally Posted by ODoS_HBB View Post
    I haven't had any non-adapts myself so far with their lenses and I haven't had any complaints of distortion, blur, etc that I have had in the past with other short fits.
    Just curious as to what designs are you switching them out of.

    I've always found 85%* of the success of a fit is dependent on the skill of the optician with proper frame selection.

    *Ok...that's a number plucked from a sphincter muscle that is not my iris;)

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    Compulsive Truthteller OptiBoard Gold Supporter Uncle Fester's Avatar
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    "Although mathematically the personalized lens produces better image quality, there are still 20% of users preferring a basic lens.
    There are different factors for this preference, one
    of them is that the advantages of personalization are not the
    same for all prescriptions and vary depending on the base curve selected for the calculation. When the base curve selected for a
    basic lens is close to the optimal one, the lens performance is closer to the personalized one. Another factor is the mounting
    and fitting of the lens; even if the fitting was carefully done, errors in the position of wear have a significant impact on
    final user perception. Finally, some users are less sensitive to the improvements on the personalized lenses, either because
    of a low visual acuity or because they are less sensitive to a defocus of the lens. These effects sometimes are combined and
    make the user not feel any significant differences between the personalized and basic lens, and then the selection of the design
    is done almost randomly. But when analyzing the preference of the personalized designs, the lens is preferred by most of
    the users and this is statistically significant pointing that this improvement is real and perceived by the majority of the users."

    Check out what I just found showing contour pictures:

    https://skylab-optical.net/forms/JOJ...tisfaction.pdf
    Last edited by Uncle Fester; 06-15-2022 at 09:40 AM. Reason: And as always Ryser's Rule apllies...

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    Quote Originally Posted by Uncle Fester View Post
    Just curious as to what designs are you switching them out of.

    I've always found 85%* of the success of a fit is dependent on the skill of the optician with proper frame selection.

    *Ok...that's a number plucked from a sphincter muscle that is not my iris;)
    I fail to see what the esophageal sphincter has to do with this

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    Thanks Uncle Fester, I appreciate the knowledge dump. I've read through one of the forum posts before, but I'll give it and everything another read.

    In response to your question; many patients previously wear either Varilux comfort/physio DS or Nikon Presio Power/SeeMax (The ODs in town love Nikon PALs.) I'm fitting them with Riverside Optical Lab "Persona Sigma" lens (I know it's based on IOT designs, but that's about it.) Between frame selection and setting expectations I wasn't worried about changing them, it was just a surprise to me when I found out the default for this lens was 12mm and not 16mm.

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    Quote Originally Posted by ODoS_HBB View Post
    Thanks Uncle Fester, I appreciate the knowledge dump. I've read through one of the forum posts before, but I'll give it and everything another read.

    In response to your question; many patients previously wear either Varilux comfort/physio DS or Nikon Presio Power/SeeMax (The ODs in town love Nikon PALs.) I'm fitting them with Riverside Optical Lab "Persona Sigma" lens (I know it's based on IOT designs, but that's about it.) Between frame selection and setting expectations I wasn't worried about changing them, it was just a surprise to me when I found out the default for this lens was 12mm and not 16mm.

    The current iterations of the comfort w2/physio w3 both have pretty short fitting heights of 14mm so that could by why your patients are adapting well.

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    Compulsive Truthteller OptiBoard Gold Supporter Uncle Fester's Avatar
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    Quote Originally Posted by Alex Camblor View Post
    The current iterations of the comfort w2/physio w3 both have pretty short fitting heights of 14mm so that could by why your patients are adapting well.
    The problem is also lack of a standard for "full" add power as Big E liked to say 85% of the full add power is close enough to call it 100%.

    When frames got very narrow 20 years ago this was what they conjured up to say the previous minimum fit height of a Comfort was 22 but now was 18 for the same lens.

    So does anyone know did that change?

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    IMHO it really depends on how far the patient sits from their monitor.
    22+/- inches a long corridor would be best with the longer intermediate
    16+/- they will be using the near zone therefore the short.

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