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Thread: Widest intermediate with a Zeiss lens

  1. #1
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    Widest intermediate with a Zeiss lens

    Just trying to determine which Zeiss Progressive gives the widest intermediate for desk top computer use.

    Yes I know nothing beats an office lens, but out of these 3, which would win?

    1. Individual 2, Active/Intermediate Design
    2. Drivesafe
    3. Energize Me

    I've found the one weakness of Zeiss lenses is their intermediate width compared to Hoya lenses.

    I was surprised to read the whitepaper on Drivesafe last night. I had assumed it was simply a very distance orientated lens, but I learned that they have actually increased the width and vertical depth of the intermediate zone at the expense of the near zone and that the intermediate kicks in a little higher up in the corridor than their other lenses. Was thinking should I be using these instead for the heavy desk top users who decline a separate computer pair of specs.

    I recently put an experienced Hoya ID Lifestyle 2 Harmony wearer into Individual 2 Balanced and she just could no longer use them at the computer. Her add only increased 0.25. So I remade them as Energize Me and she just breathed a sigh of relief when she put them on.

    Opinions?

    Thanks

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    Master OptiBoarder lensgrinder's Avatar
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    A wider intermediate comes at the expense of either reduced distance(clarity from side to side) and slower rate of change(the amount the power changes through the corridor over a given distance).
    ZEISS aims to have full edge to edge clarity in the general purpose progressive lenses, this means that these designs are hard keeping all of the surface astigmatism at or below the mid point of the lens.
    The Individual 2 and DriveSafe are both variable corridor, which means the corridor length is dictated by the center of rotation added to the vertex distance, the fitting height, PD, frame parameters and frame shape. The purpose is to produce the widest intermediate based on the above parameters, along with Add power, while reducing aberrations from side to side. The Individual 2I will increase the corridor length when compared to the balanced design and the Individual 2N will decrease the corridor length when compared to the balanced design. An increase in corridor length reduces rate of change while increasing corridor width, a decrease in corridor length has the opposite effect.
    The DriveSafe starts progressing lower than the Individual 2 and the corridor is slightly longer which means you have a wider distance and the longer corridor gives wider intermediates.
    The EnergizeMe is a soft design, like the Office Lens. Softer designs spread the surface astigmatism vertically which allows you to shorten the corridor allowing for faster rates of change while keeping the intermediate wider, but reducing distance fields of view. Since hyperopes have a shorter radius, they require a greater accommodative demand, and they lose accommodation sooner than myopes plus they are more fixed in their motions so they tend to like a softer design progressive.
    Myopes tend to prefer harder designs and usually do not mind the variable corridor, but sometimes they might need a slightly shorter corridor, this is where you can use the fixed option in a hard design.

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    Thanks lensgrinder, that all makes sense.

    With what you've said, I'm not very clear on the corridor lengths with the Individual series. If you pick a Frame Fit Value of say 4 which means a 14 mm corridor, won't you then have a 14mm corridor in all 3 designs (Balance, Intermediate/Active and Near). Is it the rate of change of the progression that's different in the 3 designs if they have the same selected Frame Fit Value?

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    Master OptiBoarder lensgrinder's Avatar
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    Quote Originally Posted by obiwan View Post
    Thanks lensgrinder, that all makes sense.

    With what you've said, I'm not very clear on the corridor lengths with the Individual series. If you pick a Frame Fit Value of say 4 which means a 14 mm corridor, won't you then have a 14mm corridor in all 3 designs (Balance, Intermediate/Active and Near). Is it the rate of change of the progression that's different in the 3 designs if they have the same selected Frame Fit Value?
    Even though the frame fit value is 4 mm the corridor will be slightly longer in the Indivdual 2I and slightly shorter in the Individual 2N. When you have a longer corridor the rate of change is less when compared to a shorter corridor which is more. For example a 9 mm corridor in a +2.00 add will change at a rate of 2/9 = 0.22 D per mm where a 14 mm corridor in the same add will change at 2/14 = 0.14 D per mm.
    Using a shorter corridor means the rate is more rapid which increases surface astigmatism which decreases intermediate width.
    I would also like to point out that the Individual has a slight increase in power, for viewing digital devices, which is a little higher than where the NRP is located. This is due to the fact that we read our devices a little closer and we do not move down the full corridor when reading them.

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