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Thread: Progressive Slab Off Calculation

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    Progressive Slab Off Calculation

    Need help with slab off calculation:


    R sph +4.0 cyl +1.0 A 40 Add 1,25
    L sph +1,5 Add 1,25

    A:52
    B:32
    PD:32
    DBL:18

    Pupil high: 19mm
    Reading level from PRP(Dot): 11mm


    Where should the slab off line be located on progressive Lenses?

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    Quote Originally Posted by Rafael View Post
    Need help with slab off calculation:


    R sph +4.0 cyl +1.0 A 40 Add 1,25
    L sph +1,5 Add 1,25

    A:52
    B:32
    PD:32
    DBL:18

    Pupil high: 19mm
    Reading level from PRP(Dot): 11mm


    Where should the slab off line be located on progressive Lenses?
    The biggest problem with progressive slabs is where you gonna match the prism. You can only calc the slab to match at one point. I would suggest not slabing it to begin with. If you have a problem then, you can always refit and add the slab. It will be very expensive and probably useless to the patient to slab a progressive. There are millions of people out there reading with one that do not even realize it and are doing fine.

  3. #3
    ATO Member OptiBoard Bronze Supporter HarryChiling's Avatar
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    At the PRP. Let the lab do it if you want it no need in stressing your brain that's what we get paid for, oh sorry I thought you were a dispenser from the US. Calc it at the NRP and slab it at the PRP.

    Right = +4.50 @ 090
    Left = +1.50 @ 090

    11mm from PRP

    Right = 5.00D BU
    Left = 1.65D BU

    So slab the left 3.25D

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    Quote Originally Posted by Rafael View Post
    Need help with slab off calculation:


    R sph +4.0 cyl +1.0 A 40 Add 1,25
    L sph +1,5 Add 1,25

    A:52
    B:32
    PD:32
    DBL:18

    Pupil high: 19mm
    Reading level from PRP(Dot): 11mm


    Where should the slab off line be located on progressive Lenses?
    Contact 'SLABS Plus' the Slab-off specialists located in Florida. They will know exactly where to place the slab-off line.

  5. #5
    The Man, The Myth, The Legend OptiBoard Gold Supporter Fezz's Avatar
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    Quote Originally Posted by HarryChiling View Post
    At the PRP. Let the lab do it if you want it no need in stressing your brain that's what we get paid for, oh sorry I thought you were a dispenser from the US. Calc it at the NRP and slab it at the PRP.
    I have been taught that the slab should be further down in the channel. The reasoning is that there is such little add power at the PRP, that the patient may still experience some imbalance in the lens as the eye travel down the corridor.

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    ATO Member OptiBoard Bronze Supporter HarryChiling's Avatar
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    Quote Originally Posted by Fezz View Post
    I have been taught that the slab should be further down in the channel. The reasoning is that there is such little add power at the PRP, that the patient may still experience some imbalance in the lens as the eye travel down the corridor.
    Yeah I guess technically your right if your to match a FT or an Exec the grinding would only be in the Near Vision so lower in the corridor would be similar, but I have always placed them closer to the PRP in progressives and never had a complaint. I usually use a progressive with a 4mm DRP to PRP so it gives enough room to not bother on distance gaze, but I guess lower would be better especially if the drop if less like for instance the 2mm drops or the seiko's which are on the 180.

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