# Thread: Progressive Slab Off Calculation

1. ## Progressive Slab Off Calculation

Need help with slab off calculation:

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

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

Pupil high: 19mm

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

2. Originally Posted by Rafael
Need help with slab off calculation:

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

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

Pupil high: 19mm

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. 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

4. Originally Posted by Rafael
Need help with slab off calculation:

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

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

Pupil high: 19mm

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. Originally Posted by HarryChiling
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.

6. Originally Posted by Fezz
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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