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We have a patient whos' doctor has prescribed combined prism in both eyes with a slab-off. Patient is currently wearing a progressive hi index lens.
Rx: od: +.75-.50x145 4bd 4bo
os: -4.00-1.50x180 3bu 4 bo
+2.75 add ou
Will a slab-off change prism in a progressive(in lft eye)????
No.....it will not affect the bi-centric grind in any way.
Patient has struggled with double vision for years. She went to University of Wisconsin where the Doctors were very specific in prescribing her prism. With a slab-off being base down prism, and the doctors asking for prism Up in that eye, will we be safe using the slab-off? The patient has tried a line but refuses to have a line showing, eventhough it is the best way to go .
Quote:
Originally Posted by mwh1058920
That left eye's gonna be awefull thick on the 270, you may want to find a frame that the progressive can fit as high as possible in, something with maybe a 10mm top of the frame to the fitting. The slab off is going to be base down prism the removal of base down prism I should say so it will add to the existing base up rpism, which si why I suggest a frame with a smaller frame top to DRP. To answer your question no it will not effect the prism imbalance in the top, that will remain the same, the imabalnce in the bottom will be corrected so that it is similar to the prescribed imabalance, using a slab off.
I like to draw the lens cross and place the powers accordingly and then move the cross in the direction of the prescribed prism. WOW, then you can get the visualization of how they will look. Then add the slaboff. Graphics help to see what is happening what you will need to do in frame selection.Quote:
Originally Posted by HarryChiling
Slabbing off the OS will help with the edge thickness, and in using a PAL, Prism thinning will affect it.
Harry, take my picture and work on it to make it perfect. In the picture, the oval represents an eyewire shape, while the circles around the crosses represent the actual lens. I tried to make them look thinner and thinner where applicable. It would take a long time, and/or I don't have the graphic tools.
Diane
Anyone notice how the above drawings appear to be 3-D and the black elipses seem to be circular drawing facing out. Differeing amount of face out effect in each.
Chip
What are you talking about Chip?Quote:
Originally Posted by chip anderson
Diane
but if you think you could fix them, please feel free. Graphics work...Quote:
Originally Posted by chip anderson
Diane
Don't think they are broken or bad or anything. Just observed 3-D effect in the drawings. They are great, just interesting. It was more or less a compliment.
Chip
http://www.optiboard.com/forums/showthread.php?t=3538
In this case the right eye will turn up and in, the left will turn down and in.
I would consider SV readers or a slabbed (slab-off/bicentric) segmented, especially if there are frequent close tasks. You could probably skip the slab on the PAL if you use separates. Trial frame this if you can. Hopefully the deviation is comitant (the same in all directions of gaze).
Here's a Chip approved example; I hope. :D The black crosses represent the mechanical centers and the red and blue crosses represent the optical cross aligned with the correct meridians you'll also notice that I placed th optical centers where the prism would place them aproximately anyway. This shoudl give you and indication of how the thickness will play into a prescription such as this. While it's nice to see a visual don't expect Diane to make one for you everytime, or chip to complain about it's loo, or me to make another. ;)
*I hope no opticians were harmed in the making of this post, all names are made up to protect the innocent or at least the not so guilty.
LOL:)Quote:
Originally Posted by HarryChiling
Diane
Quote:
Originally Posted by HarryChiling
I agree with Harry and William, and Harry is right the left will be very thick. :cool:
Multiple pairs of S.V. glasses. And sell her a purse to carry them in!