A problem for the experts

[Bezza]

Ok heres the problem, I have a patient who has been wearing varis for quite some time now and our good friends at Zeiss have been superb in the past at dealing with her very tricky Rx but this time round they are giving me the old 'computer says no' syndrome despite having made the lenses with a very similar Rx in the past.

Anyways this is what the patient is currently wearing;
Zeiss Gradal Top 1.67 AR coat
-9.25/-3.00x20 6prism B DN
-12.50/-2.75x132 6prism B UP ADD +2.25 R+L

And heres the new Rx;
-9.75/-3.00x20 8prism B DN
-12.50/-3.00x132 8prism B UP ADD +3.00 R+L

Now i appreciate that theres an extra 4 dioptres vertical imbalance and that the ADD is higher but otherwise theres very little difference and if they managed to make up the previous pair why are they now telling me they can only do 3 B DN in the right and no prism in the left. They have put the order through to Germany a few times now and keep getting the same response.
I wonder if any of you experts out there can shed some light on this because I havent had a proper optical explaination of why they cant do it, I dont mind if i have to change the material, even hi index glass would be fine despite the weight but it would be a real shame to have to tell our patient that she can no longer have varis.

[RT]

There's probably not a thick enough blank to handle the high minus power combined with increased prism. The blank thickness more than likely varies with the add power, so just because they could do it on a 2.25 add doesn't mean they can do it on a 3.00 add.

Just a guess.

[Ory]

They've done impressive things with the Individual. have you asked about/considered changing lens styles?

[JRS]

The Rx also went from 6 Diopters prescribed prism to 8 diopters. Need more thickness within the blank.

[Bezza]

Yeah it seems that blank thickness was the issue, am surprised it took Zeiss so long to give me a proper explanation and come up with an alternative, normally they are pretty good. Thankfully they are able to make the Rx in 1.8 glass so at least I can give my patient some options now, unfortunately the lenses are gonna weigh a ton if she decides to stick with varis.