Hi all,
This is my first post. Your discussions helped me a lot and I want to thank you all of you!
We've got in our LAB the following prescription:
Sph: 0.00 Cyl +0.50 Ax 75 Prism 6DP base up, Index 1.592
By using the thin prism approximation formula I grinded in a prism of 5.80° at 270
6/(100*0.592) and then to degrees
The resulting lens at geometrical center is only 5.50D base up
In 99% of the cases, even with torical lenses, this formula works correctly. It seems to fail only with pure and high oblique cylinders.
How can I calcualte the correct prism angle for the generator, taking into account those cases ? This formula doesn't take care about the lens power at all.
Thank very much for your help
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