The Opticians Handbook received this question about a prism Rx for a patient experiencing vertigo:
"I recently got a prescription where the doctor asked for 1.5 degrees of prism base down at axis 255 right and 1.5 degree base down in the left at axis 255. What should I order? The doctor told me to order 1.1 base down with 0.50 Base Out right and 1.1 Base Down with 0.50 Base In."
The most common way of correcting vertical imbalance is to induce a
vertical prismatic effect in the lower half of one lens. This type of
correction is referred to as bi-centric grinding, or slab-off.
