Fig 11. For patients requiring a different prismatic prescription in primary and down gaze, there are two different solutions with Fresnel membrane prisms. The first consists of grinding prism in the carrier lens, and adding the additional prismatic power regionally with a Fresnel prism. The lens on the left is an example of this method. The lens on the right consists of a carrier lens of no prismatic power that has two Fresnel prisms of different powers applied to it.