On a Snellen chart we determine the line that the person can just recognize. If that line is twice as large as the reference standard (20/20), we state that that personâs MAgnification Requirement (MAR) is 2x. If the MAgnification Requirement is 2x, the visual acuity is 1/2 (20/40).
Posterior cranial fossa: It is the deepest and most capacious of the 3 cranial fossae. It contains the cerebellum, pons, and medulla oblongata. The foramen magnum is located centrally and inferiorly in the posterior fossa.
(ponz, pon'tÄz), 1  1. neuroanatom the pons varolii or pons cerebelli; that part of the brainstem between the medulla oblongata caudally and the mesencephalon rostrally, composed of the basilar part of pons and the tegmentum of pons.