In Mary's case, the abducens is affected/ The abducens is a motor neuron that is responsible for innervating the lateral rectus muscle, this helps the pull the eye in a lateral direction. In Mary's case, only the right branch of this is affected so when she looks right the eye is simply not able to rotate laterally and she has double vision. The medial rectus muscle that is found in the right eye is responsible for pulling the eye so that she can look left. The oculomotor nerve is in charge of innervating this particular muscle and when it comes to mary's case, her cranial nerve III is not affected.
