Conjugate gaze is mediated in the brain stem by the medial longitudinal fasciculus, which is a nerve tract that connects the abducens, trochlear, and oculomotor nuclei. These nuclei, in turn, are responsible for the muscles that control eye movements. The left pontine center connects with the right frontal center for conjugate gaze to the left, and the right pontine center connects with the left frontal center for conjugate gaze to the right. If extraocular muscles are not working properly, dysconjugate gaze can result, which can then cause diplopia. The mechanisms for horizontal eye movements are better...