 Internuclear ophthalmoplegia occurs when MS affects a part of the brain stem called the medial longitudinal fasciculus, which is responsible for communication between the two eyes by connecting the abducens nucleus of one side to the oculomotor nucleus of the opposite side.This results in the failure of the medial rectus muscle to contract appropriately, so that the eyes do not move equally (called disconjugate gaze).Different drugs as well as optic compensatory systems and prisms can be used to improve these symptoms.