Final answer:
In bilateral medial longitudinal fasciculus (MLF) syndrome, when the patient tries to look left, their right eye does not move inward, leading to misalignment of the eyes and diplopia, or double vision.
Step-by-step explanation:
When a patient has bilateral (BL) medial longitudinal fasciculus (MLF) syndrome, and they are asked to look to the left, their eyes might not exhibit normal movement. One eye (the left eye in this case) will abduct normally, moving outward to the left.
However, the other eye (the right eye in this case) will fail to adduct, or move inward, to follow the leftward gaze. This is due to internuclear ophthalmoplegia (INO), which occurs when there is damage to the MLF pathway that coordinates eye movements. As a result, the affected individual may experience diplopia, or double vision, because the eyes are not properly aligned.