Final answer:
An MLF lesion in Internuclear Ophthalmoplegia results in impaired conjugate lateral gaze due to the inability of the lateral rectus muscle in one eye to contract, leading to diplopia. It does not involve vertical gaze, the optic nerve, or the occipital lobe.
Step-by-step explanation:
An MLF lesion in Internuclear Ophthalmoplegia (INO) leads to a deficit of conjugate lateral gaze because the lateral rectus muscle of one eye does not contract, which is typically due to damage to the medial longitudinal fasciculus (MLF) rather than the abducens nerve directly. It does not cause lateral rectus weakness per se, but rather impairs coordination between the two eyes, as the affected eye is unable to move outward (abduct). This results in the eye on the side of the lesion being unable to abduct while the other eye adducts, leading to diplopia or double vision.
INO does not result in impaired vertical gaze, involve the optic nerve, or affect the occipital lobe. The MLF primarily coordinates eye movements by connecting different nuclei that control eyemovement, particularly horizontal movements. Hence, the correct answer is that an MLF lesion in INO impairs conjugate lateral gaze.