Which cranial nerve can result in diplopia when damaged?

The oculomotor nerve (CN III) is responsible for the movement of most extraocular muscles, which control eye movement, as well as the elevation of the upper eyelid and pupil constriction. Damage to this nerve can lead to issues with eye movements, including difficulty in adduction, elevation, and depression of the eye. When the oculomotor nerve is impaired, there may be misalignment of the eyes, resulting in diplopia, or double vision. The inability of the eyes to properly coordinate can lead to a situation where the visual axes do not align correctly, causing one eye to deviate and the individual to perceive two images.

The optic nerve (CN II) primarily transmits visual information from the retina to the brain; its damage would not cause eye movement issues or diplopia but could affect vision clarity or field. The trochlear nerve (CN IV) innervates the superior oblique muscle, which assists in downward and inward movement of the eye. Damage to this nerve can cause particular types of vertical diplopia but is less commonly associated with diplopia than the oculomotor nerve. Lastly, the abducens nerve (CN VI) controls the lateral rectus muscle, allowing the eye to move outward.