The oculomotor nerve is the third cranial nerve responsible for controlling most of the eye's movements. It innervates several muscles, including the superior rectus, medial rectus, inferior rectus, and inferior oblique, which help in moving the eye in different directions. Additionally, it plays a crucial role in adjusting the size of the pupil and maintaining an open eyelid. This nerve originates in the midbrain and travels to the orbit, where it branches out to the eye muscles. Damage to the oculomotor nerve can lead to symptoms such as double vision, drooping eyelids, and difficulty focusing, highlighting its importance in visual function.