According to Healthline, the function of the oculomotor nerve is to control the eye. This nerve has two components, one of which controls visual tracking and the other which controls the eye's reflexes to light.
The oculomotor nerve is made up of two parts, Healthline says. The somantic motor component deals with the muscles in the eye and the eyelid so that the eyeball can move and track objects. The visceral motor component deals with the automatic responses of the eye and surrounding muscles. For example, it aids in the pupillary light reflexes when the pupil dilates because of light intensity, as Wikipedia explains.
Many conditions and diseases can damage the oculometer nerve and result in problems, according to Healthline. For instance, oculomotor nerve palsy occurs when the nerve becomes paralyzed as a result of multiple sclerosis, brain cancer, diabetes, trauma to the eye or pressure on the brain. About.com explains that elevated intracranial pressure can cause double vision and what is known as a "blown pupil," or a pupil which is no longer able to constrict. A blown pupil is often a sign of neurological damage.
The oculomotor nerve works in concert with the optic nerve, the trochlear nerve, the abucens nerve and the facial nerve when it comes to operating the eyes, according to About.com.