What is the primary function of the optic nerve?

The primary function of the optic nerve is to carry impulses of sight from the retina to the brain. The optic nerve is crucial for vision, consisting of over a million nerve fibers that transmit visual information processed by the retina. When light enters the eye, it is converted into electrical signals by photoreceptor cells in the retina, which then travel along the optic nerve to reach the brain. This pathway allows the brain to interpret these signals as visual images, enabling us to see.

The other options refer to different functions that are not specific to the optic nerve. Regulating eye movement is primarily managed by extraocular muscles and cranial nerves responsible for motor control. Control over the focus of the eye, allowing us to see objects clearly at various distances, involves the lens and ciliary muscles, not the optic nerve. The protection of the eye from harmful light is more associated with structures like the eyelid and the cornea, which help shield the eyes from excessive brightness and harmful UV rays.