The optic nerve is the bundle of axons that carries visual information from the retina to the brain. Each nerve contains roughly one million fibers arising from the ganglion cells of the retina.

The axons exit the eye at the optic disc, creating the blind spot where there are no photoreceptors. The two optic nerves meet at the optic chiasm, where fibers from the nasal half of each retina cross to the opposite side. Beyond the chiasm the pathways continue as the optic tracts to the lateral geniculate nucleus of the thalamus and then to the visual cortex. Some fibers also reach midbrain nuclei that control pupil reflexes and eye movements.

Damage to the optic nerve—from glaucoma, inflammation, or trauma—produces vision loss that cannot be corrected by lenses. The pattern of loss depends on where along the pathway the damage occurs. Because the nerve is part of the central nervous system, it does not regenerate readily after injury.

Every visual signal that reaches the brain travels first along the optic nerve.