The Normal Eye - Optic Nerve
At its entry into the retina, the optic nerve is referred to as the optic disc or optic nerve head. This is also the point of entry for the central retinal artery and vein, which form the retinal vasculature.
Functionally, the optic nerve transmits the information gathered by the neurosensory retina to the brain along approximately 1.2 million axons. While most of the axons are concerned with vision, some provide a pathway for the pupillary light reflex while others relay general responses to light (e.g. blinking, eye movement, neck muscles).
Eye reflexes are often used to assess patient condition. For example, pupillary reaction is observed by flashing light into the eye; this normally results in constriction of the pupil. An abnormal pupil accommodation reflex when focusing on different objects may be indicative of a pathological condition (e.g. syphilis).