Figure 1.

For this study, the optic nerve was divided into 5 segments, as depicted: intraorbital [extending from the optic bulb to the start of the optic canal], canalicular [the portion of the nerve that lies within the optic canal], pre-chiasmal [begins at the exit of the optic canal intra-cranially extending to the chiasm], chiasmal [across the chiasm], and optic tracts [posterior to the chiasm] (2); there were 9 segments in total. (Sketch from Wikimedia Commons.)