THE OPTIC NERVE (II)

The optic nerve mediates the visual sense and is in fact a brain tract connecting the retina with the diencepha­lon (from which it originated). The intracranial part of the nerve extends from the optic chiasm (Figure 8-19/7), where varying proportions of the fibers decus­sate (p. 299), to the optic foramen at the apex of the orbital cone; the intraorbital course is described else­where (p. 345) (see Figure 9-17/9). The optic nerve is also enclosed within extensions of the meninges, and the dura blends with the sclera where the nerve joins the eyeball. Section of the nerve obviously results in blindness of that eye.