The optic nerve which, as we have seen, is ontogenetically, morphologically and functionally part of a tract of the central nervous system extending from the ganglion cells of the retina to the mid-brain, runs from the eye to the chiasma. Since it is a central nervous path, it is organized anatomically like the white matter of the cord or brain : there are no sheaths and cells of Schwann and instead of a endoneurium there are true reticular connective tissue framework characteristic of the cerebro-spinal nerves, and it is clothed by the coverings of the brain - the dura, the arachnoid and the pia.
The optic nerve varies considerably in length, even between the two eyes of the same individual and contains five types of fibres : visual, pupillary, efferent, photostatic and autonomic.