Posterior segment changes in glaucoma

In humans, the optic nerve primarily transmits visual information from the retina to the lateral geniculate nucleus. Afferent fibers of the optic nerve also synapse in accessory central nervous system (CNS) centers such as the Edinger-Westphal nucleus, which controls pupillary reflexes. The optic nerve originates from axons of the retinal ganglion cells (RGCs) in the innermost cell layer of the retina. These un-myelinated axons then course posteriorly in bundles of the nerve fiber layer and meet at the rim of the optic nerve head. The bundles then bend approximately 90° and pass through the lamina cribrosa, a circular, fenestrated connective tissue extension of the sclera, into the orbit where the fibers become myelinated. For 20mm to 30mm behind the eye, the nerve has a sinuous course to allow movement of the globe. The intra-orbital optic nerve is covered by an outer dura mater and an inner arachnoid sheath, both of which are attached to the sclera around the lamina cribrosa. The 10mm long intra-cranial portion begins at the optic foramen, through which the optic nerve fibers then pass posteriorly and medially to the optic chiasm where they partially decussate. The mixed fibers continue in the optic tracts, to terminate primarily in the lateral geniculate nuclei.

Duke Scholars

Author Stuart James McKinnon Ophthalmology, Glaucoma