Glaucoma as a Neurological Disease

The retinal ganglion cells (RGC) and their axons that form the optic nerve are anatomically and developmentally an extension of the central nervous system (CNS). In fact, the optic nerve should not be considered a 'nerve' but rather a CNS white matter 'tract' containing glia of the white matter of the brain and spinal cord namely oligodendrocytes, astrocytes, and microglia, rather than Schwann cells. The optic nerve is also surrounded by meninges like other white matter tracts. It is not surprising that pathological processes that affect the optic nerve, therefore, demonstrate changes in the brain. However, many ophthalmologists and members of the lay public have focused on glaucoma as exclusively a disease of the eye and have been surprised when pathological abnormalities have been identified in the part of the afferent visual pathway that extends into the brain. This view has been pervasive because the recognized risk factors associated with glaucoma have been ocular: intraocular pressure, corneal thickness, abnormalities of the trabecular meshwork and the angle. Many investigators have highlighted that this perception has resulted in lost opportunities.