Compartment syndromes of the optic nerve and open-angle glaucoma.

A compartment is a space or volume that is separated from its environment. The cause for separation can be manifold. It can be expressed as a difference [INCREMENT] in parameters, such as size, area, volume, color or pressure. The border of a compartment can be rigid or flexible (compliance). The optic nerve is located within the subarachnoid space and is covered by the dura mater, the arachnoid and the pia mater that cover the brain as well. As is the brain, the optic nerve is bathed in cerebrospinal fluid (CSF). Optic nerve compartmentalization has been demonstrated in papilledema, anterior ischemic optic neuropathy, posterior ischemic optic neuropathy, and normal tension glaucoma. Anatomically the optic nerve can be described as located in a cul de sac with a steady inflow of CSF from the pituitary cistern via the optic canal. This specific anatomy raises questions concerning the mechanism of CSF recycling from the confined perioptic space.