Papilledema is an eye condition where increased pressure in or around the brain causes swelling of a portion of the optic nerve inside the eye. Increased intracranial pressure causes the optic nerve to swell where it enters the back of the eye. The fluid surrounding the brain is constantly produced and reabsorbed, maintaining sufficient intracranial pressure to help protect the brain if there is blunt head trauma. The anatomy of the optic nerve makes it a sensitive indicator of problems in the brain. This nerve connects the back of each eyeball and the retina to the brain. In the short distance between the brain and the eye, the entire surface of the optic nerve is bathed in cerebrospinal fluid. This fluid cushions the nerve from sudden movements. However, even slight increases in the pressure of this fluid, resulting from brain swelling, can compress the optic nerve in a "strangulating" manner all around its circumference. When this nerve is subjected to high pressure or develops self-inflammation, it can swell towards the back wall of the eyeball, causing papilledema.