Papilledema is swelling at the spot where the optic nerve exits the eyeball, usually as the result of increased intracranial pressure. It almost always appears in both eyes at once. It is a medical emergency that requires immediate medical attention and, in many cases, immediate intervention to prevent loss of sight. A full examination by an opthamologist is almost always called for. A physician should check for it in any patient with increased intracranial pressure or when they present with a sudden onset headache.