Papilledema is optic disc swelling that is caused by increased intracranial pressure. The swelling is usually bilateral and can occur over a period of hours to weeks. Papilledema occurs in approximately 50% of those with a brain tumour.

As the optic nerve sheath is continuous with the subarachnoid space of the brain (and is regarded as an extension of the central nervous system), increased pressure is transmitted through to the optic nerve and this leads to edema of the cells of the optic disc.

Checking the eyes for signs of papilledema should be carried out whenever there is a clinical suspicion of raised intracranial pressure. Because of the (rare) possibility of a brain tumor or pseudotumor cerebri, both of which can increase intracranial pressure, this examination has become common for patients suffering from headaches. The hallmarks of papilledema are:

• swelling of the optic disc
• poorly defined disc margins
• hemorrhage of disc nutrient vessels