Papilledema and Optic Nerve Disorders

Papilledema is optic disc swelling caused specifically by raised intracranial pressure (ICP). Pressure in the cranial subarachnoid space is transmitted along the optic nerve sheath to the optic nerve head. This obstructs axoplasmic flow at the lamina cribrosa, so axons swell and the optic disc becomes elevated with blurred margins. The term is not interchangeable with *optic disc oedema*. Optic neuritis, anterior ischaemic optic neuropathy, infiltration, and optic disc drusen can all produce an abnormal-looking disc without raised ICP. Calling every swollen disc “papilledema” is unsafe because it sends the assessment toward the wrong emergency pathway. Papilledema is usually bilateral because raised ICP affects both optic nerve sheaths. It may be asymmetric, but a clearly unilateral swollen disc should prompt consideration of a local optic nerve disorder first. Early papilledema can look less serious than it is. Central visual acuity is often intact because the macula is initially spared. The earliest functional change is commonly enlargement of the physiologic blind spot or peripheral, especially nasal, visual field loss. A person may read the acuity chart well yet be developing vision-threatening...