Migraine aura

How it works

An aura starts as a small blind or flickering spot near the centre of vision. Over minutes it spreads outward. Its edge becomes a zigzag of bright, shimmering lines, often shaped like a C or a crescent². Behind the edge is a blank patch. The whole thing lasts 5 to 60 minutes and then fades¹. It looks the same with either eye closed, because it is in the brain and not in the eye². Other auras exist: tingling that creeps up an arm, or trouble finding words¹.

The cause is cortical spreading depression. A wave of intense neuron activity, followed by silence, moves across the visual cortex at 3 to 6 mm per minute³. Where the wave is, you see flicker. Behind it, where the neurons are quiet, you see a blank³. The slow speed of the wave explains the slow growth of the pattern.

About 3% of the general population have migraine aura⁴. About a quarter of people with migraine get aura⁴. In some people the aura comes with no headache at all. This is more common after the age of 50¹. The name “ocular migraine” is used loosely, so doctors prefer “migraine with aura”.

Is it a problem?

Usually no. An aura does not damage the brain or the eyes. It passes within the hour. Do not drive during it.

Get a first episode checked, because a doctor should confirm that it is an aura and not something else. Go to emergency care if it lasts more than an hour, starts suddenly at full size rather than spreading, or comes with weakness on one side, trouble speaking, or the worst headache of your life¹. Those can be a stroke, which looks similar but begins all at once.

Once a doctor has confirmed typical aura, repeat episodes do not need emergency care. Tell your doctor if the pattern changes. If you use a combined hormonal contraceptive, mention the aura, because the two together raise stroke risk⁴.

History and culture

The zigzag edge is called “fortification spectra” because it looks like the walls of a star-shaped fort seen from above². The visions described by the 12th-century abbess Hildegard of Bingen, with rings of shimmering light, may have been migraine auras².