Ocular Migraine and Visual Aura: Symptoms, Triggers, Red Flags

It often starts with a small, flickering blind spot that makes it hard to read a word or see someone's face. Over the next few minutes it grows into a shimmering, zigzag arc of light, sometimes with bright colours, slowly drifting outwards across your vision before fading away within an hour. For many people a headache follows; for others it does not. This is the experience commonly called an ocular migraine, and although it can be frightening, especially the first time, it is usually harmless.

The term ocular migraine is used loosely, though, and covers two different conditions: the common migraine with visual aura, which comes from the brain, and the much rarer retinal migraine, which affects one eye. Importantly, some symptoms that resemble migraine can be signs of a transient ischaemic attack (TIA, or mini-stroke) or a stroke, which need emergency care. This guide explains the differences, typical symptoms, triggers, treatment and how to recognise the warning signs.

What is migraine aura?

Migraine is a common neurological condition. According to the World Health Organization, it is one of the leading causes of disability worldwide. About a quarter to a third of people with migraine experience aura, a set of temporary neurological symptoms that typically come before or with the headache.

Visual aura is the most common type. It is thought to be caused by a slow wave of altered electrical activity that spreads across the visual cortex at the back of the brain, called cortical spreading depression. Because the disturbance travels across the brain at a few millimetres per minute, the visual symptoms gradually move and expand. Since the visual cortex processes information from both eyes, the aura appears in the same part of the visual field in both eyes, even though people often feel it is in one eye.

Typical visual aura symptoms

• A scintillating scotoma: a shimmering, flickering blind spot, often with a bright, zigzag edge like a fortification wall (fortification spectra).
• Zigzag lines or flashing lights that move or expand across the visual field.
• Blind spots or patchy vision, sometimes making half a face or part of a word disappear.
• Heat-haze or wavy distortion, as if looking through water.
• Less commonly: tunnel vision, seeing things as larger or smaller, or a mosaic effect.

Aura usually builds gradually over at least 5 minutes and lasts between 5 and 60 minutes. Some people also experience other aura symptoms, such as pins and needles that spread up an arm and into the face, or difficulty finding words. These need a careful medical assessment, especially the first time, because they overlap with symptoms of stroke.

Aura with and without headache

In many people, aura is followed within an hour by a throbbing headache, often on one side, with sensitivity to light and sound, nausea or vomiting. However, aura can also occur on its own, which is sometimes called silent migraine or typical aura without headache. This is more common in people over 50, who may have had migraine headaches in their youth that later changed pattern.

Retinal migraine

Retinal migraine is a rare condition in which temporary visual disturbance, such as dimming, blind spots, flashing lights or complete loss of vision, affects only one eye, usually followed by headache. It is thought to involve temporary narrowing of blood vessels in the retina or behind the eye. Attacks typically last less than an hour, and vision returns to normal between episodes.

Because many serious conditions can also cause temporary vision loss in one eye, retinal migraine is a diagnosis of exclusion. Doctors must first rule out problems such as a blockage in the arteries supplying the eye, a clot from the carotid artery, giant cell arteritis or problems with the optic nerve, particularly in people over 50 or with cardiovascular risk factors.

How to tell whether one eye or both are affected

During an episode, cover one eye and then the other. If the disturbance stays in the same place in your vision whichever eye is open, it is coming from the brain and is likely aura. If it disappears completely when you cover one eye, it is coming from that eye. This simple check gives your doctor valuable information.

When visual symptoms could be a TIA or stroke

A transient ischaemic attack happens when blood flow to part of the brain or eye is briefly interrupted. Symptoms resolve, often within minutes, but a TIA is a major warning sign of a future stroke, and the risk is highest in the following days. Visual symptoms of TIA or stroke can include sudden loss of vision in one eye (amaurosis fugax), sudden loss of half the visual field in both eyes, or sudden double vision.

Features that suggest a TIA or stroke rather than migraine include:

• Symptoms that start suddenly, at full intensity, rather than spreading gradually.
• Negative symptoms (darkness, loss of vision) without positive ones (shimmering lights).
• Sudden vision loss in one eye, especially described as a curtain coming down.
• A first-ever episode in someone over 50, or in someone with high blood pressure, diabetes, high cholesterol, heart rhythm problems such as atrial fibrillation, or a smoker.
• Weakness, numbness, facial drooping, slurred speech or confusion occurring at the same time.

People with migraine with aura have a modestly increased risk of stroke, particularly women who smoke or take combined oestrogen-containing contraceptives. If you have migraine with aura, discuss contraception and smoking with your doctor.

Other conditions that can mimic ocular migraine

• Retinal tear or detachment: flashes and new floaters in one eye, sometimes with a shadow; see our guides to floaters and flashes and retinal detachment.
• Giant cell arteritis: in people over 50, transient vision loss with scalp tenderness, jaw pain when chewing or new headaches; an emergency because it can cause permanent blindness.
• Optic neuritis: blurred vision in one eye with pain on eye movement, developing over days.
• Raised pressure in the skull: brief greying out of vision on standing or bending, with headaches.
• Occipital seizures: brief, often coloured, circular visual phenomena.

Common migraine triggers

Migraine triggers vary greatly between individuals, and often several factors combine to tip the balance. Commonly reported triggers include:

Keeping a headache diary for a few months, noting attacks, sleep, food, menstrual cycle and stress, can reveal personal patterns. Rather than trying to avoid every possible trigger, which can be restrictive, focus on regular sleep, meals, hydration and stress management. Our guides on sleep and eye health and stress and the eyes offer practical tips. Uncorrected vision problems and prolonged screen use can cause eye strain headaches, which are different from migraine but may coexist; see eye strain and headaches.

Managing an episode

Visual aura usually passes within an hour. During an episode:

• Stop driving or operating machinery and wait in a safe place until vision returns completely.
• Rest in a quiet, dimly lit room if possible.
• If you usually get a headache afterwards, take the pain relief or migraine treatment your doctor has advised early in the attack.
• Note the time, how long it lasts, what you see and whether one or both eyes are affected.

Treatment and prevention

Treatment is individualised and guided by a doctor. Acute treatments include simple painkillers and anti-inflammatory medicines, anti-sickness medicines and specific migraine medicines such as triptans, which are often taken once the headache phase begins. Newer drug classes, including gepants, are available in some countries. Your doctor will decide which medicines are suitable, especially if you have cardiovascular disease, because some migraine medicines narrow blood vessels.

If migraines are frequent or disabling, preventive treatment may be recommended. Options include several classes of daily tablets, newer injectable or oral medicines targeting the CGRP pathway, and botulinum toxin injections for chronic migraine. Non-drug approaches such as regular aerobic exercise, relaxation techniques, cognitive behavioural therapy and good sleep routines also have evidence of benefit. Avoid taking painkillers on many days a month, as this can lead to medication-overuse headache.

When to see a doctor

See your GP or a doctor if you have visual disturbances for the first time, if your pattern of attacks changes, if attacks become more frequent, or if you need painkillers often. Have an eye examination to rule out eye causes, particularly if you are unsure whether one or both eyes are affected. Our guide to eye examinations explains what to expect.