Ocular migraines are caused by abnormal electrical activity in the brain or, less commonly, temporary spasms in the blood vessels of the retina. The term “ocular migraine” is used loosely to describe two distinct conditions: migraine with visual aura, where a wave of electrical activity sweeps across the brain’s visual processing area, and retinal migraine, where blood flow to one eye is briefly reduced. Both produce temporary visual disturbances, but they originate in different parts of the body and carry different levels of concern.
Two Conditions, One Name
The confusion starts with the name itself. When most people say “ocular migraine,” they mean the shimmering zigzag lines or blind spots that appear before or during a migraine headache. This is technically migraine with visual aura, and it affects both eyes because it originates in the visual cortex at the back of the brain. The visual disruption appears in one half of the visual field, which many people mistakenly interpret as affecting only one eye.
True retinal migraine is far rarer. It causes vision loss or visual disturbances in only one eye, driven by reduced blood flow within the eye itself. The International Headache Society defines retinal migraine as fully reversible monocular visual symptoms (flickering lights, blind spots, or temporary blindness in one eye) that spread gradually over at least five minutes, last between 5 and 60 minutes, and are accompanied or followed by a headache. If you cover one eye and the visual disturbance disappears, the problem is likely in the brain (visual aura). If it persists in one eye with the other covered, it may be a true retinal migraine.
The Brain Mechanism Behind Visual Aura
The most common type of ocular migraine, visual aura, is triggered by a phenomenon called cortical spreading depression. Think of it as a slow-moving electrical wave that rolls across the surface of the brain, sometimes described by researchers as a “brain tsunami.” This wave travels at just 2 to 5 millimeters per minute across the visual cortex.
The wave has two phases that explain exactly what you see. First, an intense burst of nerve cell activity sweeps outward. This hyperexcitation produces the positive visual symptoms: the bright zigzag lines, shimmering arcs, or flashing lights that gradually expand across your vision. Right behind that wave, nerve cells go quiet, their normal signaling temporarily suppressed. This suppression creates the negative symptoms: the dark or blank spots (scotomas) that trail behind the bright disturbances. As the wave moves across the visual cortex over 5 to 60 minutes, the visual disturbance appears to migrate across your field of vision before resolving completely.
What Causes Retinal Migraine
Retinal migraine involves the blood vessels inside the eye rather than the brain. The leading theory is vasospasm, a sudden, temporary narrowing of the retinal arteries that cuts off blood flow. The retinal circulation is unusual because it lacks the nerve supply that regulates blood vessels elsewhere in the body. Instead, it relies on a delicate chemical balance between substances that constrict blood vessels and those that relax them.
When this balance tips toward constriction, blood flow to the retina drops, causing flickering vision, blind spots, or brief blindness in one eye. Physical factors like blood pressure changes and metabolic factors like oxygen and carbon dioxide levels can influence this process. Once the spasm resolves, blood flow returns and vision recovers, typically within an hour.
Known Triggers
Ocular migraines share the same triggers as other migraine types, and they vary considerably from person to person. Several categories of triggers are well established:
- Food and drink: Chocolate, red and white wine, beer, aged cheeses, coffee cream, peanut butter, citrus fruits, canned foods, soy sauce, and foods containing red food dye have all been linked to migraine episodes. High carbohydrate intake and large meals can also act as triggers.
- Hormonal shifts: Fluctuations in estrogen, particularly around menstruation, pregnancy, and perimenopause, are among the strongest migraine triggers. This partly explains why women experience migraines three to four times more often than men.
- Sensory stimulation: Bright or flickering lights, prolonged screen time, and glare are common triggers for visual aura specifically.
- Stress and sleep disruption: Both acute stress and the letdown period after stress can provoke episodes, as can irregular sleep schedules or sleep deprivation.
- Physical factors: Dehydration, skipping meals, intense exercise, and changes in barometric pressure are frequently reported triggers.
Identifying your personal triggers usually involves keeping a detailed diary of what you ate, how you slept, your stress levels, and your environment in the hours before each episode. Most people have multiple triggers that stack together rather than a single culprit.
Who Gets Ocular Migraines
Migraine affects roughly 21% of women and 10% of men worldwide, and visual aura occurs in about one-third of those cases. The condition follows a bimodal pattern, with peaks around age 35 and again around age 50, then gradually decreasing with age. Adults between 20 and 50 are the most commonly affected group, though children and adolescents can experience them too.
Genetics play a significant role. Migraine runs in families, and identical twins are 1.5 to 2 times more likely to share the condition than fraternal twins. Large genetic studies have identified specific gene variants associated with migraine with aura, though the genetics are complex. Several rare inherited conditions involve migraine aura as a core feature, including familial hemiplegic migraine (caused by mutations in genes that control ion channels and nerve cell signaling) and a vascular condition called CADASIL that affects blood vessel walls in the brain. These rare forms illustrate how disruptions in either nerve cell excitability or blood vessel function can produce visual aura.
How Long Symptoms Typically Last
Visual aura from an ocular migraine usually builds gradually over 5 minutes or more and resolves within 60 minutes. A headache may follow, though some people experience the visual symptoms alone, sometimes called a “silent migraine.” Episodes lasting longer than 60 minutes happen occasionally and don’t necessarily indicate a problem, but visual disturbances lasting longer than 2 hours are considered rare and warrant investigation because they can, in uncommon cases, be associated with reduced blood flow to the brain. If visual symptoms persist beyond one week and other causes have been ruled out, it falls into a separate category called persistent aura without infarction.
Telling It Apart From Something Serious
The visual disturbances of an ocular migraine can feel alarming, especially the first time. A few key features help distinguish them from emergencies like retinal detachment or stroke.
Migraine flashes typically last up to 30 minutes, expand gradually from smaller to larger, appear in both eyes, and often form jagged geometric shapes that pulse in rhythm with your heartbeat. A blank spot may reduce your vision temporarily but improves as the flashing resolves. Floaters (dark spots drifting across your vision) are not typical of migraine.
Retinal tears or detachment, by contrast, produce flashes confined to one eye, often accompanied by a sudden shower of new floaters or a shadow creeping across your vision like a curtain. These symptoms don’t resolve on their own and require urgent evaluation. Stroke-related vision loss comes on suddenly without the gradual spread typical of migraine aura and usually doesn’t resolve within an hour. Any new or unfamiliar visual disturbance, especially one that doesn’t follow the typical migraine pattern you’ve experienced before, is worth getting checked with a complete eye exam.