Ocular migraines are caused by sudden, temporary changes in blood flow to the retina or by waves of abnormal electrical activity spreading across the brain’s visual processing area. The term “ocular migraine” is used loosely to describe two related but distinct conditions: retinal migraine, which affects only one eye, and migraine with visual aura, which affects both eyes. The underlying causes overlap, but the specific mechanisms differ in important ways.
How Blood Flow Changes Cause Retinal Migraine
A true retinal migraine (also called an ocular migraine in clinical settings) involves temporary vision loss or visual disturbances in one eye only. The primary cause is vasospasm, a brief but intense narrowing of the small arteries that supply blood to the retina. This cuts off oxygen to retinal cells, producing symptoms like flickering lights, blind spots, or even complete but temporary blindness in the affected eye.
Retinal vasospasm is rare, occurring in roughly one in 200 people who get migraines. The retina’s blood vessels lack the nerve supply that controls vessel width elsewhere in the body. Instead, they rely on a self-regulating system that balances two opposing chemical signals: one that constricts blood vessels and one that relaxes them (nitric oxide). When that balance tips toward constriction, a spasm can occur. Physical factors like blood pressure, oxygen levels, and pH also influence the process, which is why triggers can vary so widely from person to person.
The good news is that these episodes are almost always fully reversible. Despite how alarming they feel, there are no convincing reports of permanent vision loss directly caused by retinal migraine.
How Brain Activity Causes Visual Aura
The more common type of “ocular migraine” is actually migraine with visual aura, which affects vision in both eyes. This one originates not in the eye but in the brain. A slow wave of hyperexcitation spreads across the visual cortex (the area at the back of the brain that processes sight), followed immediately by a period of reduced blood flow and suppressed nerve activity. Researchers call this phenomenon cortical spreading depression.
Think of it like a power surge followed by a blackout rolling across a neighborhood. As the wave moves, it produces the classic visual symptoms: shimmering zigzag lines, expanding blind spots, or flashing lights that drift across your visual field over several minutes. The gradual spread of the wave is why aura symptoms typically build slowly over five or more minutes rather than appearing all at once. Most visual auras last between five minutes and one hour.
Increased excitability in the brain’s nerve cells, fluctuations in normal brain wave patterns, and random neural “noise” all contribute to triggering these waves. People who get migraines with aura appear to have a lower threshold for this cascade to start, meaning their brains are more easily tipped into the spreading wave pattern.
One Eye vs. Both Eyes
The distinction between retinal migraine and migraine with aura matters because the causes sit in different parts of the body. Retinal migraine originates in the blood vessels of a single eye. Migraine with aura originates in the brain and affects the visual field of both eyes, even though it can sometimes feel like only one eye is involved. If you close one eye during an episode and the disturbance is still visible through the other, the cause is in the brain, not the retina.
There are other practical differences. Visual symptoms in retinal migraine tend to be shorter. The headache that follows typically concentrates behind the affected eye, while migraine with aura produces pain that spreads more broadly across the head.
Genetic Factors
Migraine is a brain disorder with a strong genetic component. Common forms of migraine, both with and without aura, have a polygenic makeup, meaning many genes each contribute a small amount of risk rather than a single gene being responsible. Genome-wide studies have identified over a dozen genes involved in both nerve signaling and blood vessel function, which aligns with the two main mechanisms described above.
If your parents or siblings get migraines, your risk is significantly higher. Rare inherited conditions that involve retinal blood vessel problems exist as well, though these are distinct from typical ocular migraine and usually present with additional neurological symptoms.
Common Triggers
Having a genetic predisposition sets the stage, but individual episodes are usually sparked by triggers. These vary from person to person, and researchers caution that the relationship between triggers and attacks isn’t always straightforward. Still, several categories come up consistently in large studies.
Stress is the most frequently reported trigger, cited by roughly 59% of migraine sufferers in clinical surveys. Strong odors, particularly perfume, cigarette smoke, and cleaning products, rank second at about 48%. Light exposure is another well-documented trigger. People with migraines are more sensitive to light not only during attacks but between them, and studies in northern Norway found that nearly 12% of migraine sufferers experienced more attacks during the midnight-sun season, when daylight is constant.
The list of dietary triggers is long. The most commonly cited include:
- Alcohol, especially red wine and beer
- Aged or fermented foods like cheese and processed meats
- Stimulants and additives like caffeine, MSG, and aspartame
- Other foods including chocolate, nuts, citrus fruits, and fatty foods
Weather and atmospheric pressure changes are also frequently reported, though the mechanism behind this link remains unclear.
Who Gets Ocular Migraines
Migraine in general affects women far more than men, and this holds true for ocular migraines as well. Before puberty, boys and girls develop migraines at roughly equal rates (around 2 to 5%). The gap opens at puberty: by ages 13 to 15, prevalence is 6.4% in girls compared to 4.0% in boys. Hormonal changes are a major driver of this difference.
Migraine incidence peaks around age 35, when it affects 25 to 30% of women and about 8% of men. A second, smaller peak occurs around age 50. After that, frequency generally declines with age, dropping more noticeably after 75. For women with menstrually related migraines, the usual correlation between light exposure and attack frequency doesn’t seem to apply, suggesting that hormonal triggers can override environmental ones.
Why Episodes Happen When They Do
One of the most frustrating aspects of ocular migraines is their unpredictability. You might eat the same food or experience the same stress level dozens of times without an episode, then suddenly have one. This is because migraine threshold fluctuates. Your brain’s susceptibility to an attack shifts throughout the day, the menstrual cycle, and even the season. A trigger that falls below your threshold on most days might push you over it when you’re sleep-deprived, dehydrated, or dealing with hormonal shifts. It’s the accumulation of factors, not a single cause, that typically tips the balance.
Keeping a simple log of your episodes, what you ate, how you slept, your stress level, and where you are in your cycle if applicable, can help you identify which combinations of factors put you most at risk. Over time, patterns often emerge even when individual triggers seem inconsistent.