What Are Ocular Migraines and What Causes Them
Ocular migraine (also called retinal migraine) is a rare condition characterized by repeated attacks of monocular (one-eye) visual disturbances—including scintillations, scotomas, or temporary blindness—that are fully reversible and associated with migraine headache. 1
Definition and Clinical Features
Ocular migraine is distinct from the more common "migraine with aura" where visual symptoms affect both eyes due to occipital cortex involvement. 2 True ocular/retinal migraine involves:
- Monocular transient visual loss (affecting only one eye) 3, 4
- Visual disturbances that are fully reversible 1
- Association with migraine headache (either during or following the visual symptoms) 1
- Must be diagnosed by exclusion after ruling out other causes of transient monocular visual loss 1
The hallmark diagnostic feature is unilateral visual loss associated with or followed by headache. 4 Ideally, an ophthalmologic examination during the actual attack provides the most diagnostic confirmation. 4
Terminology Clarification
The terms "ocular migraine," "retinal migraine," and "ophthalmic migraine" have been used interchangeably in the literature, creating confusion. 1 These should NOT be confused with "ophthalmoplegic migraine," which is an entirely different entity. 4
The more common condition that people colloquially call "ocular migraine" is actually migraine with aura, where visual symptoms occur in both eyes simultaneously. 2 In migraine with aura:
- Over 90% of affected individuals experience visual aura, classically as fortification spectra (zigzag patterns) 2
- Aura symptoms are transient focal neurological symptoms that usually precede but sometimes accompany the headache 2
- Each aura symptom typically lasts 5-60 minutes 2
- Visual symptoms affect both eyes (bilateral visual fields) due to occipital cortex involvement 5
Causes and Pathophysiology
The exact cause of true ocular/retinal migraine remains debated. It may be a misnomer, as its proposed etiology differs from our current understanding of typical migraine mechanisms. 1
Proposed Mechanisms:
- Vasospasm of retinal vessels leading to temporary ischemia 3
- Cortical spreading depression originating in the brainstem, which has been shown to activate the trigeminovascular system 5
- Genetic predisposition: Migraine has a strong genetic component with higher prevalence among first-degree relatives 2
For typical migraine with aura, functional neuroimaging has shown that brainstem structure activation precedes occipital cortex activation, challenging older vasogenic theories. 5
Can Dehydration Exacerbate Ocular Migraines?
Yes, dehydration can exacerbate migraine attacks, including those with visual symptoms. 6
Evidence for Dehydration's Role:
- Dehydration alone may cause headache, but more commonly exacerbates underlying primary headache disorders like migraine 6
- Maintenance of euhydration (proper fluid balance) is important in managing migraine triggers 6
- However, intravenous fluids administered for acute migraine attacks in emergency departments have NOT been shown to improve pain outcomes 6
Clinical Implications:
- Prevention of fluid losses is more effective than treatment with IV fluids once an attack has started 6
- Patients should be counseled to identify dehydration as a potential trigger and maintain adequate hydration as part of their migraine management strategy 2
- Dehydration can also mitigate secondary headaches dependent on fluid balance, such as orthostatic headaches 6
Important Caveat:
While maintaining hydration is reasonable preventive advice, the evidence does not support aggressive IV hydration as an effective acute treatment once a migraine attack has begun. 6 The focus should be on trigger identification and avoidance, including maintaining consistent hydration levels. 2