What causes ocular migraines?

Causes of Ocular Migraines

Ocular migraines are primarily caused by transient vasospasm of retinal or ciliary blood vessels, combined with neuronal hyperexcitability and cortical spreading depression affecting the visual pathways. 1, 2

Definition and Classification

Ocular migraines (also called retinal migraines) are characterized by:

• Fully reversible monocular visual disturbances lasting less than 1 hour
• Often followed by or occurring with migraine headache
• Most common in women of childbearing age with a history of migraine with aura 3

It's important to distinguish between:

• Retinal/ocular migraine: Truly monocular visual symptoms
• Migraine with visual aura: Bilateral (often appearing homonymous) visual disturbances

Pathophysiological Mechanisms

Several interrelated mechanisms contribute to ocular migraines:

1. Vascular Dysfunction:

   • Vasospasm of retinal or ciliary blood vessels
   • Altered blood flow regulation in ocular circulation
   • Transient ischemia to retinal or visual pathway structures

2. Neuronal Hyperexcitability:

   • Abnormal excitability of neurons in visual cortex
   • Cortical spreading depression (CSD) - a wave of neuronal depolarization followed by inhibition
   • Activation of trigeminal vascular system

3. Genetic Factors:

   • Family history is a significant risk factor
   • Multiple genetic variations affecting ion channels, neurotransmitter systems, and vascular regulation 4

Trigger Factors

Ocular migraines can be triggered by:

• Visual stimuli - particularly striped patterns that cause "pattern glare" 5
• Environmental factors - bright or flickering lights, screen time
• Stress and fatigue 5
• Hormonal changes - especially in women
• Caffeine consumption or withdrawal
• Certain medications - including antihistamines, antidepressants, and oral corticosteroids 6

Associated Conditions

Several conditions are associated with increased risk of ocular migraines:

• Migraine headaches - especially migraine with aura
• Vasospastic disorders - including Raynaud's phenomenon
• Cardiovascular risk factors - hypertension, diabetes
• Dry eye syndrome - can exacerbate symptoms 7, 6
• Inflammatory conditions affecting the eye

Clinical Presentation

Typical presentation includes:

• Monocular visual disturbances (scintillating scotomas, partial or complete visual loss)
• Episodes lasting less than 1 hour (typically 5-30 minutes)
• Followed by or accompanied by migraine headache (though headache may be absent)
• Fully reversible symptoms, though some cases may progress to permanent visual defects 3

Diagnostic Considerations

When evaluating ocular migraines, it's essential to:

• Confirm the truly monocular nature of symptoms (test each eye separately)
• Rule out other serious causes of monocular vision loss:
  • Retinal artery or vein occlusion
  • Optic neuritis
  • Amaurosis fugax due to carotid disease
  • Retinal detachment

Management Approaches

Management should focus on:

1. Trigger identification and avoidance:

   • Reduce exposure to visual triggers like striped patterns 5
   • Manage screen time and use blue-light filtering glasses
   • Maintain regular sleep patterns

2. Lifestyle modifications:

   • Stress reduction techniques
   • Regular exercise
   • Consistent meal timing
   • Adequate hydration

3. Visual comfort measures:

   • Colored filters (particularly blue-to-green spectrum) may help reduce pattern glare 5
   • Preservative-free lubricants for associated dry eye 6

4. Pharmacological options (for frequent or severe episodes):

   • Migraine preventive medications
   • Acute treatments during episodes

Conclusion

Ocular migraines result from a complex interplay of vascular dysfunction, neuronal hyperexcitability, and genetic predisposition. Visual stimuli are particularly important triggers, and management should focus on trigger avoidance and symptom control. While typically benign and self-limiting, persistent or atypical symptoms warrant thorough evaluation to rule out more serious conditions.