What are ocular migraines?

You may have heard the term ‘migraine with aura’, but are ocular migraines the same thing?

Neurovascular headaches, migraines are a highly uncomfortable experience for anyone who suffers them ⁽¹⁾. An ocular migraine, also known as retinal migraine or ophthalmic migraine, is a rare condition estimated to affect about 1 out of every 200 individuals who experience migraine headaches. This type of migraine causes characteristic transient vision loss or blindness in one eye (monocular blindness) for a short period of time (normally less than 1 hour). Bouts of impaired visual functionality may occur repeatedly, often preceding or accompanying a severe headache (throbbing one-sided / unilateral migraine), and sometimes waves of nausea too.  An ocular migraine may, however, occur without any headache at all.

Migraines in general can sometimes cause visual disturbances. This is referred to as migraine with aura (formerly known as a classic migraine) which means that the migraine presents with neurological symptoms. This typically involves blind spots, zigzagging patterns (or wavy lines), shimmering spots (also referred to as ‘seeing stars’) and flashing light in a person’s field of vision. Such disturbances and sensation changes are characteristic of migraine with aura, but unlike the symptoms experienced during an ocular migraine, generally affect both eyes.

While the characteristic symptoms of migraine auras are primarily visual in nature, they can also cause impairments and sensation changes relating to hearing, smell (sensitivity), speech (difficulties with speaking clearly), and even a progressing numbness or tingling in the facial area or limbs (arms and legs). These symptoms interfere with a person’s ability to function normally making it difficult to communicate, read, perform certain tasks or drive.

Initial aura symptoms generally occur before the onset of the headache and typically don’t last for a long period of time.

A person experiencing an ocular migraine will likely go through temporary visual disturbances (aura) or even blindness in one eye just before symptoms of headache arise. Unlike in migraines with aura, these symptoms may continue even once the headache sets in and pain is generally localised behind the affected eye instead of being more spread out across the eyes and head. Visual disturbances do eventually resolve on their own and the affected person will recover and be able to resume normal activity following an ocular migraine attack.

It has been noted, however, that an ocular migraine attack may not necessarily happen only once. The frequency of these attacks can vary, and depend on a person’s individual overall condition. Some ocular migraine sufferers experience these types of headache attacks every few months.

Generally, retinal migraines do not cause any damage and are not an indication of any serious eye problems. There is a small risk that some degree of damage to the retina and blood vessels may occur due to reduced blood flow, and it is thus wise to seek medical evaluation should these types of migraine be experienced.

During a medical consultation relating to an ocular migraine, a doctor may wish to check for, diagnose or rule out some of these underlying conditions, which can include:

• Eye disease
• Carotid artery disease (wherein plaque build-up within the walls of the carotid arteries, known as arteriosclerosis, causes narrowing of the blood vessels that transport blood from the heart to the brain)
• Arterial dissection (a tear in arteries supplying blood to the brain)
• Arteriovenous malformation (tangling of veins or arteries in the brain)
• Cerebral vasculitis (inflammation of the blood vessel walls in the brain and/or spinal cord)
• Head injuries
• Seizures
• Structural abnormalities relating to the head, spine or neck
• Spinal fluid leak
• Stroke (haemorrhagic or ischemic – either a ruptured or blocked artery in the brain)
• Aneurysm (artery widening or bulging as a result of weakness in the wall lining of a blood vessel)
• Inflammation in the brain (causing conditions such as meningitis, or encephalitis)
• Hydrocephalus (excess cerebrospinal fluid accumulation in the brain)
• Trigeminal neuralgia (chronic pain which affects the trigeminal nerve in the face)
• Brain tumours
• Possible exposure to a toxic substance (a withdrawal effect from a substance can also result in symptoms)

Reference

^{1. Migraine.com. 17 December 2010. Expert Answer: Migraine pathophysiology: https://migraine.com/blog/vascular-and-neurovascular-theories-pertaining-to-migraine-pathophysiology [Accessed 25.10.2017]}