Migraine is most often understood to be a severe headache and a neurovascular disorder that occurs primarily on one side of the head, which is accompanied by vomiting, severe pain and light and sound sensitivity. (1) However, the term ocular migraine is different from migraine experienced by a majority of the people and it is most commonly used to describe these two situations:
- Migraine with an aura:
A migraine with an aura is the condition which affects the vision of the eye before the migraine headache starts. It usually happens in both eyes. This type of migraine causes both headache and vision impairments. These types of migraine usually happen due to the pain in the back of the head, in the visual cortex which causes aura in both eyes. The aura may last for an hour, which is then followed by a headache.
- Retinal migraine:
Ocular migraine is most commonly termed as “retinal migraine”. Ocular migraine is a rare condition that affects vision, resulting in vision impairments in only one eye. What differentiates this type of migraine from classical migraine is that this sort of ocular migraine happens without throbbing pain and severe headache.
What is an aura?
A visual aura is a blind spot that grows over time. These auras can be of different types
- Blind spots
- Shimmering lights
- Zigzag lights
- Blinding lights
- Heat wave
An aura usually goes away in an hour, and the vision is restored to normal. As there can be various reasons behind an aura it is best to visit an eye specialist to identify the underlying cause behind the aura. It is also necessary because in case the patient is experiencing an Ocular Migraine, any complication can result in permanent vision impairment.
Mechanism of Ocular Migraine:
There are many hypotheses which discuss the mechanism behind Ocular Migraine and all are very controversial among doctors. During an ocular migraine the cranial nerve V comes into action and releases neuropeptides. These neuropeptides cause painful neurogenic inflammation which leads to vasodilation causing disturbance of the blood flow at the back of the retina. According to a study a dilation of both the middle meningeal and middle cerebral arteries was observed. But this theory cannot be entirely accepted because some researchers believe that vasodilation is an epiphenomenon and not a causative agent behind ocular migraine. (2)
Ocular Migraine by numbers:
Ocular migraine is a very rare condition and since little statistical data and research has been done with the specification of Ocular Migraine, no clear answer about its prevalence can be traced. However, according to a survey 20-25 percent of people suffering from migraine experience visual impairment. The ocular migraine most often starts in the first decade of life and gets worse when the patient reaches 40 but only 50 percent of people with retinal migraine experience complete loss of vision in one eye. According to a research 29 percent of people with ocular migraine were experiencing classical migraine prior to ocular migraine. Like all the other migraine this migraine is also more prevalent among women than in men.