If you have experienced an ocular migraine you would probably say they are quite scary.
All of a sudden you may lose part of your vision. This can be a small blind spot or temporary blindness, typically occurring in only one eye.
Ocular migraines are different from regular migraine headaches, although the two may be closely related and are often confused as regular migraines can present in similar ways.
To best understand ocular migraines, it may be helpful to have some basic understanding of the underlying etiology of classic migraines.
Migraines occur through a combination of several processes.
Ultimately, special cells in the brain called neurons are hyper-excited, meaning they over-fire. The location of the headache pain depends on what part of the brain the neurons are located in.
As the excitation spreads, it triggers a response resulting in the blood vessels within the brain becoming dilated and inflamed.
The dilated, inflamed blood vessels put pressure on and therefore activate pain receptors within the brain, resulting in the debilitating pain known as a migraine headache.
Migraines frequently present with their own visual phenomenon called an aura. Roughly 20% of migraine suffers experience visual auras with their migraine attacks.
Auras occur when the neurons within the occipital cortex, the part of the brain responsible for visual processing, are hyper-excited.
Migraine visual auras typically appear as arced zig-zags of light that move across your vision. These zig-zags can be black and white or multicolored.
Migraine auras can also appear as geometric shapes of color, flashes of light that move across your vision, or stars in your vision.
Auras can be seen alone—meaning there is no major headache with the visual phenomenon, or can occur prior to the classic migraine pain.
Visual auras usually only last minutes to an hour or two and will move to affect different parts of your vision as the excited neurons spread across the occipital lobe.
One of the major differentiating factors between a migraine with aura from an ocular migraine is that an aura usually affects both eyes whereas an ocular migraine generally only affects one eye.
It is important to note that since migraines can affect different parts of the brain each time they occur, presentations of a migraine may be different each time. How a migraine presents all depends on the part of the brain affected.
The eyes are an extension of the brain. Therefore migraines can also occur, and be isolated to, solely the eyes.
The exact mechanism of action of an ocular migraine is unknown. However it is currently thought that ocular migraines occur similar to a classic migraine, but affects the neurons of the retina (the back most structure of the eye responsible for detecting light).
When the neurons of the retina are fired it can cause visual disturbances. Research has shown that during an ocular migraine there is a change in blood flow to the retinal arteries—retinal blood vessels dilate just as in classic migraines.
However, the retina is self-controlled and isolated from the regular blood supply of the brain, leading to questions as to the exact mechanism of this phenomenon.
It is also important to note that the retina does not contain pain receptors. Therefore, when the blood vessels of the retina dilate it does not cause pain—just a temporary visual disturbance.
The presentation of ocular migraines is also a little different than the presentation of a visual aura.
Ocular migraines present with a temporary loss of vision—this can be a small blind spot in the center of your vision or a blind spot that moves across your vision. A zig-zagged appearance of light may encircle the blind spot—but the telling sign that the phenomenon is an ocular migraine is that there is a blind spot/absence of vision.
The typical appearance of an ocular migraine is that an individual is reading something and suddenly he or she can only see a few letters out of the word. Blinking and straining does not clear up the word, but vision returns to normal within the hour.
Ocular migraines can last seconds to about an hour. The individual may experience a headache and light sensitivity post-ocular migraine, or the migraine can resolve completely without further problems.
Similar to classic migraines, ocular migraines have triggers—stress, lack of sleep, changes in diet, bright lights, and strong smells are some of the most common.
If you think you are having an ocular migraine it is best to take a break from what you are doing.
If you are driving—pull over and wait for vision to return to normal.
If doing a physical sport or activity, sit down and sip some water.
If you are out running errands, take a seat on a bench and wait for the phenomenon to pass.
Do not get behind the wheel of a vehicle, try to ride a bike, or operate machinery if you are experiencing an ocular migraine.
Be sure to talk with your eye doctor if you have been experiencing ocular migraines, especially if frequency increases. A neurological work up may be warranted or perhaps medications prescribed to help prolong the time between episodes.