Symptoms of ocular migraine
Ocular migraine is common phrase that means the same as the proper term migraine visual aura.
Symptoms of migraine visual aura can come in several forms.
One large study of 161 Danes with migraine aura found that 82% of visual symptoms developed over 5-30 minutes, and 69% were completed within a further 5-30 minutes.
About 3% of migraine aura seems to appear rapidly, and 4% had prolonged visual aura, which evolved over more than an hour and persisted for more than the second hour.
These rapid or prolonged symptoms need very careful assessment as there is a small chance of finding an underlying cause in very rapid or very prolonged aura cases.
Most people report symptoms of ocular migraine in one eye only.
The Danish survey was 69% one-sided and 31% both eyes. However, the symptoms are often present in both eyes, and you can only know this if you cover one eye at a time.
Very often the visual symptom will occupy one half the field of vision in one eye, but only a fraction of field of vision in the other.
Unless you cover the more severely affected eye and have a careful look, you will easily miss the involvement of the lesser affected eye.
Descriptions of Migraine Visual Aura / Ocular Migraine
The most common type of visual aura is a zig-zag-shimmering geometric shape.
These often start at the middle of the field of vision and then spread over 5-30 minutes to the edge of field of vision.
It often leaves a central area of visual loss called a scotoma.
A scotoma is usually a pale area of visual loss.
If you have a scotoma and look at someone's face, you can see their hair, chin and ears, but not their mouth or nose.
The symptoms of ocular migraine also include abnormal perception of vision.
These are often reported by children, but adults, particularly migraine artists have described many of them in detail:
- Objects looking too big - called macropsia
- Objects looking too small - called micropsia
- Seeing multiple copies of objects - polyopia
- Inversions - things looking upside down
- Seeing objects appear tilted or rotated
- Illusory Splitting - this is where objects or faces appear split or fractured. The fracture or fissure is usually in the form of a geometric shape
- Mosaic Illusion or Fragmentation - where things look like you are viewing them through broken glass
- Geometrisation - normal objects appear to have lost normal contour and have "squared-off"
- Corona Phenomenon - a rim of light appears around the edge of objects or around the edge of a migraine aura geometric shape.
- Objects looking too far away - teleopsia
- Objects looking too near - pelopsia
- Seeing objects move, when in fact they are stationary - kinetic hallucination
- Out-of-Body Experience - people can see their entire selves or parts of themselves duplicated in their migraine aura. These phenomena have been depicted by artists who experienced the symptoms, so have been accurately recorded and illustrated.
Other Transient or Permanent Visual Disturbances Related to Migraine
Apart from migraine aura, other symptoms related to ocular migraine can occur, called Transient Visual Disturbances of Migraine
Persistent retinal images - called palinopsia
This can cause the visual field to fill up with duplicate copies of the object in front of you. It can also cause a tracking phenomenon where a moving object leaves a trace of darkness in its wake - some have called this cinematographic vision
Other Persistent Visual Phenomena
One series of 10 cases from 1995 described people with a history of migraine or with migrainous symptoms that resulted in persisting visual symptoms.
These included seeing dots, bubbles, haziness, heat waves, circles, squares, or squiggles.
These were usually in the whole visual field, and could last for months.
Brain imaging with MRI was normal. The point is that migraine can lead to persistent visual symptoms in a small number of people without any sign of stroke. However, persisting visual symptoms of ocular migraine need to be investigated.
A very small number of people with ocular migraine have underlying structural brain problems found on brain imaging/scans.
The features that suggest that there is an underlying abnormality included:
- Complete absence of headache - pure visual aura without headache should be investigated
- Very brief aura symptoms - aura symptoms that appear like brief flashes of light for seconds only should raise the possibility of a problem
- Onset of first symptoms of ocular migraine aged 40 or over. Older onset pure aura with or without headache can be a risk for a structural problem.
- Highly stereotyped aura, especially without any headache. These aura which never ever vary should probably be scanned.
- Increasing frequency of aura without headache
- A history of epilepsy
Underlying disease causing secondary symptoms of ocular migraine
- No cause - just to remind you that the vast people with symptoms of ocular migraine or migraine visual aura, have ordinary migraine aura!
- Blood disorders - too many platelets (thrombocytosis), too many red blood cells (polycythaemia)
- Vascular malformations of the brain (cavernomas, arterio-venous malformations)
- Occipital lobe stroke - infarction or haemorrhage
- Venous Infarction secondary to Venous Sinus Thrombosis
- Convexity subarachnoid haemorrhage - which causes bleeding on the surface of the brain without causing acute headache, and can be a sign of cerebral amyloidosis.
- Tumours of the occipital lobe, or visual pathways - including benign tumours like meningioma or cancerous groqths - metastatic, astrocytoma, oligodendroglioma
- Cerebral Abscess
- Retinal diseases - Acute Multifocal Posterior Placoid Pigment Epitheliopathy