A patient may see "snow" due to disordered visual processing, sometimes in association with migraine.
Features of visual snow syndrome:
(1) large number of tiny flickering dots ("snow") seen across the entire visual field at the same time
(2) may accompanied by photophobia and palinopsia (persistence of a visual image after the stimulus has been removed)
(3) may be episodic or persistent
The snow is distinct from floaters.
Episodic visual snow may be associated with migraine. Because the snow does not show progression across the visual fields it is considered distinct from a migranous aura. Movement of an aura across the visual fields is associated with cortical spread.
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