Visual snow is a transitory or persisting visual symptom where people see snow or television-like static in parts or the whole of their visual fields, especially against dark backgrounds. It is much like camera noise in low light conditions.
The severity or density of the "snow" differs from one person to the next; in some circumstances, it can inhibit a person's daily life, making it difficult to read, see in detail and focus correctly. The "snow" is more generalized than the "blue-sky sprites" or "worms" seen in the blue field entoptic phenomenon.
No etiology for visual snow has been identified, and anecdotal reports point to a multitude of associated conditions, possibly rendering it a non-specific symptom. Insofar as sufferers of visual snow have undergone ophthalmic, neurological and psychiatric examinations, no systematic problems besides the visual snow have been identified. Pending recognition of the condition, little medical research is taking place to possibly identify more subtle deviations.
Read more about Visual Snow: Causes, Related Symptoms, Treatments
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