Experiencing snow or television-like static in parts or whole visual field, is known as visual snow.
When present constantly for longer period of time, is diagnosed as a major symptom of so called persistent migraine aura (headache can be absent).
According to some clinical data, this visual snow can be a side effect of optic neuritis, an inflammation of optic nerve as a part of multiple sclerosis.
See neurologist and ophthalmologist for complete evaluation!