Visual snow

How it works

The snow is constant. The dots are tiny, flickering, black and white or coloured, and they cover everything you look at. They are there with eyes open and closed, in light and in the dark¹. Many people with visual snow also have palinopsia, afterimages that linger too long¹². Many also see stronger floaters and blue-field dots than usual, are sensitive to light, hear tinnitus, and get migraines¹.

Eye tests come back normal. The problem is in how the brain processes vision. Researchers think that neurons in the visual areas of the brain fire too easily. This is called hyperexcitability¹. The exact cause is not known. Visual snow is not a hallucination. The brain is not inventing objects. One idea is that the brain fails to filter out visual signals it would normally ignore¹. Visual snow can start at any age, but it often starts at birth, in the late teens, or in early adulthood¹.

How common it is

The best-known figure, about 2%, comes from one online survey of 1,015 UK adults. They were not told the survey was about visual snow⁴. A study of 750 Italian university students found under 1%, and none of those with it had a diagnosis⁵. Because it often starts early in life, age at onset is hard to separate from age at diagnosis in the data available.

Is it a problem?

It is not dangerous. Visual snow is not known to damage the eyes or the brain, and it does not lead to blindness¹. For many people it is mild. Doctors mainly offer reassurance that it is harmless⁶. Online groups let people talk with others who have it³. Tinted lenses are sometimes tried, but there is little evidence that they work⁶. Medicines have been tried with mixed results, and there is no reliable treatment yet¹.

See an eye doctor if you notice it for the first time, and a neurologist if the eyes are normal. Go sooner if it starts suddenly, or comes with a headache, weakness, or a new medicine. That rules out other causes. Once diagnosed, visual snow does not need emergency care.