Visual snow is the visual condition of seeing static (which is defined as white or black dots in parts of, or the whole of a patient's visual field. The problem is typically persistent and can last extended periods of time (even years.)
There have been medications developed which act as effective treatments for visual snow. They include Lamotrigine, Acetazolamide, or Verapamil. These do not always yield relief of symptoms, however.
Neuro-ophthalmologists will assert that visual snow is not a medical condition in and of itself, but rather, that it is a poorly understood symptom of other underlying neurological conditions - the presentations of which are usually under-reported due to less noticeable symptoms until the time that visual snow is recognized.
Usually what happens, is that people report seeing this "snow" which is not unlike the visual noise which is possible on a television screen - and it is hypothesized that this visual snow is the result of a patient's own intrinsic visual noises. Some people find it more noticeable in darker settings. To quote Dunn Rieke, (August 2006). "The impact of photoreceptor noise on retinal gain controls" -
"Current Opinion in Neurobiology "The intrinsic dark noise of primate cones is equivalent to ~4000 absorbed photons per second at mean light levels, below this the cone signals are dominated by intrinsic noise"
Patients affected by this phenomena, In addition to visual snow, often experience other types of visual disturbance such as starbursts, increased amount of afterimages, (even in heavier light conditions) as well as visual floaters, visual trails, and many other disturbances which vary dependant on the underlying cause of the condition.
Again, exact causes are unclear because they come from a wide array of possible underlying conditions. Identifying the underlying condition can be made easier by identifying additional symptoms with comorbidities; such as migraines, and migraines with aura, tinnitus, and so on. Once comorbidities have been identified, narrowing down a diagnosis can be made easier.
Persistent visual snow can be featured as a leading additional symptom to other disorders, such as migraines, in which case, visual snow is a complication called "persistent aura without infarction." More commonly this condition is referred to as Persistent Migraine Aura (or PMA). In clinical sub-forms of migraine headaches, visual snow may be absent, and the Migraine Aura may not take typical forms with regards to visual snow, but instead manifests with a large variety of neurologically focal symptoms.
It is worth noting that the role of hallucinogens in visual snow is not well understood. Hallucinogen persisting perception disorder (HPPD), a condition caused by hallucinogenic drug use, and it's sometimes linked to visual snow. Both the connection of visual snow to HPPD and the cause and prevalence of HPPD is disputed. Most of the evidence for both is generally anecdotal and is subject to spotlight fallacy.
Proposed diagnostic criteria for the "visual snow" syndrome are as follows:
There is no real established treatment for visual snow which has proven to be incredibly effective. It's difficult to resolve visual snow, even with treatment - but on the upside, in most cases, it tends to dissipate over time and it's possible to reduce symptoms and improve quality of life through treatment which involves the drugs mentioned at the beginning of the article.