“Visual snow” is a visual phenomenon whereby individuals see what appears to be snow or static, as one would experience with poor television reception. It can be transitory or persistent, involving either a part or the totality of the visual field, and usually more noticeable against darker backgrounds. Some patients liken it to camera noise in low-light conditions. Its severity is variable, but it has been known to have an extremely negative impact on daily life, rendering focusing and reading difficult.

Often, no definitive etiology for visual snow is discovered, despite efforts on the parts of those in the , neurologic and ophthalmologic fields—and this, coupled with the decrease in quality of life associated with visual snow sufferers, has led to secondary , , and . It is commonly considered to be associated with migraine (as an unusual form of aura), or hallucinogen intake. Unfortunately, the association of visual snow with illicit drug use can add insult to injury when a patient is falsely presumed to be a past or present substance abuser.

One can easily imagine this scenario occurring with patients on chronic pain , even if their pain is due to migraine.

(HPPD) is the term given the onset of visual snow following the use of hallucinogenic psychedelic drugs. Interestingly, visual snow in HPPD is more commonly referred to as “aeropsia” (from the Greek for “seeing air”). There can be considerable latency between the last (and occasionally, the only) intake of drug and the onset of HPPD. Hence, up until now, it has been dogma that a thorough and chronologically complete drug history be taken when health care providers embark on the diagnostic work-up of visual snow.

I write “up until now” because recent research presented at the American Academy of Neurology’s annual meeting has concluded that visual snow is not likely the product of illicit drug use.

The research was undertaken by Dr. Christoph Schankin at the University of California, San Francisco, because visual snow studies have heretofore involved small numbers of patients, and advocacy groups want more definitive answers. Dr. Schankin’s study involved 120 individuals reporting similar visual symptoms.

Because there was so much variation in the visual complaints between subjects, the researchers concentrated on the approximately 60 subjects who were experiencing solid, stationary black and white dots as part of their daily visual lives. Study participants additionally reported darting white objects when viewing the sky, colored waves with eyes shut, less than ideal night vision, and trails tailing along after moving objects.

It was found that, while migraine headaches are indeed common in patients with visual snow, visual snow also affects a significant number of individuals without a history of migraine or hallucinogenic drug use.

More than one-half of the subjects reported having experienced migraine headaches, but Dr. Schankin emphasized that the headaches were not related to the visual phenomena. He concluded that visual snow is in itself a disease entity, clinically distinct from migraine with aura.

There is still much to learn about visual snow, particularly its etiology from the standpoints of anatomy and physiology, and the ideal treatment, which currently involves trial and error dosing with a variety of anti-seizure medications. Still, this recent research can give some hope to those coping with this condition—and some ammunition when the medical establishment assumes its all due to past or current illegal drug use.