Patients with VS suffer a pan-field, dynamic visual disturbance described as continuous TV-static-like tiny flickering dots. The current diagnostic criteria require at least two additional visual symptoms from: palinopsia (afterimages and trailing), entoptic phenomena (floaters, blue field entoptic phenomenon, photopsia, self-light of the eye), photophobia and nyctalopia.

We performed a web-based survey on patients with self-assessed visual snow (n=1104,either with the complete visual snow syndrome (n=1061) or with visual snow without the syndrome (n=43). We also describe a population of patients (n=70) with possible hallucinogen persisting perception disorder who presented clinically with visual snow syndrome.

The visual snow population had an average age of 29 years and no gender prevalence. The disorder usually started in early life and around 40% of patients had symptoms for as long as they could remember. The most commonly experienced static was black and white. Floaters, afterimages and photophobia were the most reported additional visual symptoms. A latent class analysis showed that visual snow does not present with specific clinical endophenotypes. Severity can be classified by the amount of visual symptoms experienced. Migraine and tinnitus had a very high prevalence and were independently associated with a more severe presentation of the syndrome.

Our data confirm earlier work on this under-recognized disorder. Clinical characteristics of visual snow did not differ from the previous cohort in the literature, supporting validity of the current criteria. Visual snow likely represents a clinical continuum, with different degrees of severity. On the severe end of the spectrum it is more likely to present with its common comorbidities, migraine and tinnitus. Visual snow does not depend on the effect of psychotropic substances on the brain.