LOS ANGELES—“Visual snow” is part of a unique clinical syndrome that is distinct from visual aura in migraine, according to Christoph Schankin, MD, a fellow in the Department of Neurology, University of California, San Francisco, Headache Center. Dr. Schankin discussed visual snow syndrome at the 54th Annual Scientific Meeting of the American Headache Society (AHS). Also known as positive persistent visual disturbance, visual snow is characterized by tiny, usually black and white, dots in the entire visual field that are always present. Patients usually describe these dots as dynamic, meaning that they change their color rapidly and often. Other visual symptoms often linked with this phenomenon include prolonged afterimages, trailing, photophobia, floaters, bright flashes, color swirls, and impaired night vision.
The literature includes scant evidence of this syndrome. A few case series exist, and often patients are diagnosed with persistent migraine aura or a perceptual disorder resulting from hallucinogen use. Most patients who deny intake of illicit drugs have a history of migraine. But is this visual phenomenon migraine aura? Dr. Schankin and colleagues sought to investigate and further characterize this syndrome.
The investigators used survey results provided by the Eye on Vision Foundation (www.eyeonvision.org), a charitable organization devoted to the study of visual snow, floaters, and macular degeneration and support of those afflicted with these conditions. In addition to reported “visual snow,” trailing and prolonged afterimages (palinopsia) were present in 48% and 63% of the surveyed patients, respectively. Entopic phenomena such as floaters and photopsia in the form of bright flashes were reported by 44% and 73% of the patients, respectively. Little objects moving on the blue sky were noted by 57% of the patients, and 41% of patients saw colored swirls when they closed their eyes. Most of the patients described sensitivity to light and impaired night vision.