Visual snow
| Visual snow | |
|---|---|
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| Animated example of visual snow-like noise | |
| Classification and external resources | |
| ICD-10 | Xxx.x |
| ICD-9-CM | xxx |
Visual snow, visual static, or persistent visual snow is a transitory or persisting medical disorder in which sufferers see snow or television-like static in parts or the whole of their visual fields, constantly in all light conditions, even visible in daylight, darkness and with closed eyelids. The severity or density of the "snow" differs from one person to the next; in many circumstances, the condition negatively affects daily life, making it difficult or impossible to read, drive, perform routine tasks, see in detail (even in bright daylight) or focus correctly because of afterimages and numerous other visual and non-visual co-morbidities, as discussed below. Indeed, medical literature refers to the condition as "disabling" and "debilitating." The use of computer screens can exacerbate symptoms considerably in many patients. Also see Closed eye hallucination: Level 1, which makes people aware that they start to notice it even in normal situations, because what-ever is visible in the dark will be visible on any color plain surface.
Little is known about this rare condition, and it has conventionally been regarded as a variant of migraine aura—though recent research shows this is not the case. It is commonly confused with floaters by opticians and doctors alike when patients describe their symptoms, leading to misdiagnosis as well as underdiagnosis of visual snow. At times, if it is visible on certain surfaces it can be because our eyes sees vitreous fluid present inside our eyes (entopic phenomenon). In some cases, it can be vitreous degeneration.
Visual snow is now regarded as a unique syndrome—usually presenting with other symptoms, such as persistent afterimages, photophobia, enhanced blue field entoptic phenomenon and tinnitus.
Recent research has confirmed a brain hypermetabolism in persons with visual snow, located principally in the right lingual gyrus. Before this, no other cause for visual snow had been identified. Insofar as sufferers of visual snow had undergone ophthalmic, neurological and psychiatric examinations, no systematic problems besides the visual snow were found. The recent research that indicates this disorder occurs in the brain has important ramifications for the possibility of potential treatment. However, standard treatment protocols have yet to be established.
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