- Visual snow
Visual snow is a transitory or persisting visual symptom where people see snow or television-like static in parts or the whole of their visual fields, especially against dark backgrounds. It is much like camera noise in low light conditions.
The severity or density of the "snow" differs from one person to the next; in some circumstances, it can inhibit a person's daily life, making it difficult to read, see in detail and focus correctly. The "snow" is more generalized than the "blue-sky sprites" seen in the blue field entoptic phenomenon.
No etiology for visual snow has been identified, and anecdotal reports point to a multitude of associated conditions, possibly rendering it a non-specific symptom. Insofar as sufferers of visual snow have undergone ophthalmic, neurological and psychiatric examinations, no systematic problems besides the visual snow have been identified. Pending recognition of the condition, little medical research is taking place to possibly identify more subtle deviations.
Visual snow can occur in a variety of ophthalmic disorders that can be diagnosed by the presence of additional clinical signs and symptoms. Persisting visual snow can feature as a leading symptom of a migraine complication called persistent aura without infarction, commonly referred to as persistent migraine aura (PMA). It is important to keep in mind that there exist many clinical sub-forms of migraine where headache may be absent and where the migraine aura may not take the typical form of the zigzagged fortification spectrum, but manifests with a large variety of focal neurological symptoms.
A condition that sometimes produces visual snow is optic neuritis (inflammation of the optic nerve), caused by multiple sclerosis (MS). Moreover, a variety of illnesses (e.g. Lyme disease, auto-immune disease) or noxious events (e.g. prolonged use of a VDU, dehydration, over-acidification) have been blamed by sufferers in self-help internet forums as causes of persisting visual snow, but none of these claims have been confirmed by scientific study. Some patients fail to find any apparent causative illness or event in their lives, instead saying the snow came out of nowhere or has been with them for their whole life.
Hallucinogen persisting perception disorder (HPPD) is another condition which has resulted in the onset of the visual snow following the use of hallucinogenic psychedelic drugs. In HPPD, the symptom of the visual disturbances has been described as as aeropsia (literally "seeing the air"). HPPD very rarely occurs after just a single dose of a hallucinogenic drug and with a considerable latency between last drug intake and onset of persistent perception disorder, so taking a thorough life-time drug history is mandatory in the diagnostic work-up of visual snow. In many cases, the neurological action for HPPD is not known, and the majority of evidence surrounding it is anecdotal and difficult to isolate.
Another suggestion is that visual snow is in fact always there, and it is not until adrenaline levels are raised that people begin to notice it. People who suffer from Anxiety disorders such as GAD (generalised anxiety disorder) often mistake "symptoms" such as visual snow and other natural/normal physiological phenomenons (blue field entoptic phenomenon, floaters, halos, light trails) to be life threatening, when in actual fact they have just not noticed them before.
Non-visual symptoms such as tinnitus, depersonalization-derealization, fatigue, speech difficulties and cognitive dysfunction (brain fog) are frequently encountered. Secondary psychiatric sequelae such as anxiety, panic attacks or depression may develop and necessitate appropriate treatment.
There currently is no established treatment for visual snow. In HPPD, clonazepam has been recommended as medication of first choice in patients seeking medical help. Furthermore, drug abstinence is sometimes said to be of major therapeutic importance in HPPD. In persistent aura without infarction, the evidence so far suggests that acetazolamide may be the premier drug for patients with the repetitive form of aura status and that valproate, lamotrigine, or topiramate should be first choices for patients with the continuous form. When these oral drugs are ineffective, an intravenous injection or injections of furosemide should be tried.
However, with very little scientific research on the condition taking place, for the time being the effectiveness of such treatments remains based solely on anecdotal evidence. Beyond pharmacological approaches, appropriate counselling and cognitive behavioral interventions that focus on coping with the condition may be of huge importance.
- ^ International Headache Society. The International Classification of Headache Disorders, 2nd edition. Cephalalgia 2004; 24 (suppl. 1): 1-160.
- ^ Abraham HD. Visual phenomenology of the LSD flashback. Arch Gen Psychiatry 1983; 40: 884-889.
- ^ Podoll K, Dahlem M, Greene S. Persistent migraine aura symptoms aka visual snow.
- ^ Lerner AG, Kladman I, Kodesh A, Sigal M, Shufman E. LSD-induced Hallucinogen Persisting Perception Disorder treated with clonazepam: two case reports. Isr J Psychiatry Relat Sci 2001; 38: 133-136.
- ^ Haan J, Sluis P, Sluis LH, Ferrari MD. Acetazolamide treatment for migraine aura status. Neurology 2000; 55: 1588-1589.
- ^ Rothrock JF. Successful treatment of persistent migraine aura with divalproex sodium. Neurology 1997; 48: 261-262.
- ^ Chen WT, Fuh JL, Lu SR, Wang SJ. Persistent migrainous visual phenomena might be responsive to lamotrigine. Headache 2001; 41: 823-825.
- ^ Podoll K, Dahlem M, Haas DC. Persistent migraine aura without infarction - a detailed description
- ^ Rozen TD. Treatment of a prolonged migrainous aura with intravenous furosemide. Neurology 2000; 55: 732-733.
- Internet Resources For Visual Snow Patients
- Treatment for Visual Snow
- Persistent aura without infarction
- Eye on Vision Foundation Raises Money for Visual Snow Research
- YouTube video showing how many people see with Visual Snow
- Simulation of Visual Snow
Phenomena of the visual system Entoptic phenomena Other phenomena
Wikimedia Foundation. 2010.
Look at other dictionaries:
visual snow — Also known as aeropsia. Both terms refer to a * simple visual hallucination depicting televisionlike static. Visual snow may be either transient or permanent, and it may affect either the whole visual field, or one or more parts of it. In… … Dictionary of Hallucinations
visual snow — noun A condition in which a person sees television like static or noise in their field of vision, especially when against a dark background … Wiktionary
Visual system — The visual system includes the eyes, the connecting pathways through to the visual cortex and other parts of the brain. The illustration shows the mammalian system. The visual system is the part of the central nervous system which enables… … Wikipedia
visual aura — Formerly known as suffusio. The term visual aura is indebted to the Greek noun aura, which means wind, breeze, or smell. It is used to denote an *aura experienced in the visual modality. The earliest known written account of a visual aura… … Dictionary of Hallucinations
Snow Crash — Cover of the U.S. paperback version … Wikipedia
Visual anthropology — is a subfield of cultural anthropology that developed out of the study and production of ethnographic photography, film and since the mid 1990s, new media. While the term is sometimes used interchangeably with ethnographic film , visual… … Wikipedia
Snow (disambiguation) — Snow is a form of precipitation, a crystalline form of ice.Snow may also refer to: * SNOW, a stream cipher * Snow (codec), a video codec * Snow (dessert), the name given to various desserts using whipped egg whites * Snow (ship), a type of two… … Wikipedia
snow lights — Also known as cocaine spots. The term snow lights is indebted to the noun snow, which is slang for cocaine. Originally a street term, the expression snow lights was brought to the attention of the scientific community in 1978 by the American… … Dictionary of Hallucinations
Snow White — This article is about the traditional fairy tale. For the Disney character, see Snow White (Disney). For other uses, see Snow White (disambiguation). Snow White Snow White in her coffin, Theodor Hosemann, 1852 Folk tale … Wikipedia
Snow Mountain (Colusa County, California) — Infobox Mountain Name=Snow Mountain (East) Photo=Img3081.jpg Caption=Snow Mountain (left massif) from Interstate 5. The peak to the right (north) is Saint John Mountain. Elevation=Convert|7056|ft|m|0 Location= Colusa / Lake Counties, California,… … Wikipedia