Visual snow
Encyclopedia
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 field
s, 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.
, floater
s, trails, and many others.
Non-visual symptoms such as tinnitus
, depersonalization
-derealization
, fatigue, speech difficulties and cognitive dysfunction
(brain fog) are frequently encountered. Secondary psychiatric sequela
e such as anxiety, panic attacks or depression may develop and necessitate appropriate treatment.
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.
Noise (video)
Noise, in analog video and television, is a random dot pattern of static displayed when no transmission signal is obtained by the antenna receiver of television set and other display devices...
or television-like static
Noise (video)
Noise, in analog video and television, is a random dot pattern of static displayed when no transmission signal is obtained by the antenna receiver of television set and other display devices...
in parts or the whole of their visual field
Visual field
The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments", while 'field of view' "refers to the physical...
s, 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
Blue field entoptic phenomenon
The blue field entoptic phenomenon or Scheerer's phenomenon is the appearance of tiny bright dots moving quickly along squiggly lines in the visual field, especially when looking into bright blue light...
.
No etiology
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
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
Ophthalmology
Ophthalmology is the branch of medicine that deals with the anatomy, physiology and diseases of the eye. An ophthalmologist is a specialist in medical and surgical eye problems...
, neurological
Neurology
Neurology is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue,...
and psychiatric
Psychiatry
Psychiatry is the medical specialty devoted to the study and treatment of mental disorders. These mental disorders include various affective, behavioural, cognitive and perceptual abnormalities...
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.
Causes
Migraine
Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
complication called persistent aura without infarction
Persistent aura without infarction
Persistent migraine aura without infarction is a little-known condition first described under the designation prolonged migraine aura status that is not yet fully understood. PAWOI is said to be a possible cause of a variety of neurological symptoms, including visual snow, loss of vision,...
, 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
Optic neuritis
Optic neuritis is the inflammation of the optic nerve that may cause a complete or partial loss of vision.-Causes:The optic nerve comprises axons that emerge from the retina of the eye and carry visual information to the primary visual nuclei, most of which is relayed to the occipital cortex of the...
(inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
of the optic nerve
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
), caused by multiple sclerosis
Multiple sclerosis
Multiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...
(MS). Moreover, a variety of illnesses (e.g. Lyme disease
Lyme disease
Lyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...
, auto-immune disease) or noxious events (e.g. prolonged use of a VDU, dehydration
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
, 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
Hallucinogen persisting perception disorder
Hallucinogen persisting perception disorder is a disorder characterized by a continual presence of visual disturbances that are reminiscent of those generated by the ingestion of hallucinogenic substances. Previous use of hallucinogens by the person is needed, though not sufficient, for...
(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.
Related symptoms
In addition to visual snow, many sufferers have other types of visual disturbances such as starbursts, increased afterimagesPalinopsia
Palinopsia is a visual disturbance that causes images to persist to some extent even after their corresponding stimulus has left. These images are known as afterimages and occur in persons with normal vision...
, floater
Floater
Floaters are deposits of various size, shape, consistency, refractive index, and motility within the eye's vitreous humour, which is normally transparent. At young age the vitreous is perfectly transparent, but during life imperfections gradually develop. The common type of floater, which is...
s, trails, and many others.
Non-visual symptoms such as tinnitus
Tinnitus
Tinnitus |ringing]]") is the perception of sound within the human ear in the absence of corresponding external sound.Tinnitus is not a disease, but a symptom that can result from a wide range of underlying causes: abnormally loud sounds in the ear canal for even the briefest period , ear...
, depersonalization
Depersonalization
Depersonalization is an anomaly of the mechanism by which an individual has self-awareness. It is a feeling of watching oneself act, while having no control over a situation. Sufferers feel they have changed, and the world has become less real, vague, dreamlike, or lacking in significance...
-derealization
Derealization
Derealization is an alteration in the perception or experience of the external world so that it seems unreal. Other symptoms include feeling as though one's environment is lacking in spontaneity, emotional coloring and depth. It is a dissociative symptom of many conditions, such as psychiatric and...
, fatigue, speech difficulties and cognitive dysfunction
Cognitive dysfunction
Cognitive dysfunction is defined as unusually poor mental function, associated with confusion, forgetfulness and difficulty concentrating...
(brain fog) are frequently encountered. Secondary psychiatric sequela
Sequela
A sequela) is a pathological condition resulting from a disease, injury, or other trauma.Chronic kidney disease, for example, is sometimes a sequela of diabetes, and neck pain is a common sequela of whiplash or other trauma to the cervical vertebrae. Post-traumatic stress disorder may be a...
e such as anxiety, panic attacks or depression may develop and necessitate appropriate treatment.
Treatments
There currently is no established treatment for visual snow. In HPPD, clonazepamClonazepam
Clonazepamis a benzodiazepine drug having anxiolytic, anticonvulsant, muscle relaxant, and hypnotic properties. It is marketed by Roche under the trade name Klonopin in the United States and Rivotril in Australia, Brazil, Canada and Europe...
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
Acetazolamide
Acetazolamide, sold under the trade name Diamox, is a carbonic anhydrase inhibitor that is used to treat glaucoma, epileptic seizures, Idiopathic intracranial hypertension , altitude sickness, cystinuria, and dural ectasia...
may be the premier drug for patients with the repetitive form of aura status and that valproate, lamotrigine
Lamotrigine
Lamotrigine, marketed in the US and most of Europe as Lamictal by GlaxoSmithKline, is an anticonvulsant drug used in the treatment of epilepsy and bipolar disorder. It is also used as an adjunct in treating depression, though this is considered off-label usage...
, or topiramate
Topiramate
Topiramate is an anticonvulsant drug. It was originally produced by Ortho-McNeil Neurologics and Noramco, Inc., both divisions of the Johnson & Johnson Corporation. This medication was discovered in 1979 by Bruce E. Maryanoff and Joseph F. Gardocki during their research work at McNeil...
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.
See also
- AsthenopiaAsthenopiaAsthenopia or eye strain is an ophthalmological condition that manifests itself through nonspecific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache and occasional double vision...
- Closed-eye hallucinationClosed-eye hallucinationClosed-eye hallucinations and closed-eye visualizations are a distinct class of hallucination. These types of hallucinations generally only occur when one's eyes are closed or when one is in a darkened room. They are a form of phosphene....
- Dark retreatDark retreatDark retreat refers to advanced practices in the Dzogchen lineages of the Nyingmapa, Bönpo and other schools of Tibetan Buddhism.The time period dedicated to dark retreat varies from a few hours to decades. Dark Retreat in the Himalayan tradition is a restricted practice only to be engaged by the...
- Ectopia lentisEctopia lentisEctopia lentis is a displacement or malposition of the eye's crystalline lens from its normal location. A partial dislocation of a lens is termed lens subluxation or subluxated lens; a complete dislocation of a lens is termed lens luxation or luxated lens.-Ectopia lentis in dogs and cats:Although...
- EigengrauEigengrauEigengrau , also called Eigenlicht , dark light, or brain gray, is the color seen by the eye in perfect darkness...
- Floatation tank
- Hallucinations
- Human eyeHuman eyeThe human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
- MigraineMigraineMigraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
- PhosphenePhospheneA phosphene is a phenomenon characterized by the experience of seeing light without light actually entering the eye. The word phosphene comes from the Greek words phos and phainein...
- Prisoner's cinemaPrisoner's cinemaThe Prisoner's Cinema is a phenomenon reported by prisoners confined to dark cells and by others kept in darkness, voluntarily or not, for long periods of time. It has also been reported by truck drivers, pilots, and practitioners of intense meditation...
- Shot noiseShot noiseShot noise is a type of electronic noise that may be dominant when the finite number of particles that carry energy is sufficiently small so that uncertainties due to the Poisson distribution, which describes the occurrence of independent random events, are of significance...
- VisionVisual perceptionVisual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...