Visual snow in the context of Visual field


Visual snow in the context of Visual field

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⭐ Core Definition: Visual snow

Visual snow syndrome (VSS) is an uncommon neurological condition in which the primary symptom is persistent flickering white, black, transparent, or colored dots across the whole visual field. It is distinct from the symptom of visual snow itself, which can also be caused by several other causes; these cases are referred to as "VSS mimics."

Other common symptoms are palinopsia, enhanced entoptic phenomena, photophobia, and tension headaches. The condition is typically always present and has no known cure, as viable treatments are still under research. Astigmatism, although not presumed connected to these visual disturbances, is a common comorbidity. Migraines and tinnitus are common comorbidities that are both associated with a more severe presentation of the syndrome.

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Visual snow in the context of Afterimage

An afterimage, or after-image, is an image that continues to appear in the eyes after a period of exposure to the original image. An afterimage may be a normal phenomenon (physiological afterimage) or may be pathological (palinopsia). Illusory palinopsia may be a pathological exaggeration of physiological afterimages. Afterimages occur because photochemical activity in the retina continues even when the eyes are no longer experiencing the original stimulus.

The remainder of this article refers to physiological afterimages. A common physiological afterimage is the dim area that seems to float before one's eyes after briefly looking into a light source, such as a camera flash. Palinopsia is a common symptom of visual snow.

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Visual snow in the context of Hallucinogen persisting perception disorder

Hallucinogen persisting perception disorder (HPPD) is a non-psychotic disorder in which a person experiences lasting or persistent visual hallucinations or perceptual distortions after using drugs. This includes after psychedelics, dissociatives, entactogens, tetrahydrocannabinol (THC), and SSRIs. Despite being a hallucinogen-specific disorder, the specific contributory role of psychedelic drugs is unknown.

Symptoms may include visual snow, trails and after images (palinopsia), light fractals on flat surfaces, intensified colors, altered motion perception, pareidolia, micropsia, and macropsia. Floaters and visual snow may occur in other conditions.

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Visual snow in the context of Floater

Floaters or eye floaters are sometimes-visible deposits (e.g., the shadows of tiny structures of protein or other cell debris projected onto the retina) within the eye's vitreous humour ("the vitreous"), which is normally transparent, or between the vitreous and retina.They can become particularly noticeable when looking at a blank surface or an open monochromatic space, such as a blue sky.Each floater can be measured by its size, shape, consistency, refractive index, and motility. They are also called muscae volitantes (Latin for 'flying flies'), or mouches volantes (from the same phrase in French). The vitreous usually starts out transparent, but imperfections may gradually develop as one ages. The common type of floater, present in most people's eyes, is due to these degenerative changes of the vitreous. The perception of floaters, which may be annoying or problematic to some people, is known as myodesopsia, or, less commonly, as myodaeopsia, myiodeopsia, or myiodesopsia. It is not often treated, except in severe cases, where vitrectomy (surgery) and laser vitreolysis may be effective.

Floaters are visible either because of the shadows that imperfections cast on the retina, or because of the refraction of light that passes through them, and can appear alone or together with several others as a clump in one's visual field. They may appear as spots, threads, or fragments of "cobwebs", which float slowly before the observer's eyes, and move especially in the direction the eyes move. As these objects exist within the eye itself, they are not optical illusions but are entoptic phenomena (caused by the eye itself). They are not to be confused with visual snow, which is similar to the static on a television screen, although these two conditions may coexist as part of a number of visual disturbances which include starbursts, trails, and afterimages.

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