Visual snow
From Free net encyclopedia
Visual snow is a little-known condition in which people see snow or television-static in their field of vision. Usually the condition worsens in low light conditions or when closing one eye. It is quite similar to the aeropsia seen by HPPD patients, suggesting an identical underlying cause. However, people who see visual snow do not necessarily have a history of drug use. Instead, the onset has been associated with diverse events, such as stress, LSD/MDMA use, anti-depressant usage, dehydration, or panic attacks. Some other patients fail to find such an event in their lives, instead saying the snow came out of nowhere or has been with them for their whole life. However it is also believed that more logical causes such as prolonged use of a VDU or other bright light sources can cause similar symptons, which some believe may be indicating overuse, damage or a weakness of the optic nerve.
People with visual snow often have floaters and some have other visual disturbances as well, like starburst, increased afterimages and trails. This, and the fact that no physical anomalies are ever found with people complaining of VS, might imply that instead of an illness, visual snow is an entoptic phenomenon that is noticed mainly by those who are very conscious of their vision. In this respect, it might be comparable to Haidinger's brush.
Because there is little scientific data on the condition, visual snow is rarely diagnosed as such. If the complaints lead to a diagnosis at all, it is often seen as a persistent form of acephalalgic migraine.
There currently is no established treatment for visual snow, although some people claim to have benefited from the anti-seizure medicine clonazepam or from the corticosteroid prednisone. However, with very little scientific research on the condition taking place, such treatments remain based solely on anecdotal evidence.
Visual snow is also known as 'visual noise'. The name visual snow is generally preferred due to the common use of 'visual noise' when describing a similar but different sympton in closed-eye hallucinations. 'Visual noise' is also a technical term used to describe unwanted data captured from electronic Imaging and traditional photography.