The Origins Of Visual Snow

The Origins Of Visual Snow

Here is the video and a short summary of James T. Fulton’s presentation at the 2018 Visual Snow Conference event. He discusses where Visual Snow and associated symptoms may originate from within the visual system and why. He also discusses the data from surveys on his website.

Visual Snow Conference

In total there are five presentations from the Visual Snow Conference that I have chosen to write about. I recommend that you read about them/watch the videos in this order. The first two are more general, the last three go into more complex detail. If you have already seen some of the videos I recommend that you watch them again anyway, as it is easy to miss certain details.

1. Four Myths About Visual Snow (Peter Goadsby)

2. Visual Snow And Sensory Misperception (Owen White)

3. Behavioural Research Into Visual Snow (Joanne Fielding)

4. The Origins Of Visual Snow (James T. Fulton)

5. Visual Snow And Visual Pathways (Viktoria Pelak)

* These are not necessarily the presentation titles the authors used at the event

Four Quadrants And The Visual Cortex

Optic Chiasm Visual Pathway

Fulton in the presentation shows a diagram that divides the brain circuit according to different stages of vision. That diagram shows both information going towards the brain and outwards from the brain to muscles and glands. Our focus he says is on the incoming information that is processed and sent to cognitive parts of the brain. 

From the retina information is split up into three different paths.Two of them (shown in diagram above) split into two as information is sent to thalamus and then onto the primary visual cortex.

This split of information effectively forms four quadrant sections of an eventual image.

Thalamus And The Origins Of Visual Snow

A third path however goes separately from the primary visual cortex to the thalamus. Fulton brings attention to a piece of thalamus which is he says can’t be found in textbooks. The perigeniculate nucleus (PGN)/pulvinar couple he says is a high resolution visual area in the centre of the brain, and this is where the third path goes to.

Throughout the early stages and with the involvement of the primary visual cortex a uniform image has not yet been fully formed. In addition to the four quadrants this thalamus area adds a central section to the eventual image.

He says that if you see uniform static or “noise” the origin has to be at one of the later stages when these sections are put together. With his knowledge he says that he suspects parts of the thalamus, or associative area (saliency map) – where Fulton says the brain puts together its version of what you see and says to cognitive parts of the brain what it actually looks like.

Four quadrants and a central section come together in later stages

Visual Snow And Visual Snow Syndrome

Fulton underlines that some people have Visual Snow and others have symptoms in a syndrome

Here it is important to remember what Peter Goadsby said about the clinical classification being for research purposes. Generally, but not always will people have additional associated symptoms is the implication from Fulton. Do those without additional symptoms still have “Visual Snow” – yes, do they match the current proposed clinical classification for “Visual Snow Syndrome” – no.

Something which for example is common but not part of the classification, is that around 80% of people with Visual Snow reportedly have tinnitus – suggesting that both could have the same underlying physical origin, as Fulton says.

Entoptic phenomenon such as blue sky phenomenon, and floaters can be part of the syndrome but they are not “Visual Snow”. Entoptic phenomenon literally are those that occur in the eye at the very early stages, while as we hear Visual Snow occurs in the later stages of the Visual System. So their physical origins are entirely separate from this point of view.
 
Floaters he points out can come in three forms, which he shows on the slides. Solid black dots can be from a blood leak near the retina, squiggly dots are normal white blood cells, while transparent shapes are actually dust on the cornea. Visual Snow also comes in different forms: some people see Visual Snow as machine gun bullets he says, some see TV type noise (analog televisions). There is a degree of variation (illustrated below) and this may relate to slightly different physical origins within the visual system.

Three example variations in Visual Snow appearance: pink noise, white noise, popcorn noise (left-right)
Three types of Visual Snow according to Fulton's surveys

Survey

Fulton discusses the results of a survey he had on his website with about 150 respondents:

  • 3% of had Visual snow from birth. He says there is no known way to evaluate if young children have the condition but the mother usually recognises something is wrong at 4/5 years old.
  • 30% attribute recreational drugs as a cause, frequently it appears with drugs two-three weeks after.
  • 10% find the condition seriously debilitating and for example pull out of education.
  • He also found according to his survey that Visual Snow is generally not progressive and coloured static is uncommon. Most cases are described with black and white static, although it is more likely to be translucent he says.

The Video

Play Video

My Thoughts

My thoughts are mostly covered here where I gave a preliminary discussion about Mr Fulton’s presentation. There is more detail that can be found on Mr Fulton’s website and in that earlier post.

From a practical perspective I think it is important to underline the point that Visual Snow as a syndrome can be different for different people – the dominant symptom is however always persistent pan-field visual static. It is also important to appreciate the distinction between the symptom of Visual Snow and other symptoms in a syndrome.

It is worth as well to explicitly state having Visual Snow has nothing to do with optic neuritis, retinal detachment and other horror misconceptions that can be found in online discussions.

The information that those with Visual Snow possess needs to be interpreted by experts such as Mr Fulton to add to theoretical understanding, so please take the time to fill out his survey.

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