This post lists some of the symptoms sometimes associated with Visual Snow and seen in Visual Snow Syndrome. It may provide a useful reference for those who are unsure about symptom terminology.
This post contains simplified information and is based on my current understanding. For more information and to form a more detailed understanding of your own: please read the original research papers, watch the presentations from the Visual Snow Conference along with the supplementary videos from the Visual Snow Initiative, and read the information on James T. Fulton’s website.
Warning: this article contains images that those sensitive to flashing images and pattern glare may find unpleasant.
What is Visual Snow? Do I have Visual Snow?
Visual Snow is the symptom where one sees dynamic dots across the whole field of vision persistently. These dots are also generally described as being tiny and flickering.
To say you «have Visual Snow» is to mean that you have this symptom and these dots do not go away (although they may at times become less noticeable).
Anything else described as Visual Snow may not be «Visual Snow», or is actually a reference to «Visual Snow Syndrome». Unlike for Visual Snow Syndrome, the origin of this symptom of Visual Snow is not necessarily important for its definition.
In a 2017 survey of 514 patients with Visual Snow it was found their Visual Snow had different characteristics. These were: black and white (n=287), coloured (n=222), flashing (n=227) and transparent (n=272). Visual Snow may also differ in size, density, and speed (if flashing).
According to James T. Fulton’s surveys there are three broad types of static possibly seen as visual snow – Popcorn noise (“pulse type visual snow”), White noise, and Pink noise (“broadband type visual snow”). These have different frequencies and may originate at different stages of vision, therefore they also have distinct visible characteristics. As he describes them: popcorn noise presents scattered dots, white noise a TV like blotchy field of vision, and pink noise a fuzziness across vision.
Visual Snow can vary in appearance, but other symptoms are not Visual Snow. See further below under «Visual Snow and Associated Symptoms» for a clarification of symptoms sometimes seen together with Visual Snow and/or mistaken for Visual Snow.
If you do not have the symptom of Visual Snow, then very simply: you do not have Visual Snow or Visual Snow Syndrome.
What is Visual Snow Syndrome?
Visual Snow Syndrome is a clinical term for when Visual Snow comes together with a group of specific symptoms that are not better explained by another disorder.
The classification for Visual Snow Syndrome purposefully excludes certain symptoms and groups for the purposes of clinical research. Due to this it may also exclude people who have Visual Snow as per the definition above, but simply do not fit the current criteria. Visual Snow Syndrome is not the same thing as Visual Snow.
A shortened version of the proposed clinical classification for Visual Snow Syndrome:
A) Visual snow: dynamic, continuous, tiny dots in the entire visual field lasting longer than 3 months.
B) Presence of at least two additional visual symptoms of the four following categories:
(i) Palinopsia. (ii) Enhanced entoptic phenomena. (iii) Photophobia (iv) Nyctalopia
C) Symptoms are not consistent with typical migraine visual aura
D) Symptoms are not better explained by another disorder. I.e. Normal ophthalmology tests; not caused by previous intake of psychotropic drug
Source: Puledda, F., Schankin, C., Digre, K., & Goadsby, P. J. 2017. Visual snow syndrome: what we know so far.
The unavoidable problem with this classification is that it is based on an as yet incomplete understanding. «Visual Snow Syndrome» should therefore be seen as vocabulary for use by researchers and in a clinical setting, rather than for those with Visual Snow on a day-to-day basis. Unfortunately there is no ideal alternative word for Visual Snow when it comes with other associable symptoms.
Visual Snow Syndrome:
Entoptic Phenomena literally translates as «phenomena inside the eye». A heightened awareness of Entoptic Phenomena is part of the clinical classification of Visual Snow Syndrome.
Entoptic Phenomena are seen within the wider population, particularly those who are older when their eyes physically deteriorate.
Those with Visual Snow may however see these phenomena more clearly and frequently irrespective of their age, or the physical condition of their eyes.
Changes in entoptic phenomena in this way have nothing to do with physical deterioration of the eye if they come together with Visual Snow. Physical deterioration can of course however occur irrespectively.
So while these phenomena can be annoying and at times more noticeable than the actual Visual Snow, they are not a cause for panic.
Most complaints about Entoptic Phenomena seem to be about blue field entoptic phenomenon and floaters, these may be sometimes confused for each other and blue field entoptic phenomenon may in cases be confused for Visual Snow.
Blue Field Entoptic Phenomenon is related to blood flow within the retina. These are white blood cells flowing through the eyes that can occasionally be seen against light surfaces. You may see them sometimes after a rapid change in blood flow (e.g. taking a quick shower). They are completely harmless and usually visible for only a number of seconds.
«Floaters» can be a range of things such as dust on the retina, bits of protein, or white blood cells. Once again these scenarios are all harmless.
In the less likely scenario that you you were to have a retinal blood leak you may see red blood cells across your visual field; those would be black but also unrelated to your Visual Snow.
Photophobia (light sensitivity) is one of the additional symptoms in the clinical classification of Visual Snow Syndrome. The area of hypermetabolism within the lingual gyrus may correlate to photophobia, but this is not known for sure – photophobia can have various causes.
In my experience light sensitivity along with Visual Snow can take detail and contrast away from the visual scene and create a blur-like effect.Those with Visual Snow and photophobia may not be able to see crisp details and may experience problems with their spatial reasoning and depth perception.
Increased glare, and also the bursting of lights (as «starbursts» and «halos») can feel physically intrusive and unpleasant.
Of the two main types: Illusory and Hallucinatory, those with Visual Snow seem to experience Illusory Palinopsia.
This is not afterimages in the classical sense of looking at a bright light and seeing a coloured/negative afterimage. Generally this is seeing positive afterimages and from weaker stimuli.
For example everyday text on a page of paper or a computer screen can heavily interfere with reading – words may even project onto walls.
So called «trailing» is another type of afterimage sometimes seen from moving objects (I do not experience this)
Those with Visual Snow and nyctalopia may struggle to see during the night and can almost be blind under certain light conditions.
Other Visual Symptoms
Sometimes those with Visual Snow can experience pulsating vision. This again probably relates to a heightened awareness of entoptic phenomena.
Pattern glare is believed to be a symptom of «visual stress». A heightened perception of which may reasonably be part of Visual Snow Syndrome as those with «cortical hyperexcitability» appear more sensitive to it.
Self Light Of The Eye
«Self light of the eye» is an entoptic phenomenon reported among those with Visual Snow.
Sometimes those with Visual Snow can see flickering in their vision either as a shutter or heatwave ripple effect.
It may sometimes be possible to experience what seems like other Visual-Snow-like Phenomena that are not persistent or uniform. These can probably be referred to as just «Visual Noise». Below are my attempts to depict some of these.
The first example appears to relate to retinal blood flow again, as it seems to occur in response to orthostatic changes. Alternatively if I rub my eyes I can also sometimes see these blue static along with phosphenes. I also see them if I start to feel faint – for example if I am out of condition at the gym or like recently when I cut my finger quite badly.
The second example photo combines two phenomena – seeing patches and seeing small specks of static – in my experience these may relate more to lighting conditions and adaptation problems.
Spontaneous Photopsia/Flashes Of Light
These three listed below are entirely normal phenomenon and not associated with Visual Snow but may cause worry if not known about.
Visual perception informs cognition plus other sensory perception (and vice-versa), so it is not strange to think that those with Visual Snow can have non-visual symptoms that they associate with their condition. Some of the common non-visual symptoms are discussed below.
Tinnitus is persistent noise in the ears. Visual Snow and tinnitus in those with Visual Snow may share a common origin. It is a very commonly reported comorbid symptom and like Visual Snow, tinnitus seems to be a factor of attention.
As you’d probably expect there is a connection between balance (the vestibular system), vision, and the other senses. Therefore those with Visual Snow may sometimes experience trouble with their balance/gait, or even encounter vertigo.
Depersonalisation/derealisation, anxiety, depression, ADHD are just some of the psychiatric symptoms that frequently follow with Visual Snow.
It is understandable that a change in one’s sensory perception has the potential to change your entire perception of the world, or of yourself. There may be direct physiological consequences such as changes to cognitive networks that lead to these sorts of symptoms.