Continuously present positive visual phenomena throughout the visual field in the form of countless flickering/moving dots. A pan-field visual disturbance described as tiny flickering dots, which resemble the static noise of an untuned television.
Often the dots are black or white, but different colors are also reported. Patients describe it as TV static or looking through a heavy rain and some patients also see it with eyes closed.
This neurological disorder is named after this hallmark symptom.
(+ at least 2 of the following 5 symptoms to be considered as Visual Snow Syndrome)
Palinopsia (After Images and Ghosting)
Palinopsia, meaning: ‘seeing again’, is a continuous or repetitive visual perception after the actual stimulus is no longer present. An inability to suppress the just-seen (Critchley, 1951). It is a broad term and it can be divided into: Illusory- and hallucinatory palinopsia.
VSS patients experience the illusory palinopsia. The cause is still unknown, but researchers think it may be related to the hypometabolism in the inferior parietal lobule (Schankin, et. al., 2020). Palinopsia differs from the ‘normal’ retinal afterimages, which only occur when staring at a high-contrast image and are in complementary color (Schankin, et. al., 2020).
Palinopsia can also be part of another condition, which is why it is advisable to see an ophthalmologist and neurologist.
- After Images:
A very common and for some a debilitating symptom. Reading can be challenging, because letters/text can project onto other surfaces.
Moving images can cause trails.
An intolerance of light(sources). ‘Normal’ light is causing pain or discomfort in the eye or head. VSS-patients suffer from a persistent photophobia which is similar to chronic migraineurs during attacks (Eren, et. al., 2019 Quantification of photophobia in visual snow syndrome: a case-control study). Sometimes photophobia is accompanied by allodynia (non-painful stimuli are painful).
Glare is difficulty of seeing in the presence of bright light(sources). It often impairs the vision. All individuals are affected by glare at some point but those problems are intensified in VSS-patients. It causes huge discomfort or even pain in some cases.
Bright circles that surround a light source, like headlights. Everyone can experience Halo’s, but VSS-patients see this more intensely and it can even be painful for the eyes.
A scattering of light from the light source that can cause huge discomfort. VSS-patients see a more intense and brighter starburst than healthy controls.
Enhanced entoptic phenomena
With the emphasize on ‘enhanced’. Entoptic phenomena is a broad term and means ‘phenomena inside the eye’. Of course, this may make it appear as though there are ophthalmic abnormalities, however ophthalmological examination is usually not abnormal in VSS-patients with this symptom. Everyone experiences ‘entoptic phenomena’, but because VSS-patients have a hyperexcitability of the brain, entoptic phenomena are more intense and also more visible to them. Researchers think it’s because of a broken filter in the VSS brain. But we strongly recommend, that if you experience these symptoms and not knowing its cause, to see an ophthalmologist and neurologist. The most common entoptic phenomena are BFEP and floaters.
- Blue Field Entoptic Phenomenon
BFEP is often confused with the Visual Snow / static itself. It appears as tiny white dots moving quickly along squiggly lines within the entire visual field. This BFEP can be visible to anyone, but VSS-patients see this on a much more intense scale. BFEP is related to blood flow in the retina and it contains white blood cells moving. This is harmless.
Worm-shaped liquid blobs in the eye. This symptom is also often confused with the static from VSS. Everyone can experience this, but for VSS-patients this is also much more present. Floaters are turbidity (dust or protein) on the retina. This is also harmless.
VSS-Patients may experience night blindness. Contrasts are often less clear.
Other visual symptoms that can occur:
Some patients experience a flicker of light in their field of vision. This may be very occasional to frequent. It can be triggered by the sudden change from light to darkness. Such a symptom should always be reported to a physician, as it may also occur as another disorder/disease (epilepsy for example). It can also be a retinal detachment If it occurs all of a sudden. Then it is necessary to contact a doctor a.s.a.p.
The visual field seems to pulsate like breathing. It is probably due to an enhanced entoptic phenomena. Some people describe it as a continuous heatwave effect.
Also known as ‘visual stress’ (which has nothing to do with actual stress). A discomfort and anomalous visual perceptual distortions when observing patterns of stripes with certain spatial characteristics. This symptom is also common in migraineurs. According to research* (link naar Monger et. al., 2015, Pattern Glare: the effects of constrast and color). the cause is believed to be the hyperexcitability of the visual cortex.
Self light of the eye
Some patients describe it as seeing a sort of lava lamp with their eyes closed.
Non-visual symptoms that can occur
A sensation of motion (most commonly rotational motion). A symptom of vestibular dysfunction.
Persistent postural-perceptual dizziness (PPPD)
PPPD is a common chronic dysfunction of the brain and vestibular system that produces persistent dizziness, non-spinning vertigo and/or unsteadiness. It’s often related to migraine and VSS. All three are disorders of sensory processing.
Hypersensitivity to normal everyday sounds. Certain sounds are perceived as very unpleasant or even painful. These are often high-pitched loud noises.
An unusual feeling of tiredness. Not comparable with normal tiredness.
Migraine reinforces VS and VSS. One obviously suffers more when dealing with both.
Constant bilateral ear noise that patients describe differently. The tone can be constant or variable. Some describe it like the sound of an old CRT TV. According to the study ‘Visual Snow Syndrome and Its relationship to Tinnitus 63% of the patients suffered from tinnitus. It suggests a common underlying pathophysiology’. This study suggests that VSS may be related to other sensory processing disorders, such as Tinnitus.
There is no exhaustive list of symptoms, but here are the most common ones. Each VSS patient is unique and because VSS has no grades (yet) many cases fall under one heading. Much is also still unknown in the field of VSS, since it is relatively new and much research is still needed.