Visual Snow (VS)
Marsha Sorenson, OD• Timothy C. Hain, MD•Page last modified:
May 17, 2022
Visual Snow syndrome consists of the perception of "snow" -- namely dots, pixellated fuzz, bubbles or static in vision (Ciuffreda et al, 2019). There has been considerable interest in this phenomena recently(Puledda et al, 2018), possible related to social media buzz. Prior to 2014, there were fewer than 10 cases in the entire medical literature (Metzler and Robertson, 2018).
Visual Snow is often found in combination with Migraine. It is sometimes accompanied by four other phenomena:
- palinopsia, "the persistence or recurrence of visual images after the stimulus has been removed," (Gersztenkorn and Lee, 2015).
- It is thought palinopsia is a result of a disruption of ?saccadic suppression? or the brains inhibitory response to prevent multiple images on the retina while objects are in motion
- photosensitivity (or photophobia),
- Photosensitivity refers to being abnormally light sensitive.
- Nyctalopia is difficulty seeing at night, this symptom seems to be noticed most while driving at night.
- Enhanced entopic imagery
- Enhanced entopic imagery refers to images that are normally transient taking longer to go away than what is normal, or being more noticeable to the patient than what is normal. Camera flashes, after images from lights, and vitreous floaters would be examples.
VS is also associated with tinnitus. (White et al, 2018) The association of tinnitus with visual snow obviously suggests that it reflects a disorder broader than the visual system alone.
In patients with migraine, these symptoms may represent just a part of the general tendency to have greater responses to sensory inputs than normal.
- van Dongen et al (2019), reported that frequent comorbid conditions include "migraine, tinnitus, and psychiatric conditions including depression and anxiety. "
- Chen et al (2019) reported a single patient with Creutzfeldt-Jakob. We think this was just a coincidence.
- Renze M, reported in the International J. Tinnitus (2017), that 63% of patients with visual snow also have continuous bilateral tinnitus. We think this is likely an overestimate, as we are doubtful that tinnitus and visual phenomena have much overlap.
- White et al (2018) suggested that "There may be a number of syndromes associated with impaired sensory processing resulting in sensory misperception, including migraine, persistent perceptual postural dizziness, and tinnitus, which overlap with VSS." We think this is a bit of a broad conclusion. We cannot see why PPPD (a psychiatric syndrome), should be associated with changes in visual cortex.
- MItchell and Vierkant (1991) noted that "Cocaine abusers had a greater frequency of visual hallucinations (47 to 7), distinguished by shadows, flashing lights ("snow lights"), objects moving and bugs crawling on the arm.". Similar observations about cocaine hallucinations were made by Siegel (1978). This seems to be a real phenomena and there is likely some overlap between visual snow and cocaine hallucinations.
To evaluate visual snow, a complete eye exam is needed to rule out any ocular health problems. Additional testing including corneal topography, Optical Coherence Tomography (OCT) may be recommended to rule out other conditions. Saccadic eye movements should be evaluated to determine if a patient will benefit from vision therapy to reduce palinopsia.
There is also some data in the literature that the disorder is usually accompanied by a reduction of visual habituation, that can be detected using visual evoked potentials.
Chicago dizziness and hearing evaluates and treats patients with visual snow in our "visual vertigo" clinic.
Mechanism of visual snow
Visual snow is generally thought to be due to a central (brain) disturbance with lowered thresholds for perception in the visual cortex, or lack of habituation.
- Lauschke, J. L., et al. (2016). opined that "VS is a thalamocortical dysrhythmia of the visual pathway."
- McKendrick et al (2017) reported that "The visual snow group demonstrated reduced center-surround contrast suppression (p = 0.03) and elevated luminance increment thresholds in noise (p = 0.02).", and suggested that "data are consistent with elevated excitability in primary visual cortex;"
- Yildiz et al (2019) reported that "The loss of habituation and lower threshold for occipital cortex excitability were demonstrated electrophysiologically in VS patients. "
- White et al (2018) opined that "VSS is likely associated with either hyperactive visual cortices or, alternatively, impaired processing of simultaneous afferent information projecting to cortex."
- Luna et al (2018) stated "In contrast to the pattern of habituation observed in controls, visual snow was associated with persistent potentiation of the VEP response. ", in a study of a single case.
- Eren et al (2018) noted increased N145 latency and reduced N75-P100 amplitudes, and concluded "These findings are in agreement with the idea that the primary disturbance in VS is a dysfunction of the visual association cortex". Quoting them again -- "Visual evoked potentials from patients with VS demonstrated increased N145 latency (in milliseconds, VS: 152.7 +/- 7.9 vs M: 145.3 +/- 9.8 vs C: 145.5 +/- 9.4; F = 3.28; p = 0.046) and reduced N75-P100 amplitudes (in microvolts, VS: 7.4 +/- 3.5 vs M: 12.5 +/- 4.7 vs C: 10.8 +/- 3.4; F = 3.16; p = 0.051). " This is somewhat of an opposite idea as others-- a decrease in responses rather than an increase.
- Van Doorn and Koenderink (1982) discussed using random dot speck-patterns ("Julesz" patterns") for testing. One would think that this would be impaired in persons with visual snow. There are several papers by this group.
Treatment for visual snow can be broken down into ocular interventions and medicine.
Ocular interventions(Optometric treatments) to improve quality of life in patients with visual snow include tinted lenses and optometric vision therapy. Tinted filters may help reduce the perception of visual snow, changing light characteristics or decreasing luminance may reduce the appearance of visual snow. Gray, FL-41 (a shade of pink) or blue-blocking lenses (yellow) may help make visual snow less bothersome.
- Lauschke et al (2016), suggested that "Colour filters, particularly in the yellow-blue colour spectrum, subjectively reduced symptoms of VS. "
Medical interventions are usually medications that modify migraine, such as seizure medications. Examples include
- sodium valproate (not found helpful by van Dongen et al, 2019)
- lamotrigine (Bou Ghannon and Pelak, 2017, van Dongen et al 2019)
- Acetazolamide (Bou Ghannon and Pelak, 2017)
- flunarizine (not found helpful by van Dongen et al, 2019)
Review of papers regarding treatment of visual snow (not so many of these !):
- van Dongen et al (2019) reported that ' Of medication prescribed (lamotrigine, valproate, acetazolamide, flunarizine), only lamotrigine afforded some improvement in a small minority of patients"
- Bou Ghannon and Pelak (2017) reported positive results treating with lamitrogine (as high as 300 mg daily), acetazolamide (as high as 1000), verapamil (120-240)
- Unal-Cevik, I. and F. G. Yildiz (2015). reported a single case where lamotrigine improved rVEP.
Our experience with treatment:
At CDH, we usually consider visual snow to be related to migraine. Migraine contains within it a large number of sensory sensitivities, not always accompanied by headache, and with a larger repertoire of medications aimed to stabilize irritable cortical circuits. In one case, a man in his 30's complained of --
"symptoms are worsened by certain audio frequencies, or noisy locations like busy
restaurants. Unnatural light sources are a major problem. I originally thought fluorescent light was the
worst, but LED is AWFUL. I can perceive the high frequency strobing of LED lights, and it absolutely
drains me. Weather and/or changes in pressure can affect me. Sometimes even smells seem to set me off.
At its worst, stationary objects, especially patterns or text on posters will appear to shake or jiggle." The smell sensitivity is particularly suggestive of migraine (Kelman, 2004). His visual snow largely vanished after adding magnesium supplements to his regimen. Magnesium is generally safe, and helps in stabilizing neural circuits.
- Bou Ghannam, A. and V. S. Pelak (2017). "Visual Snow: a Potential Cortical Hyperexcitability Syndrome." Curr Treat Options Neurol 19(3): 9.
- Chen, B. S., et al. (2019). "Visual snow: Not so benign." J Clin Neurosci 64: 37-39.
- Ciuffreda, K., et al. (2019). "Visual Snow Syndrome (VSS): An eolving neuro-optometric clinical perspective." Visul Development and Rehabilitation 5(2).
- Gersztenkorn, D. and A. G. Lee (2015). "Palinopsia revamped: a systematic review of the literature." Surv Ophthalmol 60(1): 1-35.
- Kelman, L. (2004). "The place of osmophobia and taste abnormalities in migraine classification: a tertiary care study of 1237 patients." Cephalalgia 24(11): 940-946.
- Lauschke, J. L., et al. (2016). "Visual snow: A thalamocortical dysrhythmia of the visual pathway?" J Clin Neurosci 28: 123-127.
- Metzler, A. I. and C. E. Robertson (2018). "Visual Snow Syndrome: Proposed Criteria, Clinical Implications, and Pathophysiology." Curr Neurol Neurosci Rep 18(8): 52.
- Luna, S., et al. (2018). "Antagonistic Relationship Between VEP Potentiation and Gamma Power in Visual Snow Syndrome." Headache 58(1): 138-144.
- Mitchell, J. and A. D. Vierkant (1991). "Delusions and hallucinations of cocaine abusers and paranoid schizophrenics: a comparative study." J Psychol 125(3): 301-310.
- Puledda, F., et al. (2018). "Visual snow syndrome: what we know so far." Curr Opin Neurol 31(1): 52-58.
- Puledda, F., et al. (2020). "Visual snow syndrome: A clinical and phenotypical description of 1,100 cases." Neurology 94(6): e564-e574.
- Renze, M. (2017). "Visual Snow Syndrome and Its Relationship to Tinnitus." Int Tinnitus J 21(1): 74-75.
- Siegel, R. K. (1978). "Cocaine hallucinations." Am J Psychiatry 135(3): 309-314.
- Unal-Cevik, I. and F. G. Yildiz (2015). "Visual Snow in Migraine With Aura: Further Characterization by Brain Imaging, Electrophysiology, and Treatment--Case Report." Headache 55(10): 1436-1441.
- van Dongen, R. M., et al. (2019). "Treatment effects and comorbid diseases in 58 patients with visual snow." Neurology 93(4): e398-e403.
- van Doorn, A. J. and J. J. Koenderink (1982). "Temporal properties of the visual detectability of moving spatial white noise." Exp Brain Res 45(1-2): 179-188
- van Doorn, A. J. and J. J. Koenderink (1982). "Spatial properties of the visual detectability of moving spatial white noise." Exp Brain Res 45(1-2): 189-195.
- van Doorn, A. J. and J. J. Koenderink (1982). "Visibility of movement gradients." Biol Cybern 44(3): 167-175.
- Yildiz, F. G., et al. (2019). "The Clinical Characteristics and Neurophysiological Assessments of the Occipital Cortex in Visual Snow Syndrome With or Without Migraine." Headache 59(4): 484-494.
- White, O. B., et al. (2018). "Visual Snow: Visual Misperception." J Neuroophthalmol 38(4): 514-521.