Photo by: Wojtek Pacześ from Pexels / 2020
Take a second to lift your eyes from the screen, and let them rest on a nearby wall. Does your view appear smooth, clear and unobstructed? Or do you notice something faint, flickering like television static – hundreds of tiny dots crackling in and out of view? If it’s the latter, you may be part of the two percent of people in the UK who experience visual snow, a newly recognised visual condition in which a layer of ‘TV static’ stands between the observer and their visual world.
Visual snow was first described in 1944, when the physician Frank D. Carroll administered digoxin, a medication derived from the foxglove plant (Digitalis lanata) and commonly used to treat heart conditions, to his patients. To his surprise, they reported a series of bizarre visual effects; images of flowers seemed to appear, objects became tinged green and yellow, and they complained of ‘snowy vision’. Concerned and fascinated, Carroll conducted thorough eye examinations for his patients, all of which came back normal. The problem had not been with the eyes, but with the brain.
Contrary to our intuition, our eyes are responsible for only a small part of what we call ‘seeing’. Instead, they act as catching mitts, capturing a flood of raw light signals which the brain then assembles into a coherent visual image. Billions of highly specialised neurons–some detecting straight lines, others detecting colours or depth relations–work together to build a representation of our surroundings, forming the everyday ‘visual world’ we know so well. Conditions like visual snow arise when this process of construction goes awry, whether temporarily, as with certain drugs like digoxin, or permanently due to neurological differences. The brain mistakes non-light signals for light, incorporating these false positives into perception and producing the flickering ‘static’.
In severe cases, this static can dominate vision and trigger migraines, making everyday tasks challenging. Visual snow falls into the same category of ailments as tinnitus, in which the brain perceives sounds that aren’t there, and neuropathy, where it generates illusory pain signals. These ‘diseases of consciousness’ reveal the gap between high-level cortical awareness — the part of the brain that recognises these perceptions as illusory — and the lower-level mechanisms of our early perception that continue producing them regardless. The frustration over this disconnect is evident in the online communities that visual snow sufferers have flocked to in a desperate search for relief in homemade ‘cures’.
One such community is r/visualsnow on Reddit, where discussions range from SpongeBob memes about ruined views of the sunset to intense debates among users who seem well-versed in neuroscience, arguing over which neurotransmitters play the central role in causing symptoms. One user comments, “It’s GABAergic inhibitory inputs on 5-HT2A receptors. It’s why both serotonergic agonists and antagonists make it worse for a lot of us.” Another replies, “I don’t think people understand how GABA in the thalamus works,” and in a separate thread even suggests trying an expensive, experimental supplement.
While taking medical advice from strangers over the internet might seem ill-advised, many have turned to these forums due to the medical profession overlooking visual snow for most of its history. Lack of awareness has led to patients receiving near-constant misdiagnoses and mistreatment. Such was the case for Sierra Domb, who, after being prescribed medication which worsened her symptoms, founded the Visual Snow Institute in 2018. Its mission is to connect vision scientists globally to raise awareness and improve understanding of the condition. Since then, research into visual snow has quadrupled, and just this year, the World Health Organisation assigned formal classification codes to the disorder, marking a major milestone in its recognition.
Since the Institute’s founding, research into this disorder has made significant advances. Recent research shows visual snow symptoms arise not from a single brain region, but from the interaction of complex neural networks. The condition can develop at any age, and key neurotransmitters such as glutamate and serotonin play fundamental roles. While treatment options remain elusive, research progress is steady, offering hope for sufferers. More broadly, such efforts by researchers are a cause for optimism: while science’s relentlessly objective lens can sometimes be said to strip the world of its subjective beauty, the diligent work of hundreds of vision scientists shows that, for those with visual snow, it is also hard at work to restore it.
Written by Shaun Henderson, a fourth-year Psychology student at the University of Edinburgh, interested in the study of visual perception.
Article edited by Priscilla Wong, a Fourth-Year Biological Sciences (Immunology) student at the University of Edinburgh, and an Online News Editor for EUSci.
References:
Digitalis produces visual snow symptoms:
- Carroll, F.D. (1945). Visual Symptoms Caused by Digitalis. American Journal of Ophthalmology, 28(4), pp.373–376. doi:https://doi.org/10.1016/0002-9394(45)90940-8.
Visual Snow involves glutamate and serotonin abnormalities:
- Puledda, F., Dipasquale, O., Benjamin Jm Gooddy, Nazia Karsan, Bose, R., Mehta, M.A., Williams, S. and PJ Goadsby (2023). Abnormal Glutamatergic and Serotonergic Connectivity in Visual Snow Syndrome and Migraine with Aura. Annals of Neurology, 94(5), pp.873–884. doi:https://doi.org/10.1002/ana.26745.
Visual Snow onsets at any age:
- Puledda, F., Schankin, C. and Goadsby, P. (2020). Visual snow syndrome A clinical and phenotypical description of 1,100 cases. American Academy of Neurology. [online] doi:https://doi.org/10.1212/WNL.0000000000008909.
Visual snow involves widespread network connectivity differences:
- Strik, M., Clough, M., Solly, E.J., Glarin, R., White, O.B., Kolbe, S.C. and Fielding, J. (2022). Brain network dynamics in people with visual snow syndrome. Human Brain Mapping, [online] 44(5), pp.1868–1875. doi:https://doi.org/10.1002/hbm.26176.
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