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    Seeing through the static

    Take home message: Visual snow is a persistent visual disturbance that is typically described as seeing ‘television static’ throughout the visual field.

     

     

    The Neuro-Connection By David Gersztenkorn, MD, and Andrew Lee, MD

    A fascinating article was recently published which described visual snow syndrome, a collection of refractory symptoms including visual snow (‘television static’), palinopsia (Greek: palin for ‘again’ and opsia for ‘seeing’), and entoptic phenomena.1,2

    Patients generally describe visual snow as a grainy pattern throughout their visual field similar to analog television noise (Figure 1).

    The ocular and neurological exams and neuroimaging studies are unremarkable, and the differential diagnoses include migraines, concussions, prescription drug side effects, and hallucinogen persisting perception disorder.

    Although generally considered to be benign, many patients report that persistent visual disturbances of visual snow syndrome are quite distressing and markedly affect their activities of daily living. While not described as ‘television static’ per se, we did find reports from over 50 years ago that describe similar symptomology such as looking through “shimmering mistiness” and “foggy vision” throughout the entire visual field.3,4

    A literature search did not reveal any articles that characterized such symptoms before the invention of the television. It is interesting to consider if there is an association between the amount of television an individual watches throughout childhood or adulthood and the development of visual snow. Although it is not clear if people are born with the neural circuitry that can generate these visual disturbances, asymmetry between the right and left occipital lobes (occipital bending)5could also be a risk factor for visual snow.6

    Some of our younger patients notice that the visual snow phenomenon is exacerbated while working on the computer and when using their smartphones. There are patients who report that changing the screen’s refresh rate and background illumination mitigate symptoms, while others note that wearing FL-41 or ‘rose-tinted’ lenses helps relieve their discomfort.7

    It could be beneficial to study visual snow in the context of the psychophysics of contrast-tuning and gain-control. Structured evaluation and analysis of sensory processing in patients with visual snow could also provide insight into mechanisms of contrast adaptation, light sensitivity, and photophobia.

    “Vision rehab” strategies such as visual habituation and visual adaptation have proven useful in treating conditions such as visual vertigo, and we wonder whether the use of analogous behavioral treatment approaches could help alleviate the distress of visual snow. 

     

    References

    1.         Schankin CJ, Maniyar FH, Digre KB, Goadsby PJ. 'Visual snow' - a disorder distinct from persistent migraine aura. Brain. 2014;137(Pt 5):1419-1428.

    2.         Gersztenkorn D, Lee AG. Palinopsia revamped: a systematic review of the literature. Surv Ophthalmol. 2015;60(1):1-35.

    3.         Kinsbourne M, Warrington EK. A study of visual perseveration. Journal of Neurology, Neurosurgery & Psychiatry. 1963;26(5):468-475.

    4.         Klee A, Willanger R. Disturbances of visual perception in migraine. Review of the literature and a report of eight cases. Acta Neurol Scand. 1966;42(4):400-414.

    5.         Maller JJ, Thomson RH, Rosenfeld JV, Anderson R, Daskalakis ZJ, Fitzgerald PB. Occipital bending in depression. Brain. 2014;137(Pt 6):1830-1837.

    6.         Unal-Cevik I, Yildiz FG. Visual Snow in Migraine With Aura: Further Characterization by Brain Imaging, Electrophysiology, and Treatment - Case Report. Headache. 2015.

    7.         Wilkins AJ, Patel R, Adjamian P, Evans BJ. Tinted spectacles and visually sensitive migraine. Cephalalgia. 2002;22(9):711-719.

     

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