| Identifier |
visual_snow_lee_novel |
| Title |
Visual Snow |
| Creator |
Andrew G. Lee, MD; Spencer Barrett |
| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (SB) Class of 2022, Baylor College of Medicine, Houston, Texas |
| Subject |
Visual Snow; Visual Static |
| Description |
Summary: • Visual Snow o Definition and Description > "snow" or "TV static", highly dependent upon patient symptoms > Online tools available for visual representation o Exam Findings > Exam is grossly normal > PET/MRI -hypermetabolism in lingual gyrus > Otherwise no clinical findings o Possible Etiologies > Exact etiology unknown > Migraine, subclinical seizure, "gain" problem, hyper-awareness of normal phenomenon o Possible Management Options > Anti-seizure medications have shown some efficacy > No definitive or clinically proven options available > FL 41 filtered lenses |
| Transcript |
So, today we're going to talk about visual snow, and the snow people see - what they describe as "snow" or "static," like a broken television screen - it's diffuse and bilateral. It kind of just fills their visual field. There's a snow simulator online that you can google, and the patients can choose their flicker rate, the size of the grains of snow, how fast it's blinking, and all sorts of parameters. It's mostly useful to show patients that other people have what they have, but also it lets the patient show you in a visual format what they're seeing. The visual snow can come on acutely; it's usually chronic. The patients are usually a little bit hyper-attentive. It's diffuse, bilateral, and the same between the two eyes. It doesn't normally cause any degradation in visual acuity. The pupil exam and the rest of the structural eye exam is normal. The imaging studies are usually normal; you could do an EEG to look for a seizure activity, but almost always it's normal. PET scans and functional MRI scans in the "visual snow people" have shown hypermetabolism in the lingual gyrus, so there is a radiographic correlate to what they're describing as "visual snow". It's not clear what causes this; some people believe it's migraine. Some people feel it's like a subclinical form of seizure. Other people just think it's a "gain problem". The "gain" is not set properly, so they can see what you can't see. In reality, I think normal people can appreciate snow if they stare at a wall that's blank like this long enough, you'll see the kinds of things that they see and describe this "visual snow". Most people just want reassurance that it's not something bad. I think there have been treatments that have been tried (Diamox, Depakote, anti-seizure medicines, topamax). All of these things have been tried, but nothing is really proven to be a cure. If you look at the diagnostic criteria, it requires that you don't have anything else. You have to have a normal examination, and some of the patients actually have migraine criteria. Some patients actually have apalinopsia. They have the perception that the image is repeating, often a trailing- palinopsia, for example where your hand is moving, they can see five or six of these hands. Some of the patients have had exposure to hallucinogens. Those are different kind of visual snow, which is a hallucinogen persistent perception disorder (HPPD) in the DSM 5. I think that most of these patients just have hyper-awareness of what is a normal phenomenon, but I believe them when they say they're symptomatic. So if we can turn down the gain with medicines, I think it might be helpful to them. We also use the filters. I have no proprietor interests, but we like the FL41 filters. Presumably, there's some mediation of the trigeminal-thalamic pathway here, so FL 41 filters sometimes help some people adjust. So I believe visual snow is real. It's bilateral, diffuse. It's constant. It's described as "snow" or "static" in the visual field of these patients. They have normal exam, normal imaging, and no evidence of seizure activity. You could try anti-seizure medicines as a trial. |
| Date |
2021-04 |
| Language |
eng |
| Format |
video/mp4 |
| Type |
Image/MovingImage |
| Collection |
Neuro-Ophthalmology Virtual Education Library: Andrew G. Lee Collection: https://novel.utah.edu/Lee/ |
| Publisher |
North American Neuro-Ophthalmology Society |
| Holding Institution |
Spencer S. Eccles Health Sciences Library, University of Utah |
| Rights Management |
Copyright 2019. For further information regarding the rights to this collection, please visit: https://NOVEL.utah.edu/about/copyright |
| ARK |
ark:/87278/s6kx1cp0 |
| Setname |
ehsl_novel_lee |
| ID |
1680638 |
| Reference URL |
https://collections.lib.utah.edu/ark:/87278/s6kx1cp0 |
