| Identifier |
Positive_visual_phenomenon_Part_II_Charles_Bonnet_Visual_Snow_Palinopsia |
| Title |
Positive Visual Phenomenon II: Charles Bonnet, Visual Snow, Palinopsia |
| Creator |
Andrew G. Lee, MD; Meesha Khatker |
| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (MK) Class of 2020, Baylor College of Medicine, Houston, Texas |
| Subject |
Positive Visual Phenomena; Charles Bonnet; Visual Snow; Palinopsia; Hallucinations |
| Description |
Dr. Lee lectures medical students on positive visual phenomena (part II). |
| Transcript |
So we talked about positive visual phenomena that come and go. There are other positive visual phenomena that you need to know about and one of them is a formed visual hallucination called a Charles Bonnet phenomenon. So as opposed to an illusion where you see something but misinterpret what you're seeing, a hallucination has no visual stimulus. So, Mr. Charles Bonnet's grandfather had vision loss, and then after that he started seeing people - like a man with a stovepipe hat…and so the Charles Bonnet phenomenon people have vision loss. It doesn't matter what their cause is, usually its moderate to severe but can be as little as 20/40 vision loss. They see formed visual hallucinations - people, animals, sometimes geometric figures, sometimes they're unformed but usually it's people. They should be able to recognize the unreal nature of the phenomenon…that is, they're not paranoid or crazy, they know its not real. They shouldn't talk and the person normally doesn't talk to them, so there is no auditory component. And there is no delusional construct. There's no backstory of why the people are there, they don't know the people, there's no story behind it. So the Charles Bonnet is a form of visual hallucination, it's a release hallucination, you know - an awake and alert patient who has no other reason to have it, and its usually a formed visual hallucination from vision loss. Visual Snow is a different type of phenomenon where patients see this pixilation that is usually diffuse throughout their entire field of vision and they describe it like "looking through snow." Its's usually both eyes, simultaneous and persistent, although its different under different lighting conditions. Visual snow is probably just increased sensitivity to an existing visual phenomenon that most people ignore. But some people are bothered by this. Normally we don't scan it or do any tests for it, but you could do an MRI and EEG to look for a cause. But mostly it's benign. There are a number of treatments that have been tried, mostly anti-migraine therapy and anti-seizure therapy, but it's generally benign. Most people just want to know that they're not crazy. Again, like Charles Bonnet there is no delusional construct behind it - they recognize the unreal nature of the phenomenon. And there is this last visual phenomenon I want to tell you about, which is called Palinopsia. "Palin-" means "repeat" and "-opsia" means "see." So a patient sees the same image over and over again - a repeating image. So you might see a house and then you see the same house. It can also be a trailing palinopsia - so they see their hand and then when they move their hand they still see their hand (or 3 or 4 hands). This is occipital in origin. The most common cause is….no cause. However, any lesion in the occipital cortex can produce it. Strokes, seizures, tumors. And I generally do an MRI and an EEG for the palinopsia patients. A lot of patients have used hallucinogens in the past and it comes back, it's like a flashback. The most common is LSD. We call it a persistent positive disorder from hallucinogen. A "hallucinogen persistent positive disorder." And palinopsia is a common feature, so you should ask about prior hallucinogen use - LSD, magic mushrooms, whatever they used. Some palinopsia patients have been exposed to medicines that were used for some other indications. Topiramate, clomiphene - Clomid is the fertility drug. So you should ask about medicines in patients with palinopsia. So these are 3 special forms of unusual visual phenomenon that sound crazy but are absolutely real. |
| Date |
2019-03 |
| 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/s63c0ccq |
| Setname |
ehsl_novel_lee |
| ID |
1404090 |
| Reference URL |
https://collections.lib.utah.edu/ark:/87278/s63c0ccq |
