in Psychiatric Eponyms

Charles Bonnet syndrome


Charles Bonnet syndrome is a cause of complex visual hallucinations.  The core features are the occurrence of well formed, vivid, and elaborate visual hallucinations in a partially sighted person who has insight into the unreality of what he or she is seeing.  Its prevalence in patients with visual impairment varies from 10% to 15%.  To diagnose the condition there should not be features which might lead to an alternative explanation such as psychosis, dementia and intoxication.

The syndrome occurs most commonly in elderly people, probably because of the prevalence of visual impairment in this group. The common conditions leading to the syndrome are age related macular degeneration, glaucoma and cataract. The hallucinations may last from a few seconds to most of the day and may persist for a few days to many years, changing in frequency and complexity. Many patients can voluntarily modify them or make the image disappear if they close their eyes.. The imagery has no personal meaning and is varied and may include groups of people or children, animals, and panoramic countryside scenes.

The condition is named after the Swiss naturalist and philosopher Charles Bonnet. He reported the hallucinations of Charles Lullin, his 89 year old otherwise healthy and cognitively sound grandfather, who was blind owing to cataract and yet vividly saw men, women, birds, and buildings.

There is no definitive treatment for the condition but it is reported that reassurance and explanation that the visions are benign and do not signify mental illness has a powerful therapeutic effect. Hallucinatory activity may terminate spontaneously, on improving visual function or on addressing social isolation. There is no universally effective drug treatment but anticonvulsants may play a limited role.

Read more:

Charles Bonnett syndrome – elderly people and visual hallucinations – excellent BMJ paper (paywall)
Complex visual hallucinations in the visually impaired: the Charles Bonnet Syndrome.
Charles Bonnett Syndrome – Wikipedia

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  1. How strange you should write about this now – I was talking about this with my Counsellor a week ago. My Mum had macular degeneration, and showed what I thought might be signs of having Charles Bonnett Syndrome. With hindsight it may well have been early signs of the dementia she died of later in the year. I do note that you mention exclusionary disease. If you’re interested you can read my blog entry about it:

    Will now go and read the papers you mention, thanks for the memory and reminder of a strange syndrome!


  2. This is interesting because my eye condition [not CBS] in part caused me to go mad in my youth and I’m just learning that some of my visual perceptual differences might be attributed to my eyes and not my voices. This raises many questions for me regarding the sight/mental health interface which can be left by the way side in psychiatry. Even when it was noticed I was reading 2″ away from my face that didn’t seem worthy of any discussion. There have been some AJP papers tring to link Keratoconus with Schizophrenia or to define a ‘Keratotonic personality’ but I reckon us folk with wonky eyes might be more inclined to lose the plot simply because it’s distressing to not be able to see well or have visual distortions.

  3. I have been diagnosed with this condition for a long time, since I was 15 years old, I am now 23. My eyesight is perfect, however,which does lead me to wonder why it is so prevelent in my case- I do suffer from an enlarged Pituitary gland which swells and returns to normal every so often, perhaps this explains it?