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Clinical Conundrums: Case History 4 – Charles Bonnet Syndrome
I first came across Charles Bonnet Syndrome as a symptom in association with age related macular degeneration but it wasnât until I worked as a specialist low vision optometrist that I realized how common and significant a problem it was.
I was performing low vision assessments, when one day a 78 year old lady presented to me very distressed and confused. She was worried that her family thought she was going âmadâ? because she was frequently seeing the image of a black cat, similar to the one she had previously owned as a pet many years ago. She had been seeing the vivid image of the cat for the last year, almost every day at different times. Her family were becoming increasingly concerned as to the state of her mental health. However, I was able to reassure her that this was common and was a subsequent complication of her visual loss.
Charles Bonnet Syndrome (CBS) has a prevalence of between 10 – 15% in patients with visual impairment. It was named after the Swiss naturalist and philosopher Charles Bonnet. He reported hallucinations of men, women, birds and buildings in his cognitively healthy grandfather who had become blind due to cataracts. 
CBS means to see visual hallucinations and tends to affect patients who have lost their sight, usually later in life but can occur at any age. The causes can be due to dense inoperable cataracts, age related macular degeneration, retinal detachment and other sight threatening conditions.
A visual hallucination is by definition a false perception of something that is not really there, hallucinations may be visual or auditory. They may occur as a consequence of various medical, neurological, ocular and psychiatric disorders and drug induced hallucinations. They can be caused by anomalies of almost any part of the visual system.
A hallucination can be classified as either:
(A) simple or
(B) complex.
Simple hallucinations includes photopsia, lines, zig zags etc. Commonly found in PVD, migraine, optic neuritis and occipital lobe tumors.
Complex hallucinations include well formed images i.e. animals, faces or environmental settings occurring more commonly in dementia, Parkinsonâs disease schizophrenia and misuse of recreational drugs
The significant difference between CBS and mental impairment is that in CBS the patients know that the image isnât real, while those associated with mental conditions, often believe that the image is real.
CBSÂ is believed to occur following patients losing their sight, therefore their visual cortex is no longer receiving as many images as before, so to compensate new images or even old images previously stored are released and perceived as if they are been momentarily seen, these episodes often occur when the patient is in a relaxed state i.e resting or in bed
At present there is no cure or treatment for CBS. However, knowledge that it is poor vision and not mental illness that causes these problems can be very reassuring and often helps people come to terms with them. In general the hallucinations last for a year to eighteen months and can be exacerbated by a period of visual loss. The primary treatment includes treating the cause of vision impairment, but in many cases this is not possible. Non-pharmacological interventions, such as increasing the lighting at home and reducing social isolation by encouraging more social contact, are known to be helpful.
Further reading:
1. The Royal NationalInstitute for the Blind – Charles Bonnet Syndrome
2. Macula Vision Research Foundation -Charles Bonnet Syndrome
3. Charles Bonnet Syndrome – Elderly People and visual hallucinations – Jacob et al 2004
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Simon Frackiewicz // Jun 4, 2007 at 2:33 pm
Many thanks for your fascinating article about Charles Bonnet Syndrome, a subject I too find very interesting. I have an elderly patient with bilateral wet ARMD who sees elaborate, cartoon-like images in her central vision, particularly at night, which has been worsening since the onset of vision loss ten years ago. It remains an annoyance for her (and a source of interest for me), but is something she is learning to live with.
I would add to the Further Reading list a fascinating book by VS Ramachandran entitled ‘Phantoms in the Brain’, a collection of neurological case studies including CBS and other higher-order visual disorders.
Thanks again
Bill McMellon // Jul 3, 2007 at 5:41 am
Hello
I am a Social Worker in an Older Peoples’ Mental Health Team, trying to support some-one with Bonnet Syndrome. Is there any-one out there with experience of CBT in this connection? I would be interested to hear from any-one using this (or other psycho-social interventions).
Best Wishes, Bill McMellon.
Sue // May 14, 2008 at 12:04 pm
I have these hallucinations. I always thought that it was because I was psychic. Like a couple of months ago I saw a cartoon like image of someone filling up a car at a gas station. I don’t own a car and never have occasion to do this. Then the gas prices started to increase.
However, I did have surgery on my eyes as a child for strobismos and do not have normal vision, so I don’t drive.
Does this mean I am in danger of losing my eyesight?
I also have migraines with aura.
Frank E // May 19, 2008 at 3:21 am
Sue,
Hallucinations due to Charles Bonnet syndrome are most common in older people (60 and above) who in their later years have acquired an eye disease which has dramatically reduced their vision.
Although you mention that you do not have normal vision and have had strabismus surgery when a child this is not likely to result in Charles Bonnet type hallucinations.
I would advise you to see your general practitioner and explain that you are having hallucinations and then have further tests arranged to determine their cause.
L Perry // Apr 7, 2009 at 5:55 pm
I have what appear to be snowflakes appearing at he sides of my eyes when I enter a dark street which has street lighting.The optician has no idea what is causing this, saying that seh has never known this before. What can it be.
Jane Macnaughton // Apr 8, 2009 at 5:29 pm
Hi LPerry,
I am sorry, that we are unable to answer questions regarding personal symptoms on this site.
Joyce Webb // Apr 18, 2009 at 9:35 pm
Yes I am 78 andwas diagonosed with wet macular in my right eye in 2002. had PDTreatment 2 session and some Laser. Early on I was frightening by strange visions, i.e. clown heads, avenues of popular trees, but then reading up was able to put a name to the condition.. It disappeared after several months.At the time I thought I was going mad,but then realised it was a rather interesting condition.
Mary Brown // Jul 1, 2009 at 3:17 pm
My 90 yr old father had a BCC surgically removed from his lower eyelid – a process which involved grafting a skin flap from the upper lid and his right eye being sewn closed for many weeks. He experienced the hallucinations (people, moving patterns etc) described as Charles Bonnet Syndrome although we did not have a name for them at that time. He repeatedly reported these experiences to the health care professionals he met but they took no interest. Reassurance that he was still sane would have been nice but he was also concerned that others undergoing the same procedure could be warned of this side-effect. The operation was successful and his sight restored and he now has no hallucinations. I hope that other elderly people will have met with a more sympathetic approach.
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