What follows is an essay about the circumstances that led me to an interest in science communication in the first place. The syndrome described here is estimated to be relatively common among those with limited vision, you can find a lot of information about it on the web. Unfortunately, in order to search for information about it you need to know the syndrome exists. This essay is the result of my frustration that when Amy started seeing things no one told any members of the family about this possibility and by the time I did find out about it, our initial belief that Amy was suffering from dementia had tainted her trust in us. Had we known about it earlier the last five years of her life might have been easier for all involved. The original version of this essay was written for a science communication assignment.

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The deterioration may have begun after a botched cataract operation in her mid-80s, or it may have been age related macular degeneration, a common cause of vision loss as we all grow older. Most probably it was a mixture of both. Whatever the reason Amy’s vision deteriorated gradually through her late 80s to her mid-90s. It started off as a loss of detail in her central vision, faces of her friends and relatives looked blurry, the paintings on the walls lost detail, and most importantly, books became more and more difficult to read. Slowly she lost the ability to recognise colours or to see her own face in the mirror. All her hobbies relied on her ability to see. She loved reading murder whodunnits, painting pictures, knitting, and writing limericks but by the time she reached her mid-90s all these were no longer possible. She did listen to music and to audiobooks. She also continued making the once five-minute walk to the nearby supermarket to pick up the Listener magazine she could no longer read and the cakes that she always had available for the relatives and friends who regularly visited her. I was one of those visiting relatives, the second youngest of her nieces.

We were friends as well as aunt and niece, sharing a love of reading and writing. I found it hard to watch the shrinking of her once vibrantly visual world. It was even harder for Amy who had to experience that shrinking every moment of every day. But there was another, more insidious problem, that concerned me and the rest of the family about Amy, she appeared to be showing signs of dementia.

Amy had started seeing things. Lights appeared on the road outside her house. She thought they belonged to a car that for some reason always decided to park there at night. A couple of times she saw a cat jump down from her bed, she thought that a neighbour’s cat must have got into the house. On several occasions, she even saw two people in her room at night, a man and a woman. She tried confronting them one evening but they didn’t answer her and apparently just left. Amy became more convinced that there were other people living in her house, squatters of some kind. The problem was that although the stories Amy devised to explain what she insisted she saw sounded delusional there were no other indication that she was suffering from some form of dementia. Her memory and her reasoning remained as sharp as ever. Like a detective in one of Amy’s favourite whodunnits I was stumped. I couldn’t understand how she could have dementia without showing the more commonly described symptoms. The clue to solving the case came one evening I arrived for dinner.

After dinner, as Amy and I were talking she mentioned that she was having some problems with her eyes, something of an understatement I thought given the state of her vision. She asked if it was normal to see grid lines on the ceiling. As the conversation continued, she also mentioned that she sometimes saw other geometric patterns on the ceiling and walls. She knew that what she was seeing could not be real, but it puzzled her why she was seeing these things. Once I got home that night, I did a search of the internet and discovered that existence of Charles Bonnet Syndrome (C.B.S.).

C.B.S. is characterised by two main symptoms, the presence of hallucinations alongside the presence of progressive vision loss. It tends to be more common among the elderly, probably because a larger proportion of that age group suffer from progressive vision loss relative to younger age groups. Unlike the hallucinations that accompany neuropsychological disorders like dementia or psychoticism, those with C.B.S. are usually aware that what they are seeing is not real. The hallucinations seen vary in complexity. The patterns on walls and ceiling seen by Amy were of the least complex kind while the hallucinations of the cat and the people in her house were more complex examples of the C.B.S. hallucinations.

The currently accepted theory about why C.B.S. occurs is called deafferentation theory. This theory is based on the idea that processing visual stimuli from the external world inhibits the brain’s production of random, internally generated hallucinatory images. As there is less visual input to process with increasing vision loss, there is less inhibition of the random visual processing within the brain. It is this random visual processing that is thought to cause the hallucinations.The important point is that C.B.S. hallucinations are physiologically based, they are not the result of disorders in thinking like those often associated with the dementias.

Amy spent the last three years of her life in a rest home and then in a nursing home. As her vision continued deteriorating her hallucinations became more and more complex and it became more difficult for her to recognise that what she was seeing was not real. C.B.S. paired with feverish deliriums resulting from frequent urinary tract infections, meant that Amy’s world became increasingly separated from the world in which the rest of us lived. But it doesn’t need to be this way.

C.B.S. is a diagnosis of exclusion which means that it is only diagnosed after all other possible causes have been ruled out. The most recent estimation of the prevalence of C.B.S. is about 30% of the population suffering from some form of vision loss. No one knows for sure how many there are however. The fear of being thought ‘crazy’ understandably prevents many people, especially the elderly, from talking about the hallucinations to family or to their doctors. The hallucinations of C.B.S. are not normally frightening and for anyone whose vision is so bad that they cannot normally see, the clarity and variety of the hallucinations could be a pleasant alternative to the visual monotony associated with their vision loss. For this to happen however, C.B.S. needs to be recognised by both the public and the general medical establishment as a peculiar phenomenon associated with physiological vision loss. A 2018 Canadian study found that 74% of the family doctors surveyed were unaware or just slightly aware of the existence of the syndrome. This suggests that nearly three quarters of general practitioners would be unlikely to even consider the possibility of C.B.S. when faced with an older patient describing visual hallucinations, they would be more likely to reach the same conclusion we did with Amy, that the patient was showing signs of dementia.

The take home lesson? Should you or any member of your family start seeing fairies flying around your room or, more commonly, lines of ladies or gentleman in formal Victorian attire marching in front of you, don’t automatically assume that you are going crazy. If you know or suspect that your eyesight is worsening for any reason, at least consider the possibility that you are dealing with C.B.S. Think of it as your brain saying to you “Hey I know that your eyes are no longer working too well for you, so here is a gift from me to you. Sit back and enjoy the show.’