Charles Bonnet Syndrome
Blindness, low vision, and seeing what is not there.
Posted October 29, 2024 | Reviewed by Margaret Foley
By the autumn of 2019, I had lost most of my vision. One day, I was sitting in my living room and saw two girls standing across the room. Although I heard nothing, the younger girl seemed to be talking excitedly to the older girl, who was smiling at me. I watched them for a few minutes until they disappeared. Another time, I was surrounded by a forest of bushes and small trees while walking toward the stairs. I saw that the forest continued up the stairs and onto the second floor.
From 2019 to 2021, I experienced visual hallucinations: I saw people, plants, and roomfuls of inanimate objects that did not exist. The hallucinations usually lasted a few minutes and occasionally occurred several times per day. I had developed a condition known as Charles Bonnet syndrome (CBS). The core feature of CBS is the presence of visual hallucinations in people with damage to their visual systems (Christoph et al., 2024; Pang, 2016). CBS develops only in people with acquired sight loss, not in those who have been blind since birth (Pelak, 2021).
Hallucinations are perceptions in the absence of sensory input (Lawn & Ffytche, 2021; Sacks, 2012). Put simply, when having visual hallucinations, people see things that are not really there. Visual hallucinations, in this sense, differ from imagined sights in that they are vivid, involuntary (they intrude upon consciousness), and uncontrollable (the images cannot be changed by an act of will). Although the visual hallucinations of CBS also occur in psychoses (American Psychiatric Association, 2022), CBS hallucinators do not show other characteristics of psychotic disorders or any other mental disorder.
Charles Bonnet (pronounced, Bah-nay ) was a natural philosopher who, in 1760, described the visual hallucinations experienced by his grandfather, Charles Lullin, who had lost most of his vision (Sacks, 2012). Bonnet described his grandfather as
a respectable man, full of health, … judgment and memory , who, in full alertness and independently of all impression from the outside, sees from time to time before him, faces of men and women, of birds, of coaches, of houses etc. (Bonnet, 1760, cited in Whitaker & Turgeon, 2007)
Georges De Morsier coined the term Charles Bonnet Syndrome in 1936 (Draaisma, 2009; Ffytche, 2007). He defined CBS as a condition characterized by visual hallucinations that occur in older adults. Interestingly, he believed that damage to the visual system was unrelated to the onset of visual hallucinations (Ffytche, 2007). However, since that time, most clinicians have agreed that sight loss is necessary for the development of CBS.
Today, most definitions of CBS include the following features (Jones et al., 2021; Pelak, 2021):
Estimates of the prevalence of CBS hallucinations in people with sight loss generally vary from about 15 percent to 40 percent, although some studies report estimates outside of this range (Christoph et al., 2024; Pang, 2016; Pelak, 2021).
What Causes CBS Hallucinations?
Our conscious visual experiences are primarily the result of activity in the visual areas of the cortex—the outer layers of the brain (Kolb & Whishaw, 2021). CBS hallucinations are the result of damage to the sensory pathways leading from the eyes to the visual cortex (Burke, 2002; Cox & Ffytche, 2014; Lawn & Ffytche, 2021).
This damage prevents external visual information from getting to the visual areas of the cortex. The decreased external activity triggers increased spontaneous activity of the visual areas. This activity underlies the production of “phantom” visual perceptions, which are hallucinated images related to the normal functioning of that area. For example, if spontaneous activity is generated in the face-perception areas, people will hallucinate faces (Jones et al., 2021).
When examining the decades of research on CBS, one is struck by the variability of some of the reported results. This variability is due to several factors.
First, many studies have small sample sizes (Christoph et al., 2024). Second, many studies do not use the psychiatric, toxicological, and neurological assessments needed to exclude participants with other conditions characterized by visual hallucinations (Christoph et al., 2024; Hamedani & Pelak, 2019; Pelak, 2021).
Third, different researchers have used somewhat different definitions of CBS (Christoph et al., 2024; Ffytche, 2007; Pang, 2016). For example, some researchers have defined CBS as a condition characterized by complex visual hallucinations. These researchers excluded people who experienced only simple visual hallucinations, such as floating dots, colors, shapes, and flashing lights. Other researchers, however, do include participants who experience only simple visual hallucinations (Pang, 2016; Pelak, 2021).
As well, many researchers define CBS as a condition in which participants know that what they are seeing is not real, which is called “insight.” However, many CBS hallucinators lack insight until after they have experienced several episodes (Pelak, 2021; Pang, 2016).
Psychological Consequences of CBS
The majority of people with CBS are either unbothered by their hallucinations or enjoy them (Jones et al., 2021). But about 30 percent react negatively to their hallucinations (Christoph et al., 2024; Cox & Ffytche, 2014). CBS hallucinators are most likely to react negatively when:
Clinical interest in therapeutic interventions has grown. Anecdotal reports sometimes support the use of drug treatments to decrease the frequency and duration of hallucinations (Pelak, 2021). And some observations suggest that hallucinators habituate over time to their disturbing hallucinations (Cox & Ffytche, 2014; Pang, 2016). Lastly, although hallucinations may persist for years, their duration and frequency may decrease over time.
For those who fear that they have a mental disorder, the best treatment is reassurance that their hallucinations are a normal reaction of the brain to a loss of sensory input. I am one of those CBS hallucinators who enjoyed their hallucinations while they lasted. Although they could make walking across my living room more difficult, I found them to be fascinating.
Acknowledgments: I thank Kiera Feng for her editorial assistance.
American Psychiatric Association. (2022). Schizophrenia spectrum and other psychotic disorders. In Diagnostic and statistical manual of mental disorders (5th ed., text rev.). American Psychiatric Association. https://doi.org/10.1176/appi.books.9780890425787.x02_schizophrenia_spectrum
Burke, W. (2002). The neural basis of Charles Bonnet hallucinations: a hypothesis. Journal of Neurology, Neurosurgery & Psychiatry , 73 (5), 535-541. https://doi.org/10.1136/jnnp.73.5.535
Christoph, S. E. G., Boden, K. T., Pütz, A., Januschowski, K., Siegel, R., Seitz, B., Szurman, P., & Schulz, A. (2024). Epidemiology and phenomenology of the Charles Bonnet syndrome in low-vision patients. International Ophthalmology , 44 (1), 1-11. https://doi.org/10.1007/s10792-024-03298-0
Cox, T. M., & Ffytche D. H. (2014). Negative outcome Charles Bonnet Syndrome. British Journal of Ophthalmology , 98 (9), 1236–1239. https://doi.org/10.1136/bjophthalmol-2014-304920
Draaisma, D. (2009). Disturbances of the mind (B. Fasting, Trans.). Cambridge University Press. (Original work published 2006).
Ffytche, D. H. (2007). Visual hallucinatory syndromes: Past, present, and future. Dialogues in Clinical Neuroscience , 9 (2), 173-189. https://doi.org/10.31887/DCNS.2007.9.2/dffytche
Hamedani, A. G., & Pelak, V. S. (2019). The Charles Bonnet syndrome: a Systematic Review of Diagnostic Criteria. Current Treatment Options in Neurology , 21 (9), 1-13. https://doi.org/10.1007/s11940-019-0582-1
Jones, L., Ditzel-Finn, L., Enoch, J., & Moosajee, M. (2021). An overview of psychological and social factors in Charles Bonnet syndrome. Therapeutic Advances in Ophthalmology , 13, 25158414211034715. https://doi.org/10.1177/25158414211034715
Kolb, B., & Whishaw, I. Q. (2021). Fundamentals of human neuropsychology (8th ed.). Worth Publishing.
Lawn, T. & Ffytche, D. (2021). Cerebellar correlates of visual hallucinations in Parkinson's disease and Charles Bonnet Syndrome. Cortex , 135 , 311-325. https://doi.org/10.1016/j.cortex.2020.10.024
Pang, L. (2016). Hallucinations Experienced by Visually Impaired: Charles Bonnet Syndrome. Optometry and Vision Science , 93 (12), 1466–1478. https://doi.org/10.1097/OPX.0000000000000959
Pelak, V. S. (2021). Visual Release Hallucinations (Charles Bonnet syndrome). UpToDate. Accessed October 1, 2021.
Sacks, O. (2012). Hallucinations . Knopf.
Whitaker, H. A., & Turgeon, Y. (2007). 13. Charles Bonnet’s Neurophilosophy. In H. A. Whitaker, C. U. M. Smith, & S. Finger (Eds.), Brain, mind and medicine: Essays in eighteenth-century neuroscience (Vol. 389, pp. 191-199). Springer. https://doi.org/10.1007/978-0-387-70967-3_14
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Jeffry Ricker, Ph.D., is a freelance health and science writer and disability advocate who lives in Scottsdale, Arizona.
This article is part of the Bringwise Psychology Journal — daily insights on human behavior, mental health, and personal growth.