New Research from Canada: Approximately One in Five Persons with Vision Loss Experience Visual Hallucinations

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Charles Bonnet (“Bo-NAY”) Syndrome (CBS) is a condition that causes vivid, complex, recurrent visual hallucinations, usually in older adults with later-life vision loss from eye conditions that can include macular degeneration, diabetic retinopathy, and glaucoma.

The visual hallucinations associated with CBS can range from animated, colorful, dreamlike images to less complicated visions of people, animals, vehicles, houses, and other everyday items. It has long been difficult, however, to determine the actual numbers of adults with vision loss who are affected by CBS, since few people who experience these hallucinations are likely to discuss them with family members, friends, or physicians.

Now, a new Canadian study indicates that visual hallucinations are experienced by approximately 1 in 5 persons with vision loss caused by any eye disease, warranting greater awareness of the phenomenon among all vision health professionals and their clients, consumers, and patients.

The Canadian Journal of Ophthalmology

The new Charles Bonnet Syndrome study, entitled Prevalence of visual hallucinations in a national low vision client population, has been published online as an open source article in the February 2016 edition of the Canadian Journal of Ophthalmology, authored by Keith D. Gordon, Ph.D., from the Canadian National Institute for the Blind (CNIB), Toronto, Ontario.

The Canadian Journal of Ophthalmology is the official journal of the Canadian Ophthalmological Society and is committed to timely publication of original, peer-reviewed ophthalmology and vision science articles.

About Charles Bonnet Syndrome

Who Was Charles Bonnet?

engraving of Charles Bonnet in profile

Charles Bonnet (March 13, 1720 – May 20, 1793) was a Swiss naturalist and philosopher and the first person to describe the syndrome.

Initially, he observed symptoms of the syndrome in his 87-year-old grandfather, who was nearly blind from cataracts, yet still “saw” men, women, birds, carriages, buildings, scaffolding, and tapestries before his eyes.

In 1760, Bonnet described his eponymous syndrome, in which he documented a range of complex visual hallucinations that occurred in seemingly psychologically intact persons.

What Is Charles Bonnet Syndrome?

Charles Bonnet Syndrome (CBS) was first introduced into the English-speaking psychiatric literature in 1982. Lighthouse Guild International provides helpful illustrations and a definition of CBS, including an important distinction between CBS visions/illusions and delusions:

[Individuals] who perceive these visions know they’re … mirages, of sorts. That is, the images are illusions, not delusions. The difference is that a person with delusions is convinced that what s/he sees is real. [People] with Charles Bonnet Syndrome may initially second-guess themselves, but ultimately accept that their perceptions have no substance.

In other words, adults with CBS are usually in good mental health and come to understand that these illusions or “hallucinations” are not sensate or “real.” In addition, the illusions associated with CBS are usually solely visual and do not occur in conjunction with the other senses (hearing, smell, taste, or touch).

What Causes Charles Bonnet Syndrome?

CBS is sometimes referred to as “phantom vision” syndrome, and can be compared to “phantom limb” syndrome, in which an individual can continue to receive sensation – and even pain signals – from a limb that has been amputated.

Similarly, in CBS, when retinal cells no longer receive and relay visual images to the brain, due to eye disease or damage to the optic pathways, the visual system begins creating its own “phantom” images. You can find more information at Charles Bonnet Syndrome: Why Am I Having These Visual Hallucinations? on the VisionAware website.

More about the Charles Bonnet Syndrome Study

From Largest study of its kind shows 1 in 5 people with vision loss caused by eye disease experience visual hallucinations, via Canadian Newswire:

A new study conducted by CNIB has found that one in five Canadians with vision loss who were surveyed experience visual hallucinations, known as Charles Bonnet Syndrome (CBS). It represents … the first major study of CBS due to vision loss across of the three most common eye diseases – age-related macular generation, diabetic retinopathy and glaucoma – with 2,565 study respondents over 40 years of age who attended a CNIB low vision clinic.

“Many doctors believe that this phenomenon is very rare; however, this study shows that it’s actually quite prevalent,” said Dr. Keith Gordon, study author and Vice-President of Research at CNIB. “People are afraid to tell their family, friends, and even doctors that they’re experiencing hallucinations for fear of it being misunderstood as mental illness. With these findings, we are now able to shed more light on CBS and help raise awareness within the medical community and the general public about how prevalent it actually is.”

Widely considered quite rare among the medical community, the study shows that in fact CBS is a common condition among people with serious vision loss, characterized by temporary visual hallucinations. CBS is not a mental illness, nor is it a symptom of dementia or any other disease. Rather, it is a condition specifically related to vision loss.

Lack of awareness of this condition can cause confusion and concern among those experiencing and diagnosing it. While it is not yet known exactly what causes CBS, researchers are beginning to believe it is related to an attempt by the brain to fill in information that would normally be obtained from the eyes.

CBS hallucinations only affect sight, not hearing, smell or touch. The hallucinations may seem “real” (like seeing cows in a field when the field is actually empty) or “surreal” (like seeing dragons). Most frequently, people will see patterns or simple shapes; however, there are many accounts of more complex hallucinations, such as the following examples:

  • Little men holding umbrellas at the end of the bed
  • Women in red dresses sweeping the floor
  • Cloakroom tickets lining the walls and ceiling
  • Soldiers marching down the street

The CNIB study also showed:

  • There was no higher probability of hallucinations between any of the three major eye diseases (age-related macular degeneration, diabetic retinopathy, and glaucoma).
  • Respondents who experienced greater levels of vision loss had higher chances of experiencing hallucinations.
  • Although vision loss occurs more frequently in older people, the risk of developing CBS does not increase as people age.

More from the Canadian Journal of Ophthalmology

From the article abstract:

Participants: 2,565 new clients older than 40 years attending a Canadian National Institute for the Blind (CNIB) vision rehabilitation clinic.

Methods: Participants were asked the following question: “Many people who come to CNIB tell us that they see things they know are not there. Some see patterns or shapes. Others see images of people or animals. Have you ever experienced this?” Responses were cross-tabulated on the basis of age, sex, eye disease, visual acuity, and whether the clients lived alone.

Results: Overall, 18.8% of people surveyed indicated that they had experienced hallucinations. Females showed higher odds of hallucinations than males did. Clients with greater vision loss had higher chances of experiencing hallucinations than those with the lowest level of vision loss. There was no significant difference in the chances of experiencing hallucinations between people with age-related macular degeneration, diabetic retinopathy, and glaucoma, or in older versus younger respondents. People who did not live alone had higher chances of experiencing hallucinations than those who lived alone.

Conclusions: Visual hallucinations are experienced by approximately 1 in 5 patients with vision loss caused by any eye disease, warranting greater awareness of the phenomenon among all vision health professionals and their patients.

Additionally, the study addressed the following limitations and conclusions:

  • Although this study evaluated the relationship between CBS and visual acuity/visual fields, it did not assess contrast sensitivity, a factor known to correlate with the odds of having visual hallucinations.
  • Although the terms “visual hallucinations” and “CBS” have been used interchangeably, there is a possibility that some of the CBS hallucinations may in fact be because of causes other than vision loss. No attempt was made to confirm the diagnosis of CBS.

Studies of CBS depend on the ability to overcome the subjects’ reluctance to disclose that they are experiencing hallucinations because they might think that this would label them as mentally ill. In spite of the careful wording of our question, it is possible that some reluctance remained, and as a result the true prevalence of CBS may be higher. This reluctance and different attitudes toward mental illness may also account for the reported differences in prevalence among studies conducted in different societies.

All post–vision loss rehabilitation therapists need to be prepared to advise their clients that hallucinations are often associated with losing one’s vision so that they understand that the experience is not atypical. People need to feel reassured that they are not suffering from mental health disorders.

At the same time, however, all health professionals need to refer patients experiencing hallucinations to family doctors, neurologists, psychiatrists, or other specialists to rule out other conditions that may be causing the hallucinations or to help patients if what they are experiencing is not because of CBS. Furthermore, these physicians need to consider CBS when seeing a patient with vision loss who is reporting visual hallucinations.

VisionAware will provide updates of Charles Bonnet Syndrome research as they become available

Charles Bonnet Syndrome: When the Eyes Play Tricks

Mary D'Apice head shot

In When the Eyes Play Tricks: Charles Bonnet Syndrome Explains Visual Hallucinations in Those With Visual Impairments, journalist and VisionAware Peer Advisor Mary D’Apice (pictured at right) interviews Dr. Susan Hirshfield, a clinical psychologist and Living Skills Specialist at the Earle Baum Center of the Blind in Santa Rosa, California, who integrates a discussion of Charles Bonnet Syndrome into all of her agency’s services.

Twelve years ago, Dr. Hirshfield was unfamiliar with the syndrome, but as a clinical psychologist, she had an intuitive understanding that some visual hallucinations were not necessarily a sign of mental illness or dementia. Read more about Dr. Hirshfield and learn about ways that her clients Martha, Dolores, and Cindy learned to deal with their Charles Bonnet visions.

Dr. Hirshfield also tells the story of Ann, who would walk into her living room and find it full of strangers. She had Ann make a large sign in bold, black ink that read “Touch them.” She instructed Ann to tape the signs to her bedroom door, her refrigerator, her bathroom mirror, and all over the house. “Once she could reach out and had tactile connection with the fact that there wasn’t anything there,” Dr. Hirshfield said, “the image went away. Eventually Ann was able to comfort herself knowing that only she and her dog were in the house.”

Learn more about the many ways that VisionAware can help you or your family member:

Additional Information

Charles Bonnet image source: Wikimedia Commons. This image is in the public domain because its copyright has expired.