Editor’s note: One of the many benefits associated with an online information center and website, such as VisionAware, is the ability to track readers’ search terms [i.e., information readers are seeking as they search the Internet]. Since the earliest days of VisionAware.org, and more so during the past year, the following questions appear consistently within our top searches:
- I’m seeing things that I know aren’t there. What is wrong with me?
- I’m nervous because I see people in my house, but I know they’re not really there. Why is this happening?
An Answer from VisionAware
Many vision professionals believe that a significant number of adults with vision loss from a variety of eye conditions, including macular degeneration, diabetic retinopathy, and glaucoma, experience Charles Bonnet (“Bo-NAY”) Syndrome, a condition that causes vivid, complex, recurring visual hallucinations, usually (but not only) in older adults with later-life vision loss.
By some estimates, as many as 20-30% of adults with vision loss are affected by CBS, although actual numbers are difficult to determine, since few people who experience these symptoms are likely to discuss them with family members, friends, or physicians.
To better understand this reluctance, it’s helpful to learn the basics about Charles Bonnet Syndrome (CBS), including its causes, symptoms, and experimental treatments and therapies that have shown promise in treating CBS.
Who Was Charles Bonnet?
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 people.
What Is Charles Bonnet Syndrome?
Charles Bonnet Syndrome (CBS) is a condition that causes vivid, complex, recurring visual hallucinations, usually (but not only) in older adults with later-life vision loss. It was introduced into the English-speaking psychiatric literature in 1982.
The “visual hallucinations” associated with CBS can range from animated, colorful, dreamlike images to less complex visions of people, animals, vehicles, houses, and similar everyday images.
Lighthouse International (now Lighthouse Guild) provides a helpful definition of CBS “visions,” 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 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 (such as this image of a blue moose reflected in the window at left).
In a National Public Radio story about CBS, ophthalmologist Jonathan Trobe, M.D., from the University of Michigan, explained it this way:
“The brain is a mash-up of stored visual memories. When visual cells in the brain stop getting information, which happens when your rods and cones stop working, the cells compensate. If there’s no data coming in, they ‘make up’ images. The cause of this disorder is thought to be a misfire in the brain similar to the neurological mix-up that occurs in patients with phantom limb syndrome. As vision wanes, the brain continues to interpret visual imagery in the absence of corresponding visual input, just as it sometimes continues to process pain signals from a limb that’s no longer there.”
More Interventions for Charles Bonnet Syndrome
Charles Bonnet Syndrome is a “diagnosis of exclusion,” which means that the diagnosis can be made if there is no other neurological diagnosis to explain the hallucinations. If there are additional neurological problems or symptoms such as memory loss, weakness, or tremor, a patient should be referred to a neurologist to rule out other conditions (such as stroke, Parkinson’s disease, psychological disorders, or dementias) that could be contributing to the hallucinations.
The Royal National Institute of Blind People (RNIB) in the United Kingdom provides a number of helpful suggestions to help with CBS visions and hallucinations:
Sometimes just standing up or moving slightly can help to get rid of the hallucinations. Some people also find that looking directly at the image they are seeing causes it to fade. Sometimes moving your eyes or blinking rapidly can also help.
When a hallucination starts, look from left to right, about once every second for 15 to 30 seconds, without moving your head. Your eyes should be held open during the movements. If the hallucination continues, have a rest for a few seconds and try another 15 to 30 seconds of looking left and right.
If the hallucinations have not diminished or stopped after four or five periods of looking left and right for 15 to 30 seconds, the exercise is unlikely to work and you can stop. It may be worth trying again on another occasion or for a different type of hallucination.
The level of lighting may influence your hallucinations. If your hallucinations happen in dim light, try opening the curtains or turn on a light or the television, as the change in lighting may help to stop the hallucinations. If your CBS happens when there’s a lot of light, then switching off a light may also help.
After a year or perhaps 18 months, the brain seems to adjust to the person’s vision loss, and the hallucinations begin to recede. CBS-related hallucinations are more likely to occur when the person is awake, alone, and in dim light, or when he or she is physically inactive or lacks distractions, such as television.
A CBS Study from the United Kingdom
Although generally it is thought that CBS hallucinations start to recede in approximately 12-18 months after the brain adjusts to the individual’s vision loss, a 2014 study from the United Kingdom has shed new light on CBS, indicating that CBS hallucinations may last far longer (five years or more) and have more serious psychological consequences than previously acknowledged.
From Better education needed on sight loss hallucinations at The Macular Society:
The research, published online by the British Journal of Ophthalmology, documented the experiences of 492 visually impaired people who had experienced visual hallucinations. They suggest there is a serious discrepancy between medical opinion and the realities of the condition.
The phenomenon, known as Charles Bonnet Syndrome, is widely considered by the medical profession to be benign and short-lived. However, the research shows that 80% of respondents had hallucinations for five years or more and 32% found them predominantly unpleasant, distressing and negative.
The study described this group of people as having “negative outcome Charles Bonnet Syndrome.” The group was more likely to have frequent, fear-inducing, longer-duration hallucinations, which affected daily activities. They were more likely to attribute hallucinations to serious mental illness and were less likely to have been warned about the possibility of hallucinations before they started.
Of respondents, 38% regarded their hallucinations as startling, terrifying, or frightening when they first occurred and 46% said hallucinations had an effect on their ability to complete daily tasks [and] 36% of people who discussed the issue with a medical professional said the professional was “unsure or did not know” about the diagnosis.
Dr. Dominic ffytche, clinical senior lecturer at King’s College London’s Institute of Psychiatry who led the research said, “With no specific treatments for Charles Bonnet Syndrome, the survey highlights the importance of raising awareness to reduce the distress it causes, particularly before symptoms start. All people with Charles Bonnet Syndrome are relieved or reassured to find out about the cause of their hallucinations and our evidence shows the knowledge may help reduce negative outcome.”