Charles Bonnet syndrome (CBS) is a disease in which visual hallucinations occur as a result of vision loss. CBS is not thought to be related to psychosis or dementia, and people with CBS are usually aware that their hallucinations are not real. While up to 38% of people with vision loss are estimated to experience hallucinations, the incidence may be higher due to underreporting, making CBS a widespread disease. In some cases, the hallucinations go away or become less frequent as the brain adapts to the loss of vision.

Symptoms of Charles Bonnet Syndrome

The primary symptoms of Charles Bonnet syndrome include significant vision loss (usually but not always), visual hallucinations, no control over the hallucinations, and a realization that the hallucinations are not real. Research suggests that many people with Charles Bonnet syndrome do not consult their doctors for fear of being diagnosed with a mental illness or disorder, such as dementia.

Understanding Charles Bonnet Syndrome


Causes of Charles Bonnet Syndrome

Even though researchers know vision loss triggers the hallucinations, the underlying reason behind Charles Bonnet syndrome is not thoroughly understood. One theory is that the loss of actual visual information from the eyes allows the brain to play with images in its stored picture library. CBS occurs most often among the elderly, who are more likely than any other age group to have eye conditions that affect sight, such as age-related macular degeneration.


Types of Hallucinations

Hallucinations associated with Charles Bonnet syndrome can be simple, non-formed images. This includes lines, light flashes, patterns, and geometric shapes. They also can be complex, such as images of people, animals, or scenes. They are generally not disturbing and do not involve other senses. Hallucination episodes can range from a few seconds to hours and may recur over the course of several days to years.


Timing and Frequency of Hallucinations

The timing and frequency, as well as the degree and complexity, of the hallucinations can vary widely. They tend to occur upon awakening and usually last only a few minutes. Typically, the timing and frequency have a distinctive pattern. However, no association has been found between the complexity of the hallucinations and the severity of vision loss.

Timing and Frequency of Hallucinations

Features of CBS Hallucinations

The features of hallucinations can vary widely from one episode to the next and from one person to the next. For example, the images may be color or black and white. They may appear static, like a photograph, or moving, like an event in real life, and they may be life-sized or reduced in size. In addition, the subject may be something realistic (animals from the real world) or fantastic (mythological monsters). The hallucinations may be brief (a few minutes) or lengthy (a few hours). People may see images that are enjoyable, like a pleasant dream, or frightening, like a nightmare. They may experience meaningless and random images or see familiar people or places, and the hallucinations may be different every time or may always contain the same things.

Features of CBS Hallucinations

Complications of CBS

People with Charles Bonnet syndrome have no control over their hallucinations. Although the hallucinations are not harmful, they may cause issues in everyday life because:

  • The hallucinations overlay images of the real world, so the person may have trouble negotiating daily tasks.
  • The person may not know at first whether the image is real or imagined. This can be frightening if they see, for example, a stranger in the house.
  • Seeing things that are not there is distressing, even if the images are pleasant.
  • The person may fear they are going insane or exhibiting signs of dementia.


Treatment for Charles Bonnet Syndrome

Currently, no single treatment is effective for all cases of CBS. However, certain steps have shown a positive effect, such as making regular visits to the ophthalmologist, wearing glasses or other aids to help maximize existing vision, and avoiding conditions known to aggravate CBS, such as stress, anxiety, social isolation, and sensory deprivation. In addition, people should understand that hallucinated images are benign and treatment is an option and take any doctor-prescribed medications for the condition.

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What to Do When Suffering a CBS Hallucination

The Royal National Institute of Blind People (RNIB) in the United Kingdom provides the following suggestions on how to deal with a CBS vision or hallucination:

  1. When a hallucination starts, hold your eyes open and look from left to right for 15 to 30 seconds without moving your head. If the hallucination continues, rest for a few seconds and try again for another 15 to 30 seconds.
  2. 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.
  3. Standing up or moving can stop the hallucinations, as can looking directly at the image, rolling your eyes, or blinking rapidly.

Understanding Charles Bonnet Syndrome


Other Causes of Visual Hallucinations

Visual hallucinations may have causes other than Charles Bonnet syndrome, including:

  • Dementia
  • Some forms of mental illness
  • Stroke
  • Estrogen replacement therapy
  • Parkinson’s disease
  • Psychotic drugs such
  • Blindness in one side of the visual field (hemianopia)
  • Pituitary tumor
  • Short-term aftereffects of cataract surgery
  • Migraine headaches
  • Brain tumors

Understanding Charles Bonnet Syndrome


The Discovery of CBS

The disease is named after Charles Bonnet, a Swiss naturalist and philosopher, who was the first person to describe the syndrome. In 1760, Bonnet described this syndrome and documented a range of complex visual hallucinations that occurred in psychologically sound people. He observed the symptoms in his 89-year-old grandfather who, though nearly blind from cataracts in both eyes, thought he saw men, women, birds, carriages, buildings, tapestries, physically impossible circumstances, patterns, and scaffolding.

Understanding Charles Bonnet Syndrome


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