Charles Bonnet syndrome

Overview

Charles Bonnet Syndrome (CBS) is a condition in which individuals with significant vision loss experience visual hallucinations, despite having no underlying psychiatric or cognitive disorder. These hallucinations are purely visual—people with CBS are fully aware that what they see isn't real, and there are no hallucinations involving hearing, smell, or touch. First described by Swiss philosopher Charles Bonnet in 1760, the syndrome is more common in elderly individuals with vision impairments, especially those caused by conditions like macular degeneration or glaucoma.

Causes

The exact cause of Charles Bonnet Syndrome is not completely understood, but it is believed to result from the brain's response to vision loss. When visual input is reduced or absent due to eye disease, the visual cortex in the brain may become hyperactive and generate its own images. Known triggers and associated conditions include:

• Age-related macular degeneration (AMD): The most common cause

• Glaucoma

• Diabetic retinopathy

• Cataracts or retinal detachment

• Stroke or damage to the visual pathway (rare)

Risk increases with the degree of vision loss, but not all visually impaired individuals will develop CBS.

Symptoms

Individuals with Charles Bonnet Syndrome experience complex visual hallucinations that vary in frequency, duration, and detail. Common characteristics include:

• Visual hallucinations: Often vivid, colorful, and detailed, such as faces, people, animals, patterns, or landscapes

• Recurrent episodes: Hallucinations may occur sporadically or frequently, often when the person is in a quiet or dim environment

• No awareness impairment: The person knows the images are not real

• No other sensory involvement: Hallucinations are purely visual—no voices or sounds

• No underlying psychiatric illness: Mental health remains otherwise intact

Diagnosis

Charles Bonnet Syndrome is diagnosed clinically, often after ruling out other causes of visual hallucinations. Diagnostic steps include:

• Medical history and symptom description: Including onset, type of hallucinations, and insight into their unreality

• Ophthalmologic evaluation: To assess the extent of visual impairment

• Neurological and psychiatric assessment: To rule out conditions like dementia, delirium, or schizophrenia

• Brain imaging (e.g., MRI or CT scan): In some cases, to rule out stroke or brain lesions

Many cases go unreported due to fear of being labeled mentally ill, so clinician awareness is essential for diagnosis.

Treatment

There is no specific cure for Charles Bonnet Syndrome, but several strategies can help reduce hallucinations or make them more manageable:

• Reassurance and education: Explaining the condition often alleviates fear and anxiety

• Visual stimulation: Keeping the eyes and brain active (e.g., with TV, reading, or social interaction) can help

• Lighting and movement: Bright lighting and eye movement may reduce the intensity of hallucinations

• Correcting vision: Using glasses, magnifiers, or surgery (e.g., for cataracts) to optimize any remaining vision

• Medications: Rarely used, but antipsychotics or anticonvulsants may be prescribed in severe cases

• Psychological support: Counseling or support groups can help individuals cope with distress caused by hallucinations

Prognosis

The prognosis for Charles Bonnet Syndrome is generally favorable. Hallucinations may lessen over time or disappear altogether, especially if vision improves. Most individuals adapt well once they understand the benign nature of the condition. However, for some, persistent hallucinations can be distressing and affect quality of life. Regular follow-up and reassurance are key. Increasing awareness among healthcare providers and patients is essential to ensure timely diagnosis and support.