Charles Bonnet Syndrome: Symptoms, Types, Causes and Treatment

Charles Bonnet Syndrome (CBS) is a fascinating, often misunderstood condition where people with significant vision loss begin to experience vivid visual hallucinations. Despite the sometimes startling nature of these experiences, those affected usually maintain full insight, knowing that what they’re seeing isn’t real. As our population ages and conditions causing vision impairment become more common, understanding CBS is increasingly important for patients, families, and healthcare providers. In this article, we’ll explore the symptoms, types, causes, and treatments of Charles Bonnet Syndrome, drawing on the latest research to provide a comprehensive guide.

Symptoms of Charles Bonnet Syndrome

When people first experience Charles Bonnet Syndrome, it can be both confusing and distressing. Imagine suddenly seeing things that aren’t there—patterns, people, or objects—even though you know your mind is sharp. This is the reality for those with CBS. Let’s break down what these symptoms look like and how they typically present.

Symptom	Description	Frequency/Notes	Source(s)
Visual Hallucinations	Seeing things not present in reality	Formed (complex) or unformed (simple)	2 4 5 8 10 11
Insight Intact	Awareness that hallucinations are unreal	Maintained in typical CBS	2 7 8 9
No Psychiatric Illness	Absence of psychosis, dementia, or delirium	Cognitive function is preserved	2 3 7 8 9
Eye Closure Stops Hallucinations	Hallucinations disappear when eyes are closed	Common characteristic	3 8

Table 1: Key Symptoms

Visual Hallucinations: The Core Feature

The hallmark of CBS is the presence of visual hallucinations—images, shapes, or scenes that are not actually present. These can range from simple flashes of light or geometric patterns (simple hallucinations) to detailed images of people, animals, or objects (complex hallucinations) 2 4 5 8 10 11. These hallucinations can be vivid and detailed, sometimes even colorful, and may appear static or moving 8.

Preservation of Insight

A defining feature of CBS is that those affected usually understand that their hallucinations are not real. This insight is critical in distinguishing CBS from psychiatric conditions like schizophrenia or dementia, where the person may believe the hallucinations are real 2 7 8 9.

Absence of Other Psychiatric Symptoms

People with typical CBS do not experience hallucinations in other senses (like hearing voices) and do not show other signs of mental illness or cognitive decline. Their intellectual functioning remains intact 2 3 7 8 9.

Triggers and Patterns

Hallucinations in CBS often occur when the person is in a low-stimulation environment, such as a dimly lit room or when their eyes are closed, and typically cease when the eyes are shut 3 8. Episodes can last from seconds to hours and may recur frequently.

Emotional Reactions

The emotional response to these hallucinations varies. Some find them distressing or frightening, while others are indifferent or occasionally amused 7 8. Fear or anxiety may arise, especially if the person is unaware that these symptoms are benign 8.

Types of Charles Bonnet Syndrome

CBS is not a one-size-fits-all condition. Its presentation can vary, and researchers have begun to classify different types based on symptoms and associated features. Understanding these types can help clinicians tailor support and management strategies.

Type	Key Features	Associated Factors	Source(s)
Typical CBS	Visual hallucinations, full insight, no psychiatric comorbidity	Visual loss, preserved cognition	2 7 8 9
Atypical CBS	Reduced/lost insight, cognitive decline, other sensory hallucinations	Psychiatric comorbidity, dementia	7
Simple Type	Unformed hallucinations (lights, shapes)	Often in severe vision loss	5 8
Complex Type	Formed hallucinations (people, animals, objects)	May persist longer, more detailed	5 8 10

Table 2: CBS Types Overview

Typical Charles Bonnet Syndrome

This is the classic presentation: individuals with significant visual loss develop visual hallucinations but retain full awareness that what they see isn’t real. No other sensory hallucinations or psychiatric symptoms are present 2 7 8 9.

Atypical (CBS Plus)

Atypical or "CBS plus" refers to cases where additional features are present, such as reduced insight, mild cognitive impairment, or hallucinations in other sensory modalities. This variant may overlap with psychiatric or neurologic conditions, such as dementia or depression 7. Patients may also have a history of psychiatric illness or develop significant emotional distress in response to their hallucinations.

Simple vs. Complex Hallucinations

CBS can also be divided based on the nature of hallucinations:

• Simple (Unformed) Hallucinations: These include flashes, geometric shapes, or patterns. They are more common in those with profound vision loss 5 8.
• Complex (Formed) Hallucinations: These are detailed and may include images of people, animals, or intricate scenes. Such hallucinations may be more distressing or last longer 5 8 10.

Variable Experiences

The hallucinations can be static or moving, monochrome or colorful, and may appear anywhere in the visual field. Some patients experience persistent hallucinations in specific areas, such as the central vision, especially when other visual input is lacking 8.

Causes of Charles Bonnet Syndrome

CBS arises from a complex interplay of factors, most notably visual system impairment. Let’s delve into what leads to its development.

Cause	Mechanism/Association	Notes/Examples	Source(s)
Visual Pathway Damage	Deprivation/disruption of visual input	AMD, glaucoma, cataract	2 8 10 11
Neurologic Disorders	Lesions in visual cortex or pathways	Stroke, vascular issues	6 12
Social Isolation	Possible contributing factor	More common in isolated	3
Aging	Increased risk with age	Higher prevalence in elderly	4 5 10 11

Table 3: Causes and Risk Factors

Visual System Impairment

The most common cause of CBS is significant loss of vision due to eye diseases. Conditions like age-related macular degeneration (AMD), glaucoma, diabetic retinopathy, cataract, and rare genetic disorders like Leber’s Hereditary Optic Neuropathy disrupt the flow of visual information to the brain 2 8 10 11. This deprivation is thought to trigger spontaneous activity in the visual association cortex, leading to hallucinations 8.

Neurologic and Vascular Factors

While CBS is primarily linked to eye diseases, it can also result from brain lesions affecting the visual cortex or its connections. Strokes, especially those impacting the posterior cerebral or vertebrobasilar arteries, can cause deafferentation and similar symptoms 6 12. Sometimes, cerebral pathologies (such as tumors or trauma) that interrupt the visual pathway may also trigger CBS 11 12.

Social and Psychological Contributors

Social isolation and lack of stimulation have been observed as potential contributing factors. People who spend more time alone or in low-stimulation environments may be more likely to develop CBS symptoms, possibly due to the brain compensating for sensory deprivation 3.

Age as a Major Risk Factor

CBS is significantly more common in older populations, correlating with the increased incidence of visual impairment in this age group 4 5 10 11. However, it can occur in younger individuals with severe vision loss 8.

Not a Psychiatric Disorder

Crucially, CBS is not a sign of mental illness or dementia, though atypical cases may overlap with these conditions 7. Most affected individuals are mentally healthy aside from their visual impairment.

Treatment of Charles Bonnet Syndrome

Living with CBS can be challenging, but several approaches can help alleviate symptoms and improve quality of life. Here’s what research says about treatment and management.

Treatment Approach	Description/Strategy	Evidence/Notes	Source(s)
Reassurance	Explaining benign nature of CBS	Reduces anxiety, improves coping	8 10 13
Vision Improvement	Correcting underlying eye disease	May resolve/reduce hallucinations	10 13
Low Vision Rehab	Visual aids, occupational therapy	Supports adaptation, function	11 13
Pharmacotherapy	Medications (anticonvulsants, neuroleptics)	Mixed results, for severe cases	14 15

Table 4: Treatment Strategies

Patient Education and Reassurance

For most patients, understanding that CBS is a common, benign response to vision loss is the most effective intervention. Education and reassurance can greatly reduce fear and distress, especially if hallucinations are frightening or misunderstood 8 10 13. Patients often feel relieved once they know their experiences are not a sign of insanity or impending dementia.

Treating Underlying Eye Conditions

Improving vision when possible—through cataract surgery, better diabetic control, or other means—can sometimes eliminate or reduce hallucinations 10 13. However, in some cases, the damage is irreversible.

Low Vision Rehabilitation

Occupational therapy, visual aids, and environmental adaptations can help patients make the most of their remaining sight and adjust to vision loss. These interventions may not stop hallucinations entirely but can improve overall wellbeing and function 11 13.

Pharmacological Approaches

Medications are generally reserved for severe, persistent, or distressing cases. Studies report variable success with anticonvulsants (like valproate or carbamazepine) and some atypical neuroleptics (like melperone) 14 15. Traditional antipsychotics, antidepressants, and benzodiazepines have shown limited effectiveness 15. Treatment decisions should be individualized and made in consultation with clinicians experienced in CBS and its comorbidities.

Addressing Psychiatric Comorbidities

Those with atypical CBS or significant emotional distress may benefit from psychiatric evaluation and support 7. Managing depression, anxiety, or cognitive impairment can improve quality of life and reduce hallucination-related distress.

Conclusion

Charles Bonnet Syndrome is a unique and often misunderstood condition at the intersection of eye health, neurology, and psychiatry. As vision loss becomes more prevalent in our aging society, awareness and understanding of CBS are vital. Here’s what we’ve covered:

• CBS is characterized by visual hallucinations in people with vision loss, with preserved insight and cognitive function in typical cases.
• Types of CBS include typical (with intact insight) and atypical (with psychiatric or cognitive features), as well as simple and complex forms based on hallucination content.
• The primary cause is loss of visual input, usually from eye diseases, but neurologic factors and social isolation can contribute.
• Treatment focuses on reassurance, vision rehabilitation, and addressing underlying visual or psychiatric issues, with medication reserved for select cases.

By fostering understanding and open communication, patients and caregivers can better navigate the challenges of CBS, ensuring that those affected maintain dignity, confidence, and quality of life.