What is Charles Bonnet Syndrome?

Charles Bonnet Syndrome: Diagnosis and Management

Charles Bonnet Syndrome (CBS) is characterized by recurrent, vivid visual hallucinations in individuals with vision loss who maintain insight that their hallucinations are not real, without evidence of cognitive impairment or other neurological/psychiatric disorders explaining the hallucinations. 1

Epidemiology and Clinical Features

• Prevalence ranges from 15% to 60% among patients with ophthalmologic disorders, depending on the population studied 1
• Most commonly affects elderly individuals with age-related macular degeneration or other causes of vision loss 2
• Key diagnostic features include:
  • Complex, well-defined visual hallucinations
  • Preserved insight (patients recognize hallucinations aren't real)
  • Visual impairment/vision loss
  • Absence of cognitive impairment
  • No other neurological or psychiatric explanation for hallucinations 1

Hallucination Characteristics

• Often described as "Lilliputian hallucinations" (objects appear smaller than normal) 2
• Typically well-defined, organized, and clear images over which the patient has little control 2
• Usually non-threatening and may include faces, geometric figures, animals, or other complex imagery 3
• Hallucinations typically lack personal meaning for 77% of patients 4
• More likely to occur during periods of sensory deprivation or low arousal 4

Pathophysiology

• Believed to represent a "release phenomenon" due to deafferentiation of visual association areas in the cerebral cortex 2
• Similar to "phantom vision" phenomenon
• Cognitive defects, social isolation, and sensory deprivation have also been implicated 2
• Higher incidence in patients with massive loss of peripheral visual field 2

Management Approach

1. Patient Education and Reassurance (First-line approach)

   • Explain that CBS is common in visually impaired people
   • Emphasize that CBS is not a psychiatric disorder or sign of cognitive decline
   • Reassurance alone provides significant relief for many patients 1

2. Vision Optimization

   • Maximize remaining vision through vision rehabilitation services
   • Improve lighting conditions (task lamps, pocket flashlights)
   • Reduce glare with tinted eyeglasses or visors
   • Increase contrast in the environment (using black felt-tipped pens, contrasting colors) 1

3. Behavioral Techniques

   • Teach specific eye movements when hallucinations occur
   • Implement distraction techniques
   • Engage in social activities to reduce isolation 1

4. Psychological Support

   • Recommend support groups for patients with vision loss
   • Monitor for comorbid depression or anxiety, which may require separate treatment 1

5. Emerging Treatments

   • Transcranial Direct-Current Stimulation (tDCS) shows potential in reducing hallucination frequency 1
   • Selective serotonin reuptake inhibitors may be effective in some cases (limited evidence) 3

Prognosis and Follow-up

• Approximately 60% of patients experience improvement or resolution of hallucinations within 18 months 1
• Regular follow-up is recommended to:
  • Assess hallucination frequency and impact on quality of life
  • Monitor for atypical features suggesting other diagnoses
  • Screen for development of depression or anxiety 1

Important Clinical Considerations

• CBS is frequently underdiagnosed - only 1 of 16 patients who consulted doctors received the correct diagnosis in one study 4
• All patients benefit from reassurance that their hallucinations do not imply mental illness 4
• Watch for atypical features that suggest diagnoses other than CBS:
  • Lack of insight
  • Interactive hallucinations
  • Hallucinations in other sensory modalities
  • Progressive cognitive decline 1
• In rare cases, CBS may overlap with psychiatric disorders, complicating diagnosis and management 5