Charles Bonnet Syndrome

Charles Bonnet syndrome (CBS) is a condition where people with significant vision loss experience vivid visual hallucinations. It's not a psychiatric disorder—it's the brain "filling in" visual information when input from the eyes is reduced.

What People See

• Faces (often distorted or unfamiliar)
• People, animals
• Geometric patterns
• Buildings, landscapes
• Colors, lights
• Images may be detailed and vivid
• Can be pleasant, neutral, or disturbing

Characteristics

• Patient knows hallucinations aren't real (insight preserved)
• Only visual—no sounds, smells, etc.
• Can last seconds to hours
• May occur daily or occasionally
• Often worse in dim light or when tired
• No other psychiatric symptoms

Who Gets CBS

• People with significant vision loss
• Any cause of vision loss can trigger it
• More common in elderly
• Macular degeneration most common underlying cause
• 10-40% of visually impaired people affected
• Many don't report it, fearing psychiatric diagnosis

Why It Happens

• "Deafferentation" theory
• Brain visual areas continue to work but get less input
• Brain generates its own images to fill void
• Similar to phantom limb phenomenon

Diagnosis

• Clinical history
• Preserved insight (knows not real)
• Visual hallucinations only
• Confirmed vision loss
• No psychiatric disorder
• Normal mental status otherwise

Management

• Reassurance—most important, not a mental illness
• Explain the mechanism
• Improve lighting
• Increase visual stimulation
• Treat underlying vision loss if possible
• Medications rarely needed

Prognosis

May decrease over time as brain adapts. Some have persistent symptoms. Quality of life generally preserved with understanding.