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Hashemi Eye Care - Neuroscience Institute and Research Center

Charles Bonnet Syndrome

Visual hallucinations in people with vision loss, not a psychiatric condition but a brain response to reduced input.

3 min read

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.

Key Takeaways

  • Visual hallucinations in people with vision loss
  • Not a mental illness—normal brain response
  • Patients know hallucinations aren't real
  • Common but underreported due to fear of stigma
  • No specific treatment but reassurance helps
Simulation of a Charles Bonnet syndrome visual hallucination showing a faint translucent figure of a man standing in a living room as seen from the perspective of an elderly person sitting in a chair — illustrating how patients with vision loss may see vivid but unreal images that are not caused by psychiatric illness

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.

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