Definition

Charles Bonnet syndrome (CBS) is the occurrence of phantom visions in people living with some form of acquired vision loss* who are otherwise cognitively and psychologically healthy. These phantom images co-exist with one's usual visual experience (see Depictions).

 * disease/damage anywhere along the visual system from the eye to the visual regions of the brain.

 

Or put simply:

 

                     CBS is phantom images in sane, vision-impaired people.

 

Vision-impaired people who experience phantom images know that what they 'see' is not really there. Even so, they are often amazed at the startling detail of the imagery. These phantom images can include coloured blobs, geometric patterns, faces, figures, animals, flowers, buildings and even full landscapes.

 

Diagnostic criteria

Whilst there is no universally agreed upon set of diagnostic criteria for CBS, the core features seem to be:

  • Vision impairment (in eye or some part of the visual system)
  • Existence of phantom images
  • Full or near-full insight into the unreality of what one 'sees' (ie. no delusions)
  • No noticeable cognitive or memory issues
  • The visual images do not extend to other sense modalities (ie. no associated sounds, smells, taste or touch)

 

Peculiar

One of the quirkiest aspects of CBS images is that they can depict figures wearing clothing from a bygone era or incredibly elaborate costumes like for a fancy dress ball. This distinctive aspect of the condition continues to baffle researchers in the field.

 

The Condition:

  • was first noted by Charles Bonnet in 1760 in Geneva, Switzerland
  • was named after Charles Bonnet by a Swiss neurologist in 1936
  • reached the English speaking scientific community in the early 1980's
  • has been studied and published in diverse scientific journals over the past 35 years yet
  • remains today at the periphery of medical and health care interest.