Charles Bonnet Syndrome

Many people may be surprised to find this listed as a common eye condition but it has been reported to affect between one in two people to one in five people with visual loss. Charles Bonnet was a naturalist who in the late 1760s described the visual hallucinations experienced by his grandfather.  It can affect cognitively healthy people, often the elderly. It does not affect people who are born with visual impairment. It is believed to be unreported by many patients who are concerned that they may be misdiagnosed with dementia or other cognitive conditions.

Signs/Symptoms:

  • Visual hallucinations which can be patterns or lines but can be as vivid as seeing people, objects or even buildings
  • Significant visual loss
  • Age is a risk factor
  • Patient realises that the hallucinations are not real, however, this does not make them less frightening or distressing
  • Associated with vision loss due to diabetic eye disease, age related macular degeneration, cataracts or glaucoma for example
  • Only affects sight – there are no associated auditory or olfactory hallucinations.

Causes:

  • The brain’s adaption to significant visual loss – the exact causation is not fully understood but is believed to be associated with the brain creating images (hallucinations) to replace the visual information that is no longer coming from the eyes.

Treatment:

  • Usually resolves after 12-18 months
  • Counselling or low vision rehabilitation therapy may help
  • Dispensing of low visual aids
  • Adjustments to lighting levels
  • Reduce tiredness and stress

Red Flags:

Charles Bonnet syndrome can be linked to serious health problems such as strokes or macula disease so patients should be referred according to local protocols.

Red Flags: When one or more of these red flags is raised, a conversation with another registrant in practice should take place following which appropriate referral or management should be actioned and noted. If there are no other registrants in practice then contact should be made with colleagues elsewhere or contact should be made for advice to the local Hospital Eye Service.