Health professionals' toolkit

When a patient or client reports visual hallucinations (phantom imagery) one can readily assume a psychiatric or neuro-degenerative aetiology. Charles Bonnet syndrome (CBS) is another plausible explanation that warrants consideration and is typically linked to some form of visual pathology (eg. macular degeneration, glaucoma, cataracts, diabetic retinopathy).

CBS is not associated with mental illness or cognitive decline. In fact, the CBS-affected person typically performs very well on a Mini-Mental Status Examination (MMSE). 


If a patient/client:

(a) Is known to have some form of eye disease / vision impairment 

(b) Presents with the symptom of repeated phantom imagery in their visual field

Then it may be advisable to ascertain whether they meet the following CBS criteria:


  1. Recurrent phantom images in the patient's visual field.
  2. Patient has insight into the unreality of what they 'see'.
  3. No evidence of cognitive or memory decline.
  4. Phantom images do not extend to other sense modalities. (no associated auditory, olfactory or tactile sensations)


If the patient is found to meet the above requirements and other conditions that could elicit phantom imagery have been ruled out (eg. delirium, dementia, Parkinson's, peduncular lesion, prescribed medication side-effects), then one could provisionally make a CBS diagnosis. 


To confirm a CBS diagnosis, a complete neurological or neuro-psychiatric work-up is recommended. 


Further notes:

  • The range of CBS phantom imagery is varied: from elementary forms such as dots, lines and geometric patterns through to more complex forms such as figures, faces, objects and even full landscapes. Images can be stationary or dynamic.  
  • Peculiar forms of imagery are often standard fare for CBS such as old-fashioned figures in elaborate headdress or distorted faces. 
  • Whilst ocular disease is believed to be the principal factor for CBS, there are instances of CBS developing due to a lesion (eg. infarct, brain tumour) along any part of the visual system pathway (ie. from the optic nerve to the occipital cortex).
  • Sensitive enquiry into the patient’s visual disturbances is strongly advised. Avoid the use of the term ‘visual hallucinations’ as it tends to invariably be associated with mental illness and will make the patient far more reluctant to disclose. Normalise the experience by mentioning that ‘many people with vision loss report seeing things that are not really there’.