Health professionals' toolkit
If a patient/client:
- Is known to have some form of eye disease / vision impairment
- 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:
Recurrent phantom images in the patient’s visual field. (ie. visual pseudo-hallucinations)
- Patient has insight into the unreality of what they ‘see’. (ie. no delusional thinking or behaviour)
- No evidence of cognitive or memory decline.
- Phantom images do not extend to other sense modalities. (eg. 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, 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.
- 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 full landscapes. Images can be stationary or dynamic.
- Peculiar forms of imagery are often standard fare for CBS such as old-fashioned figures in 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’.