AKT · Ophthalmology/Neuro-ophthalmologylow yield

Charles Bonnet syndrome

Complex visual hallucinations in the visually impaired with intact insight

Overview

Vivid, complex visual hallucinations (people, animals, patterns) experienced by people with significant visual loss (e.g. AMD, glaucoma, diabetic retinopathy) who have INTACT insight and no psychiatric or cognitive disorder. It is a release phenomenon of the deprived visual cortex — benign and reassuring to recognise, not a psychosis.

Recognise

Recurrent complex, well-formed visual hallucinations (faces, figures, animals, patterns) in a person with poor vision
INSIGHT preserved — the person knows the images are not real; no delusions, no other-modality hallucinations
Common in elderly people with bilateral central visual loss (AMD); under-reported for fear of being thought 'mad'

Red flags

Auditory hallucinations, delusions, fluctuating cognition or other-modality features → reconsider psychiatric/neurological disease (Lewy body dementia, delirium)

Differentials & how to tell them apart

Lewy body dementiarecurrent visual hallucinations WITH cognitive fluctuation, parkinsonism and reduced insight

Deliriumacute, fluctuating, inattention, identifiable trigger

Psychosisdelusions and loss of insight; often auditory hallucinations

Occipital seizures/migrainebrief stereotyped simple phenomena

Investigations

Clinical diagnosis of exclusion: confirm visual impairment, intact insight, no psychiatric/cognitive disorder. Cognitive screen if doubt.

Management

Reassurance + explanation; optimise vision (no antipsychotic needed)

1Recognise and explain it: a benign release phenomenon of visual loss, NOT mental illness. Reassure, optimise the underlying eye disease and lighting, address isolation.Gate: Confirm insight is intact and there are no other-modality hallucinations/cognitive change before reassuring — Lewy body dementia and delirium are the mimics to exclude
2Persistent/distressing → low-vision and psychological support; medication rarely needed.

Usually none — reassurance and explanation are the mainstay

Optimise the eye disease / lighting — improving vision can reduce hallucinations

Key points

Complex visual hallucinations + poor vision + full insight = Charles Bonnet. The trap is mislabelling it psychosis or dementia; the patient knows the images are not real.

Monitor & prognosis

Reassess if cognitive/psychiatric features emerge.

Often improves over time; benign.

Source: RCOphth; cross-ref neurology (was an OFFMAP stray)