Isa Mohamed Mohamud

Abstract

Charles Bonnet Syndrome (CBS) is a condition characterised by complex visual hallucinations in psychologically healthy individuals with significant visual impairment. This case report presents an elderly patient with bilateral age-related macular degeneration (AMD) who developed vivid visual hallucinations. The report discusses the presenting symptoms, investigations, differential diagnoses, pathophysiology, and management approaches for CBS. The aim is to raise awareness among clinicians to recognise and manage this frequently underreported condition effectively.

Introduction

Charles Bonnet Syndrome is characterised by the presence of complex visual hallucinations in cognitively intact individuals with significant visual loss. Although first described in 1760, it remains under-recognised, particularly among elderly patients with chronic ophthalmological conditions such as AMD, glaucoma, or diabetic retinopathy (1,2). These hallucinations are typically non-threatening, and insight is usually preserved, distinguishing CBS from psychiatric or neurodegenerative disorders (3).

Case Presentation

Patient Information

An 83-year-old female with bilateral geographic atrophy presents with a three-month history of visual hallucinations. She reports seeing vivid, life-like images of animals, children, and unfamiliar people inside her home. The hallucinations occur daily, last several minutes, and were seen in full colour.

Symptoms and Clinical Features

The hallucinations are purely visual, with no associated auditory, tactile, or olfactory components. The patient retains insight, acknowledging that the images are not real, stating: “I know they are not really there.” She denies any mood changes, delusional thinking, or memory issues.

She has a visual acuity of 6/60 in the right eye and 6/36 in the left eye. Dilated fundus examination shows well-demarcated areas of chorioretinal atrophy with loss of retinal pigment epithelium. Optical coherence tomography of the macular shows retinal thinning with loss of the outer retinal layers and disruption of the ellipsoid zone. Fundus autofluorescence reveals well-defined areas of hypoautoflurescence, consistent with RPE loss.

Past Medical History

• Hypertension (well-controlled)
• Mild Osteoarthritis
• No history of psychiatric illness, dementia, or substance use

Medication

Amlodipine 5 mg daily

Examination and Investigations

To exclude other organic or psychiatric causes of visual hallucinations, the following assessments were carried out:

Neurological Examination

MMSE score was 28/30, with no motor or sensory deficits. Gait and reflexes were normal.

Laboratory Tests

Full blood count, renal and liver profiles, thyroid function, and vitamin B12 levels were all within normal limits.

Neuroimaging

• CT Brain: No acute intracranial abnormality.

• MRI Brain: Age-appropriate cortical atrophy, with no signs of infarction, mass effect, or degenerative disease (3).

Ophthalmology

Fundus exam and OCT of the macula confirmed geographic atrophy consistent with bilateral dry AMD.

Diagnosis

The diagnosis of Charles Bonnet Syndrome was made based on the characteristic clinical triad:

1. Complex visual hallucinations
2. Preserved cognitive function and insight
3. Significant visual impairment (3).

Pathophysiology

The most widely accepted explanation for CBS is the deafferentation theory. Reduced visual input due to eye disease leads to disinhibition of the visual association cortex, which becomes hyperexcitable, analogous to phantom limb phenomena (4).

Functional MRI studies have shown that during hallucinations, there is abnormal activation in the ventral visual processing pathways, particularly in the occipital and temporal lobes (5). These internally generated images often appear vivid and detailed, reflecting preserved cortical processing of visual content.

Differential Diagnosis

Differentials considered included:

Dementia with Lewy Bodies (DLB): Typically associated with fluctuating cognition and Parkinsonian features, which were not present.

Delirium: No acute illness or altered consciousness was identified.

Primary Psychiatric Disorders (e.g. Schizophrenia): No delusions, auditory hallucinations, or loss of insight.

Occipital Lobe Epilepsy or Stroke: Excluded by neuroimaging and clinical presentation.

Substance-induced Hallucinosis: No history of substance use or medications known to cause hallucinations.

Management

CBS is often self-limiting. Management focuses on reassurance, education, and vision optimisation (6).

Patient Education

The patient was educated about CBS and reassured that it was a recognised condition related to her visual loss and not a sign of mental illness. This significantly reduced her anxiety.

Vision Optimisation

She was referred to a low-vision specialist. She was given magnifying aids, advice on high-contrast reading materials, and lighting improvements.

Behavioural Strategies

She was advised to change environments when hallucinations occurred, use distractions such as conversation or watching TV, and engage in activities to reduce occurrence.

Psychological Support

Although she declined formal counselling, her family was involved in supportive strategies. They were advised not to challenge the hallucinations but to validate her experiences and reduce isolation.

Pharmacological Intervention

No pharmacological treatment was needed initially as symptoms were non-distressing. If hallucinations become intrusive, low-dose SSRIs, antipsychotics such as quetiapine, or anticonvulsants may be considered (7,8).

Follow-Up and Outcome

At a three-month follow-up, the patient reported that hallucinations had decreased in frequency and were no longer distressing. Her insight remained intact, and no further intervention was required.

Discussion

CBS is a diagnosis of exclusion that affects 10–40% of visually impaired elderly individuals (9). Its underrecognition is likely due to patient reluctance to report symptoms for fear of being labelled as mentally ill, as well as lack of clinician awareness. CBS differs from psychiatric or neurodegenerative disorders in that patients retain insight and have no cognitive deficits. Neuroimaging is typically normal. Awareness of this syndrome allows clinicians to provide reassurance and avoid unnecessary tests or treatments. A multidisciplinary approach involving ophthalmologists, primary care, and mental health professionals is often beneficial.

Conclusion

This case illustrates the importance of recognising Charles Bonnet Syndrome in visually impaired elderly patients. Early diagnosis and appropriate reassurance can reduce distress and avoid misdiagnosis as psychiatric illness. Raising awareness among healthcare professionals is key to improving outcomes for patients experiencing CBS.

References

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