Elsevier

Survey of Ophthalmology

Volume 48, Issue 1, January–February 2003, Pages 58-72
Survey of Ophthalmology

Major review
Complex Visual Hallucinations in the Visually Impaired: The Charles Bonnet Syndrome

https://doi.org/10.1016/S0039-6257(02)00414-9Get rights and content

Abstract

Visually impaired patients may experience complex visual hallucinations, a condition known as the Charles Bonnet Syndrome. Patients usually possess insight into the unreality of their visual experiences, which are commonly pleasant but may sometimes cause distress. The hallucinations consist of well-defined, organized, and clear images over which the subject has little control. It is believed that they represent release phenomena due to de-afferentation of the visual association areas of the cerebral cortex, leading to a form of phantom vision. Cognitive defects, social isolation, and sensory deprivation have also been implicated in the etiology of this condition. This condition, which is most common in the elderly, frequently goes unrecognized in clinical practice, due to both lack of awareness among doctors and patients' reluctance to admit to hallucinatory experiences, for fear of being labeled mentally unstable. Furthermore, patients who comprehend the unreality of their hallucinations may be distressed by the real fear of imminent insanity. Sensitive and sympathetic history taking is essential to ascertain the existence of hallucinations. Reassurance and explanation that the visions are benign and do not signify mental illness have a powerful therapeutic effect. Hallucinatory activity may terminate spontaneously, on improving visual function or on addressing social isolation. There is no universally effective drug treatment but anticonvulsants may play a limited role in aborting the hallucinations. Physician awareness and empathy are the cornerstones of management.

Section snippets

History

The eponym was coined by de Morsier,33, 34 recognizing the renowned Genoese naturalist, philosopher, and biologist Charles Bonnet (1720–1793), who in 1769 described the hallucinatory experiences of his grandfather Charles Lullin,18 in probably the first scientific documentation of a hallucinatory experience.32 Lullin, an intelligent and articulate 89-year-old magistrate, described subjective perception of silent visions of men, women, birds, carriages, and buildings, varying in size, shape, and

Definitions

Perception is the intuitive recognition of stimuli presented through the sense organs, while imagery is an experience within the mind, usually without the sense of reality that characterizes perception. Imagery so intense as to accord a photographic quality is referred to as eidetic. Eidetic imagery may persist, especially when looking at poorly structured backgrounds. This phenomenon, characterized by the simultaneous existence of real and unreal images (the subject being aware of the

Epidemiology

CBS occurs predominantly in elderly, visually impaired people.116, 144

Clinical Features

One of the earliest descriptions of the clinical features of CBS is that of Ernest Naville,103 who described his own visual hallucinations as intriguing, non-deceptive, non-distressing, exclusively visual experiences (without auditory accompaniment), occurring during clear consciousness and normal perception. He was unable to consciously control the appearance and disappearance of his visions; they vanished on closing his eyes.

Diagnostic Criteria

There is lack of consensus regarding the diagnostic significance of ocular pathology, neurological disease, and the cognitive state in the context of CBS.

Damas Mora et al described CBS as a condition in which “persistent or recurrent visual pseudo-hallucinatory phenomena of a pleasant or neutral nature occur in a clear state of consciousness. Despite vividness, clarity and impelling character, they are recognized as unreal. The condition tends to occur in the elderly with clinically preserved

Associated Conditions

Charles Bonnet hallucinations have been documented in association with a wide spectrum of pathology of the eyes and visual pathway, including age-related macular degeneration,50, 55, 70, 99, 101, 132, 156 cataract,12, 91 choroideremia,156 corneal opacities,31 glaucoma,31 retinal detachment,31, 132 enucleation,38, 88 multiple sclerosis with optic neuritis,25 retinitis pigmentosa,48 occipital infarction with both homonymous hemianopia37, 82 and bilateral loss of vision,135 venous congestion of

The Neuroanatomic Basis of Complex Visual Hallucinations

Foerster,47 studying the effects of faradic stimulation of various areas of the cerebral cortex, noted that stimulation of area 17 (the area striata) and area 18 resulted in subjective perception of elementary visual sensations/flashing lights, whereas that of area 19 (the visual association area) resulted in the subjective perception of complex formed visual sensations including figures, people, and animals. It has subsequently been suggested that complex hallucinations originate from activity

Theories of Pathogenesis

Bonnet himself suggested that these hallucinations have their origin in the part of the brain subserving visual function.18 In 1932 Jackson, conceptualizing the nervous system as a hierarchy of three levels, higher (cortical), middle (sub-cortical), and lower (brain-stem), postulated that higher centers exert a controlling influence on sub-cortical centers, loss of which allows the release of activity in disinhibited sub-cortical centers, resulting in hallucinations.138

Differential Diagnosis

The visually impaired are not immune to hallucinations secondary to other neuropsychiatric conditions or emotional disturbances;104 it is therefore important to exclude other possible causes of complex visual hallucinations, such as peduncular hallucinosis, Alzheimer's disease, delirium, Parkinsonism and levodopa-induced hallucinations, Lewy Body dementia, (recovery from) migraine coma, schizophrenia, medication, epilepsy, and hallucinations experienced during sleep–wake transitions.94, 136

Up

Management

Physician awareness and compassion are the mainstays of management for CBS. Though there is no universally effective therapy, treatment may not always be necessary, especially in cognitively intact patients,149 since visual hallucinations often cease spontaneously, in response to either improvement or further deterioration of visual function.150 Moreover, many patients with CBS are not distressed by the content of their hallucinations, as much as by anxiety about the significance of their

Discussion

There has been much controversy and disagreement about inclusion and exclusion criteria for CBS. Such criteria are arguably of limited relevance since they do not alter management in any way. In the pursuit of strict, well-defined criteria we perhaps overlook the clinical significance of this phenomenon—visual hallucinations can and do occur in patients with visual impairment. Such patients are often elderly and may be considerably distressed by their visions, the nature of which they do not

Conclusion

Eponymous labels are of limited value; however the term Charles Bonnet Syndrome may serve the essential function of reminding ophthalmologists that visual hallucinations can occur in the context of visual loss.29

Visual impairment is increasingly common in the elderly. Age-related macular degeneration, the leading cause of new irreversible blindness in the elderly,102 has been estimated to occur in 1 in 5 people over the age of 65 years.81 It is important that we recognize the occurrence of

Method of Literature Search

We undertook a Medline search using the following keywords: Charles Bonnet, visual hallucinations, pseudohallucinations and phantom visions. Relevant citations from the reference lists of selected articles were also reviewed. Inclusion or exclusion of any article in the text was based on relevance and the necessity to avoid redundancy.

Outline

I. History

II. Definitions

III. Epidemiology

A. Prevalence

B. Age distribution

C. Gender distribution

D. Under-recognition

IV. Clinical features

A. Content

B. Movement

C. Stereotypy

D. Triggering and relieving factors

E. Course

F. Hallucinations of other modalities

G. Patients' reaction to their hallucinations

H. Insight

I. The mental state

J. Fear of insanity

K. Visual function

L. Quality of life in visually impaired patients

M. Neurological features

N. Other risk factors

V. Diagnostic criteria

VI. Associated

Acknowledgements

The authors reported no proprietary or commercial interest in any product mentioned or concept discussed in this article. The authors wish to thank Volker Schloenvoigt, Vladimir Thaller, Jack Kanski, Astrid Moreno-Chamorro, and Alison Alexander for kind help with translation of French, German, and Polish articles. They also wish to express their gratitude to the library staff at the Derriford Hospital, Plymouth: Jeremy Smith, Samantha Brown, Abbie Cooper, Sarah Cohen, Sue Morris, Marilyn

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