Peer Reviewed

Case in Point

A Man’s Visual Hallucinations: Charles Bonnet Syndrome, Not Dementia With Psychosis

John Liantonio, MD, and Lauren Hersh, MD

John Liantonio, MD, and Lauren Hersh, MD

Liantonio J, Hersh L. A man’s visual hallucinations: Charles Bonnet syndrome, not dementia with psychosis. Consultant. 2017;57(7):422, 424.


Charles Bonnet syndrome (CBS) describes the clinical syndrome of visual hallucinations in cognitively intact but visually impaired patients.1 Low patient disclosure, a lack of awareness among health care providers, inadequate history taking, and inconsistent diagnostic criteria are key elements to its being underreported.2 The case described here illustrates how increased awareness and diligent history taking among health care providers can help uncover this often underdiagnosed and misdiagnosed geriatric syndrome.

Case Report

A 77-year-old man with a history of hypertension and bilateral cataracts presented for a geriatric falls assessment. A recent evaluation by his primary care provider for the onset of visual hallucinations had resulted in a diagnosis of dementia with psychosis. The patient described seeing strange figures, particularly in the morning. He had been started on a regimen of quetiapine, which had not resolved his hallucinations and had made him drowsy.

During the geriatric assessment, he was unable to complete a Montreal Cognitive Assessment (MoCA) screening tool due to his visual impairment. Based on our evaluation, including an in-depth and accurate history provided by the patient and normal results of a 3-item recall memory test, we did not believe he had dementia and were concerned about visual impairment causing the perceived cognitive dysfunction. We made a preliminary diagnosis of CBS.

Medication reconciliation revealed no iatrogenic causes for the patient’s symptoms. Results of laboratory blood tests and magnetic resonance imaging demonstrated no abnormalities. A consultant geriatric psychiatrist confirmed our diagnosis, and the patient was referred to the ophthalmology department for cataract removal, after which his vision improved and his hallucinations resolved.


CBS was named after the 18th century philosopher who described the visual hallucinations of his cognitively intact but visually impaired grandfather.1 The reported prevalence of CBS ranges from 0.4% to 14% among patients with low vision.2

While the etiology of CBS is poorly understood, the leading theory points to deafferentation of nerves somewhere along the visual pathway system as a precipitant for abnormal visual cortex function, leading to spontaneous neuronal discharge and hallucinations.2 Age-related macular degeneration and glaucoma are the 2 visual impairments most commonly associated with the development of CBS.

Risk factors (beyond the presence of an ocular lesion) include age, social isolation, low cognitive function, and a history of stroke.3 Clinically, CBS most frequently presents with complex hallucinations (brilliantly clear and detailed visuals, frequently featuring human forms and landscapes) in a patient who not only is cognitively intact but also is able to identify the hallucinations as a departure from reality.1,3

Traditionally, CBS had been viewed as a transient condition; however, hallucinations associated with CBS may in fact continue for years.4 While there are no formal diagnostic criteria, most clinicians agree on several core components: the presence of formed and complex hallucinations; full or partial retention of insight; absence of delusions; absence of hallucinations in other sensory modalities (eg, auditory or olfactory); and normal mental status.3

Timely and accurate diagnosis is confounded by this lack of formal criteria, by provider unawareness of the diagnosis, by patients’ reluctance to report hallucinations out of fear of a mental illness diagnosis, and by inadequate provider sensitivity and questioning techniques.3-6 Interestingly, reports of the occurrence of CBS in the ophthalmologic literature is quite scarce, and it is more frequently reported in neurologic, geriatric, and psychiatric journals.

There is no definitive cure for CBS, although various pharmacologic and behavioral interventions are utilized to varying degrees. Ultimately, correction of the underlying deficit or improvement of visual function with optical aids is the primary objective.7 Pharmacologic management includes the use of antipsychotic medications, venlafaxine, gabapentin, and carbamazepine, although their efficacy is largely based on anecdotal evidence and is frequently underwhelming.6,8-10 While the medical literature frequently depicts CBS as a rare and rather benign condition, more recent evidence has shed light on the fact that nearly one-third of affected patients report emotional distress, a decrease in functional capacity, and a decrease in quality of life.4

If a patient does not volunteer a history of a hallucinatory experience on a leading question, providers should ask a leading question along the following lines to elicit the presence of CBS: “It is well known that some people whose vision is blurred can sometimes see things that they know are not real. Have you experienced anything like this?”6

This case illustrates the need for increased awareness among health care providers about this common geriatric syndrome that can lead to diminished quality of life, increased functional impairment, and increased morbidity.4

John Liantonio, MD, is an assistant professor in the Department of Family and Community Medicine and an attending physician for the Palliative Care Service at Thomas Jefferson University Hospital in Philadelphia, Pennsylvania.

Lauren Hersh, MD, is an assistant professor in the Department of Family and Community Medicine at Thomas Jefferson University Hospital in Philadelphia, Pennsylvania.


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