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The Charles Bonnet syndrome (CBS: Charles Bonnet Syndrome) is a condition characterised by visual hallucinations that occur in people with ocular deficits, but who are not affected by psychiatric conditions or cognitive disorders.

CBS is a rather common condition that is very often misdiagnosed and is still not fully understood, either by doctors or patients.

New Guidelines

A group of researchers from King's College London published in January 2026 in Nature new guidelines for identifying and managing CBS in the clinical routine of ophthalmological laboratories.

This interdisciplinary protocol was developed by hallucination experts and researchers with the aim of integrating clinical evidence with real-world expertise to reduce the impact that Charles Bonnet syndrome can have.

Visual hallucinations

Hallucinatory experiences may include the vision of simple shapes, but also complex images of people, animals or landscapes.

In the case of Charles Bonnet syndrome, the hallucinations are purely visual, while the cognitive capacity remains intact. Indeed, in the presence of other sensory manifestations or loss of cognitive capacity, the presence or coexistence of psychiatric or cognitive pathologies should be considered.

The correct patient history should include the onset, frequency, duration and context in which the hallucinations occur.

Possible triggering mechanisms include glare, fatigue and stress.

In terms of differential diagnosis, it must be considered that the perception of flashes of light or zigzag lines can constitute 'theichopsia', i.e. a temporary visual deficit that can last up to 20 minutes with a subsequent return to normal vision. A curtain-like shadow could, on the other hand, be the first symptom of a retinal detachment, i.e. an ocular emergency requiring immediate intervention.

Frequency

The authors of the study pointed out that Charles Bonnet syndrome can occur in the presence of a wide range of eye diseases associated with visual loss.

Epidemiological studies estimate that CBS may affect one in five patients among those attending low vision centres for conditions leading to progressive vision loss.

Sometimes hallucinations can be induced or exacerbated by certain classes of drugs, including the proton pump inhibitorsoften prescribed for gastrointestinal problems, and the psychotropic agents with predominantly antimuscarinic effects, administered to treat certain neurological disorders.

Drugs with an impact on vascular function, including nitrates, calcium channel blockers, ACE inhibitors, triptans and sympathomimetic drugs, may alter retinal or cerebral blood flow and be associated with scintillation, halo effects, flashes of light.

In such cases, medical therapy should be reviewed with the general practitioner or specialist following the patient to decide on an adjustment of the dosage or replacement with an appropriate alternative.

Mechanism of onset

The mechanism of onset of visual hallucinations appears to be based on 'release' or 'de-afferentation', in which reduced visual input leads to increased excitability of the visual cortex.

It is important to emphasise that the risk of hallucinations increases in proportion to diseases resulting in more severe visual loss, but CBS can also occur when visual acuity is relatively preserved.

Patient approach

A key clinical aspect is that many CBS patients tend not to spontaneously reveal that they suffer from hallucinations, except when confronted with specific questions, often out of fear of being judged mentally unstable.

To overcome this reluctance, the researchers propose using a clear and reassuring approach, with questions such as 'Some people with similar eye conditions occasionally see things that are not really there. Has anything similar ever happened to you?".

If the patient reports suffering from visual hallucinations, the guidelines suggest exploring the details: time of onset, frequency, duration, trigger mechanisms, and emotional impact of these visual disturbances.

Qualitative approaches

A number of validated assessment instruments for the characterisation of CBS, such as the North-East Visual Hallucination Interview (NEVHI) and the Questionnaire de Repérage du Syndrome de Charles Bonnet (QRSCB), have also been developed, but these may be difficult to administer in settings with many patients and tight operating times, as is often the case in many ophthalmic laboratories.

Patient management

L'patient education constitutes a true therapeutic intervention because once reassured that CBS is a non-psychiatric condition, approximately 70% of patients report a marked reduction in stress related to these visual symptoms.

For those who remain under stress, the authors of the guidelines suggest cognitive-behavioural and environmental strategies to reduce the intensity and frequency of CBS symptoms: blink or distraction techniques, eye gymnastics, improved ambient light and relaxation methods such as meditation or breathing exercises.

In the case of a persistent negative impact of CBS, when hallucinations are accompanied by a negative impact on the quality of life with states of anxiety, fear or depression, it is recommended that the patient be referred to forms of psychiatric or neurological support.

These patients may have to deal with difficulties due to hallucinatory symptoms that may lead to an increased risk of reduced work activity and social relationships.

Psychological support from specialised clinicians following the diagnosis of Charles Bonnet syndrome can be instrumental in reducing stigma and improving the patient's psychological condition.

The following may also be considered pharmacological interventionswhich have shown beneficial effects in some case reports. Medications that could be administered include antiepileptics, antipsychotics, antidepressants and acetylcholinesterase inhibitors.

There are also reports on the potential benefit of neuromodulation techniques such as direct transcranial stimulation. However, these latter approaches are still experimental and require further evaluation before being introduced into routine clinical practice.

• Jones, L., ffytche, D.H. & Moosajee, M. Management of Charles Bonnet syndrome in routine eye care services. Eye (2026). https://doi.org/10.1038/s41433-025-04215-0
• Christoph SE, Boden KT, Siegel R, Seitz B, Szurman P, Schulz A. The prevalence of Charles-Bonnet syndrome in ophthalmic patients: a systematic review and meta-analysis. Brain Res Bull. 2025;223:111282.
• bySilva Morgan K, Collerton D, Firbank MJ, Schumacher J, ffytche DH, Taylor JP. Visual cortical activity in Charles Bonnet syndrome: testing the deafferentation hypothesis. J Neurol. 2025;272:199.