Charles Bonnet Syndrome: Symptoms, Causes and Support

Charles Bonnet syndrome can cause visual hallucinations after sight loss. This guide explains assessment, possible support and the changes that require urgent medical attention. [1]

What Charles Bonnet syndrome means

Charles Bonnet syndrome, often shortened to CBS, describes visual hallucinations associated with sight loss. Someone may see geometric patterns, objects, people or animals that are not present. Images can be still or moving, coloured or monochrome, and brief or prolonged. The experiences are visual: sounds, smells or sensations of touch need consideration beyond the usual CBS description. These experiences do not automatically indicate dementia or a mental illness. This description cannot establish the cause of a new symptom in an individual. [1]

How the eyes and brain create vision

Seeing involves a chain of events rather than a picture travelling unchanged into the head. Light enters through the clear front of the eye, passes through the pupil and lens, and reaches the retina at the back. The retina contains specialised cells that convert light into electrical signals. Those signals travel through the optic nerve to the brain, which processes them into what a person sees. This explains why both eye health and brain function matter when investigating a visual symptom. A problem can affect incoming information, its transmission or its interpretation. The basic anatomy also helps distinguish the retina from the lens and the optic nerve: they perform different jobs, so conditions affecting them can produce different patterns of sight loss. An eye examination helps identify which structures and functions require attention. [11]

A leading explanation for CBS is that reduced visual input changes activity within the brain’s visual system. Researchers sometimes describe this as a release phenomenon: visual networks become active when the usual incoming information is reduced. This is an explanatory model, not evidence that a person is inventing the experience or choosing to imagine it. A recent study examined brain activity in people with eye disease, comparing those with CBS and a matched group without hallucinations. Its findings help investigate the model, but a research measure of brain activity is not a home test or a routine way for a reader to confirm CBS. The precise reasons one person develops hallucinations while another with apparently similar sight loss does not are still being investigated. An explanation can be useful while those scientific questions remain open. [34]

Insight can develop after the first experience

Insight means recognising that an image is not part of the external scene. Many people with CBS have this recognition, yet it may not be immediate when an unfamiliar image first appears. A small study of people attending a low-vision service found that some participants needed time to recognise the experiences as hallucinations. That observation supports a careful conversation about what happened initially and what the person understands now. It should not become a rule that any degree of uncertainty proves or excludes CBS. A clinician needs to hear about persistent changes in awareness, beliefs or thinking. Describe the experience without editing it to fit a definition. Someone can be distressed by a vivid image even after recognising that it is not real; understanding and emotional comfort are separate aspects of the experience. [14]

Who can experience it, and how long can it last?

CBS is associated with impaired sight and is often discussed in older adults because sight loss is common in that age group. It can also occur at other ages and with different degrees of visual impairment. A person does not need to describe themselves as completely blind before mentioning unusual visual experiences to an eye-care professional. The relevant starting point is what has changed in their vision and what they are seeing. Some people hesitate to speak because they expect disbelief or an unwelcome label. A calm explanation from a clinician and an opportunity to talk with trusted people can reduce that barrier. Ask about the experience in ordinary language and allow time for the answer. The person’s description is useful clinical information, even when it sounds unfamiliar to the listener. [6]

There is no reliable deadline by which CBS must disappear. Hallucinations may become less frequent, but some people experience them intermittently for years. They can recur after further sight loss, and a sudden increase warrants review for possible contributors such as an infection or a medicine. A familiar diagnosis should therefore remain part of the medical history rather than become an explanation for every later change. Review prescription medicines, eye drops, nonprescription products and supplements with the healthcare team. Do not stop prescribed treatment independently. The aim is to identify avoidable contributors while preserving treatment needed for other conditions. Monitoring should include how manageable the experiences are, not only whether they have stopped. [3]

Why the underlying eye condition still matters

Macular degeneration

Age-related macular degeneration affects the macula, the part of the retina involved in central vision. It can make reading, recognising faces and seeing fine detail difficult while other areas of vision remain useful. Understanding this pattern helps explain why a person may manage one activity and struggle with another. It also shows why a description such as poor eyesight is incomplete: the location and practical effect of the loss matter. Someone with macular disease should continue the assessment and treatment plan for that condition while discussing hallucinations separately. A change in central vision deserves attention on its own merits. Recognising CBS must not replace monitoring the eye condition that has affected sight. The questions for the eye team include what has changed, whether treatment is available and how to make everyday tasks more accessible. [18]

Glaucoma

Glaucoma involves damage to the optic nerve and often develops without obvious early symptoms. A person can lose areas of vision without immediately recognising the extent of the change. Treatment aims to slow further damage; it should not be described as a dependable way to restore vision already lost. This is why prescribed eye care and follow-up remain relevant even when hallucinations become the symptom attracting most attention. Bring concerns about administering drops, remembering treatment or understanding results to the eye-care team. A plan that is difficult to follow needs a practical review. Sudden severe eye symptoms are a different situation from gradual glaucoma and require urgent assessment. Do not assume that pain or a sudden deterioration is simply another part of an established visual hallucination condition. [19]

Cataracts

Cataracts make the lens cloudy, commonly causing gradually blurred or misty vision, difficulty seeing at night or problems with glare. Surgery replaces the cloudy lens with an artificial one and improves vision for most people, but the decision depends on the individual’s difficulties and eye health. Discussing a treatable cause of reduced sight is therefore part of a broader review. A clinician should explain what an operation is expected to improve and what uncertainties remain. Information about cataract surgery cannot, by itself, promise that CBS will disappear. Keep the intended visual benefit separate from any hoped-for change in hallucinations. This distinction helps people weigh the actual purpose of treatment without feeling that persistent images mean an otherwise successful eye procedure has failed. [17]

Diabetic retinopathy

Diabetic retinopathy affects blood vessels in the retina and may have no noticeable symptoms early on. Screening can identify changes before they become apparent in daily life. The screening programme and treatment plan address the risk of sight loss; they are not replaced by a discussion about CBS. People living with diabetes should tell their eye-care team about new visual changes and continue the monitoring recommended for them. Bring any difficulty reading appointment letters, using treatment equipment or managing eye drops into that conversation. Access barriers can affect follow-through even when someone understands why care matters. New floaters, blurred sight or deteriorating vision should be described directly rather than being given a familiar label in advance. The professional assessment determines what those changes mean. [20]

New flashes, floaters and shadows need their own assessment

Not every unusual visual effect is a CBS hallucination. Floaters may look like spots or threads, and flashes may appear as brief streaks of light. Some are harmless, but new or suddenly increased floaters or flashes, a dark curtain or shadow, blurred vision or eye pain need urgent eye assessment. A sight-threatening retinal problem must not be overlooked because a person already has sight loss or previously diagnosed CBS. Tell the service what appeared, when it started and whether vision changed at the same time. Do not wait for a routine review or test whether a distraction technique makes the symptom disappear. A response to changing lighting or looking elsewhere would not reliably exclude an eye emergency. The important action is to obtain the appropriate assessment promptly. [10]

How clinicians assess possible Charles Bonnet syndrome

There is no single test that confirms CBS. Clinicians assess the history and consider other explanations for hallucinations. They may ask about the images, their timing, the person’s sight and general health, and any changes in thinking or awareness. The examination and any further tests depend on what that assessment reveals. An internet symptom checklist cannot reproduce this process. It is reasonable to ask which possibilities are being considered and why a particular referral or test would help. Some people need support from more than one professional, especially when symptoms are distressing or the explanation is uncertain. A referral should be understood in terms of the question it is meant to answer, rather than treated as a diagnosis in itself. [7]

The eye examination contributes information about both vision and eye health. It can include reading a chart, checking the visual field and measuring eye pressure, with dilation allowing a closer look inside the eye. Different tests address different questions: how sharply someone sees is not identical to how much of the surrounding scene they can detect. Tell the examiner about practical changes as well as chart-reading difficulties. For example, locating objects, recognising faces or navigating unfamiliar spaces can matter even if the person still reads some print. Ask in advance whether drops will affect vision temporarily and what arrangements are needed after the appointment. These tests investigate the eyes; they do not independently explain every hallucination or replace the broader clinical history. Results should be interpreted together with that history. [29]

When new confusion or neurological symptoms change the urgency

A sudden change in attention, orientation or thinking is an emergency concern. Delirium can include hallucinations, but it may also make a person unusually disorientated or unable to follow a conversation. Infection, medicines, stroke and other illnesses are among its possible causes. Someone who suddenly becomes confused needs immediate medical help, even if they already have CBS or dementia. While help is being arranged, stay with them when possible, speak simply and offer calm reassurance. Avoid repeated questioning that adds distress, and gather their medicine information if this can be done without delaying care. The task is to recognise a significant change and obtain help, not to decide at home which condition caused it. An earlier explanation for visual images does not remove this need. [8]

Sudden facial drooping, weakness in an arm or difficulty speaking can signal a stroke. Other sudden neurological changes, including visual loss or severe problems with balance, also need urgent attention. Call the local emergency number rather than waiting for an eye appointment. In the UK, the emergency number is 999. Symptoms that improve or disappear still require emergency assessment. Do not drive yourself for emergency care. A previous CBS diagnosis cannot safely account for a new neurological deficit. Describe when the symptoms began or when the person was last known to be well, and follow the emergency service’s instructions. [4]

Dementia with Lewy bodies is one condition clinicians may consider when visual hallucinations occur alongside changes in cognition, fluctuating alertness, movement problems or disturbed sleep. These features require interpretation in context; a reader cannot diagnose or exclude the condition from a short list. Equally, seeing an image after sight loss does not automatically mean dementia. Both errors can be harmful: attaching a frightening diagnosis without assessment, or dismissing a broader change because CBS sounds reassuring. Family observations can help when they describe specific differences from the person’s usual functioning. Mention when a change began and what it affects. The clinician can decide whether neurological, memory or other specialist assessment is appropriate. The purpose of considering alternatives is a more accurate explanation and a suitable care plan. [9]

Hallucinations can also occur with medicines, infections, migraine, sleep-related experiences and several neurological or mental health conditions. Their cause is assessed using the wider picture. Report sounds, unusual smells, sensations of touch or changes in behaviour as well as visual images. New hallucinations merit urgent medical advice; the NHS directs UK readers to an urgent GP appointment or NHS 111. Rapid worsening, marked agitation, speech that no longer makes sense or immediate danger to anyone require emergency help. A clear description of the change is more useful than trying to decide which diagnostic label will be accepted. [2]

What treatment can realistically aim to do

Clinical guidance places education, reassurance, practical coping measures and appropriate referral at the centre of CBS care. Evidence for coping techniques is limited. Reassurance should follow assessment and explain the condition respectfully; it should not close down discussion of ongoing distress. Medicines have been reported to help in isolated cases, but that does not establish a routine treatment that is effective and safe for everyone. The 2026 guidance describes drug treatment and brain-stimulation approaches as experimental and in need of further evaluation. A specialist discussion may be appropriate for severe, persistent difficulties, with attention to possible benefits and adverse effects. There is no reason to copy a drug choice or device procedure from a case report. A care goal may be improved confidence, sleep or participation even while some images continue. Agree with the team which outcomes matter most. [13]

Trying coping strategies safely

People sometimes find that changing an activity, adjusting the lighting or redirecting attention changes an episode. Responses vary, so suggestions should be treated as options to discuss and try safely rather than a fixed programme. Choose an approach compatible with the person’s vision, balance and surroundings. For example, an audio activity can provide a different focus without requiring movement through an unfamiliar room. There is no requirement to stare at an image, touch it or repeat an exercise until it disappears. Stop anything that causes discomfort or makes the situation less safe. A brief note of what was happening and what seemed helpful can support a later discussion, but constant recording is unnecessary. A strategy that helps one episode may not help the next, and lack of benefit is not a failure of effort. [27]

Lighting is worth considering as part of everyday visual access. The useful change may involve where a lamp points, the shade, the position of a task light or the amount of light in a particular area. Brighter is not automatically better when it creates glare or discomfort. Think about the activity: finding a doorway, reading a label and sitting comfortably may need different arrangements. A low-vision professional can help assess those needs in the context of the eye condition. Introduce manageable adjustments and notice whether the space becomes easier to use. This is a practical accessibility step, not proof that lighting caused the hallucinations or a promise that changing it will stop them. Keep routes and frequently used objects predictable while making changes. [26]

Making the most of low-vision services

A low-vision assessment begins with the tasks that are difficult for the individual. It may explore how vision is being used, demonstrate magnifiers and other aids, and provide practice using them. Describe a real activity rather than asking only for the strongest device available. The distance between the eyes, the aid and the object can matter, and a tool that works for one task may be awkward for another. Ask for a demonstration that allows enough time to understand the method. If an aid is uncomfortable or remains unused, discuss the problem instead of assuming the assessment has exhausted the options. Contrast, lighting, audio and tactile information may all have a role. Local service arrangements differ, so ask the eye-care team how to obtain follow-up and practical training. [22]

Low vision can affect reading, recognising faces, distinguishing colours or using a screen. Its practical impact depends on the pattern of loss and the demands of the activity. Larger print, altered contrast, spoken output or a suitable magnifier can make some tasks more manageable. Start with a specific goal, such as reading a medicine label or following a favourite programme, and explain what currently gets in the way. An eye-care professional can help identify adaptations and check whether treatment for the underlying condition might protect or improve remaining sight. These steps address visual function. They should not be advertised as a proven cure for CBS, even when better access makes daily life less frustrating. Support is useful whether hallucinations are occasional, frequent or absent. [5]

Vision rehabilitation extends beyond selecting a magnifier. Depending on the person’s goals and local services, it can address daily living, accessible technology, mobility, employment and emotional adjustment. The starting conversation can be simple: which activities would you like to do more comfortably or independently? A rehabilitation professional can help break an activity into parts and identify where a skill, adaptation or different source of information would help. Someone may benefit from learning a new method even if the underlying vision cannot be restored. Ask how referrals work and whether support can be provided in a setting relevant to the difficulty. Rehabilitation and medical care serve complementary purposes. One supports participation and independence; the other evaluates and treats health conditions. Neither requires waiting until every hallucination has ended. [21]

Reading, technology and work

Reading aids vary in their purpose. A handheld magnifier may be convenient for a short label, while a stand magnifier can suit a longer task. Video magnifiers use a camera and screen and may offer adjustments to magnification, colour or contrast; some include speech. Those differences matter more than a general claim that one device is best for sight loss. Try the type of material that actually needs reading, including its size and layout, and ask for support learning the controls. Consider whether the tool can be positioned comfortably and used in the usual setting. A demonstration before purchase can expose practical difficulties that a product description will not. Choosing an aid belongs within an assessment of visual access, without promising that the device will change CBS itself. [23]

Computer access may combine larger text, screen magnification, altered colour settings and a screen reader. People can use both magnification and spoken information, changing the combination with the task. Training matters because unfamiliar controls can make a potentially helpful tool seem unusable. At work or during study, explain the barrier in concrete terms: locating a cursor, reading a dense page or following a shared screen may call for different adjustments. Agree how information will be supplied and who can help when a setting changes. The objective is reliable access to the task. It should not depend on the person continuously explaining private medical details to everyone involved. Choose support with the individual and review whether it works in practice. [24]

Emotional support is part of care

The effect of CBS cannot be measured only by counting images. A survey exploring emotional wellbeing found associations between a more negative experience of CBS, loneliness and negative emotional states. Because it was a cross-sectional study using self-reports, it cannot show which factor caused another or prove that social contact treats hallucinations. It does, however, underline why a clinical conversation should include how the person is feeling and functioning. Someone may be especially troubled by uncertainty, interrupted activities or fear of being misunderstood. Ask what is hardest rather than assuming the content of an image determines its impact. Support can then address the actual burden. A person who describes distress deserves help even if they have good insight and their experience seems manageable to someone else. [32]

Counselling can provide space to discuss the impact of sight loss, changes in identity, frustration and worries about daily life. Seeking that support does not, by itself, change the explanation for a visual hallucination or mean it arose from a mental illness. In the UK, RNIB offers sight-loss counselling and related emotional support, including options delivered remotely. Family and friends affected by sight loss may also be eligible for support. Check the service’s current arrangements and ask about communication needs when making contact. It is reasonable to say whether an individual conversation or a group feels more manageable. The purpose is to make support accessible and relevant, with room to discuss the person’s own priorities rather than expecting a particular emotional response to sight loss. [25]

The type of professional support should match the difficulty being addressed. A small study comparing an ophthalmology consultation with a psychiatric consultation did not establish an additional quality-of-life benefit from the psychiatric route for its participants. That finding cannot decide whether a particular person would benefit from psychological or psychiatric care. A small trial has limited ability to answer every question about distress, other symptoms or longer-term outcomes. Ask what a referral is intended to offer, such as further assessment or help managing anxiety, and how it connects with eye care. A helpful explanation reduces the chance that someone interprets the referral as an accusation or a dismissal. The individual remains entitled to an understandable reason for each part of their care. [31]

Talking with other people who understand

Peer groups can offer a place to discuss daily life with others who have sight loss or CBS. RNIB’s UK telephone groups include specialist CBS support, with facilitators helping people participate. Someone can ask about the format, accessibility and joining arrangements before deciding whether it suits them. Listening may be useful even when a person is not ready to describe their own experiences in detail. Other members’ accounts can help reduce isolation, but they cannot establish a diagnosis or determine whether a new symptom is safe to ignore. Keep medical questions with the relevant healthcare service. The value of a group can lie in being understood, sharing practical experiences and maintaining social contact, without making a claim that participation will stop hallucinations. [28]

Longer-term research also challenges the idea that successful support always means complete disappearance of the images. A survey of Macular Society members found that CBS could continue for years and that some respondents experienced a substantial negative effect on daily life. The participants were a selected group, so the findings are not a forecast for every person with sight loss. They support discussing both symptom persistence and its consequences. When reviewing care, ask whether an episode interrupts sleep, stops a chosen activity or changes confidence outside the home. An improved ability to respond calmly can matter even when frequency is unchanged. Conversely, continued symptoms that remain highly disruptive justify another conversation rather than being accepted as something the person must simply tolerate. [30]

Understanding what research can and cannot promise

Researchers are investigating treatments beyond the current supportive approach. A small placebo-controlled crossover trial of brain stimulation reported a reduction in hallucination frequency, but included only sixteen participants and called for larger studies. Measures of impact also improved during both active and placebo conditions. This illustrates why an encouraging research result is not the same as an established treatment recommendation. The size of the study, comparison group, outcomes and duration all affect what can reasonably be concluded. It does not justify buying a home stimulation device or copying an experimental procedure. A person interested in research can ask their clinical team about appropriately supervised studies and how participation differs from routine care. No result from this trial guarantees benefit to an individual. [15]

Education itself also needs careful evaluation. A small study compared two CBS podcasts and followed reported changes over a short period. It found no significant difference between the groups in behaviour change, although some participants described useful information or greater willingness to talk about symptoms. Without a group receiving no podcast, the study cannot establish every effect of listening. The practical lesson is to separate several possible benefits: understanding a condition, feeling more confident discussing it and reducing hallucinations are different outcomes. An accessible explanation may be worthwhile without being a treatment that eliminates symptoms. When reading a headline, ask what was actually measured and whether the conclusion matches that measure. Personal stories can be informative, but they should not be presented as proof that one technique works for everyone. [16]

Preparing for a useful appointment and follow-up

Before an appointment, identify the main questions and bring a brief description of the visual experiences. Include when they began, any accompanying changes and the activities most affected. A current list of medicines and supplements helps the clinician review possible contributors. Ask for information in a format that can be read or heard comfortably, and request an interpreter or other communication support when needed. During the discussion, clarify what is known, which questions remain open and why each proposed step is useful. Before leaving, check how results will arrive and whom to contact if symptoms change. The plan should distinguish routine follow-up from changes requiring urgent help. Preparing notes can make the conversation easier, but it must not delay assessment of a new urgent problem. [12]

A chosen relative, friend or carer can help prepare questions, take notes and remember the discussion. Agree that role beforehand so the appointment continues to centre the person receiving care. Supporters can describe observed changes without speaking over them or answering every question on their behalf. Ask permission before sharing personal information, and allow space for a private conversation with the clinician when wanted. Afterward, review the agreed next steps together, including practical help with transport, accessible paperwork or arranging another appointment. A supporter does not automatically become the decision-maker. Respecting the person’s preferences and privacy helps preserve trust, which can make it easier to raise a new symptom or admit that a coping suggestion has not helped. Good support remains collaborative as needs change. [33]

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