Charles Bonnet Syndrome


First noted in 1760, Charles Bonnet Syndrome (CBS, also known as phantom vision syndrome) describes the condition in which visual hallucinations are experienced by people of any age living with significant sight loss. It develops in some people, of any age, who have lost over 60% of vision. The vision loss can be due to eye disease, cancer, accident, stroke, diabetes or another condition which damages the optic nerve. Visual hallucinations are known as an event whereby a person can see an object or objects which are not actually there. The hallucinations it causes range from disturbing to terrifying but it is important to remember that CBS is not a mental health condition and there is nothing wrong with the mind. It happens because, as sight diminishes, the messages - which run all the time from the retina in the eye to the visual cortex in the brain - slow or stop. For some reason we have yet to discover, the brain does not stop. It fires up and creates its own images. What is seen depends on which part of the brain is firing at that moment. CBS is a reaction of the healthy brain, which fills in the gaps left by sight loss. For some people, they can be a strange, startling or frightening experience, but these events often become less frequent over time. Generally, you will be aware that what you are seeing in these hallucinations is not real.


There are two different categories of visual hallucinations that a person with CBS may experience, although in some cases a person may experience a range of both. The first category describes seeing simple repeated patterns or shapes. The second type of visual hallucination describes seeing complex visual hallucinations of people, objects or landscapes. These types of hallucinations may appear in colour or they may be black and white. These images may also move around. Each visual hallucination can last from between a few seconds to a few hours and may happen repeatedly over a number of days, weeks or years. While they can be an uncomfortable experience, some people become more accustomed to the hallucinations over time and may become more comfortable with them. For many, the hallucinations are thought to become less frequent with time.


The underlying mechanism by which this condition presents is unknown, although a number of theories exist. Research has suggested that a more significant loss of vision may correspond to an increased susceptibility to developing this condition.


If you start to see things around you which aren’t really there, this may be a sign of CBS. In this case, it is always good to meet with your eye doctor or GP who can help determine a diagnosis. While there isn’t one test to diagnose this condition, they can rule out other conditions with similar symptoms using various tests. By informing them of your medical history, your eye condition and describing the nature and frequency of your hallucinations will assist them in making a diagnosis.


At present, there isn’t a treatment for CBS which can stop these visual hallucinations from happening. Some people have found benefit from medications used to treat other indications, including epilepsy. However, such medications are powerful and can have serious side effects. It is important to speak with your doctor regarding a decision to try any of these treatments to see if they may be suitable for you. Where an eye condition can be managed, it may be possible to reduce the frequency of these events. By ensuring that a person’s vision is maximised, through wearing any prescribed lenses, using optical aids or through low vision rehabilitation, it can provide benefit in ensuring as much visual information as possible is transmitted to the brain for processing, leaving less need for the brain to fill in the gaps. It is also important to avoid any stressful situations and minimise anxiety, as this can aggravate CBS. Reassurance in knowing that these visual hallucinations are associated with CBS can provide comfort to people and help in coping with these events. Maintaining good eye health and having regular eye tests is also very important. Protecting your eyes as much as possible from further damage may help in trying to minimise the visual hallucinations you experience. No matter what level of vision a person may have, it is important to look after the eyes. To find out more about what can be done to take care of the eyes on a daily basis, please visit our Tips for Good Eye Health.


At present, many research groups are trying to confirm the underlying cause of this condition. In finding out more about the cause, it may reveal ways in which these hallucinations can be cured or treated. Research efforts are underway to identify how common the condition is. With increasing awareness of Charles Bonnet Syndrome, clinicians and researchers are discovering more about how it presents and why it appears in some individuals. Information about clinical trials can be found on their website and can be searched by condition and trial location. For further information, please contact the Research Department on 01 6789004.


Receiving a diagnosis can be overwhelming for anyone, but this is not a journey that you have to make alone. There are many groups and resources available to provide support for people living with Stargardt Disease. Fighting Blindness offers a free and confidential counselling service (Insight Counselling). For further information please contact or call 01 6746496. We also offer support groups for people with a visual impairment to share their feelings and experiences with others facing the same challenges. Please consult the support groups section of our website here to access the latest timings and days for the various support groups we offer. For further information please contact or call 01 6746496.


Esme's Umberella is a UK based charity working to raise awareness about CBS and funds for research. Féach provides support for parents of children living with sight loss in Ireland. NCBI (National Council for the Blind in Ireland) provides support and services for people living with sight loss in Ireland.   Last Updated: 18th February 2019