Charles Bonnet Syndrome, Seeing Things That Are Not There After Sight Loss

A person whose sight has been getting worse sits in a quiet room and sees a row of tiny figures in hats walking across the wall. Or a pattern of grids and lattices that was not there a moment ago. Or a face with staring eyes. Those who have never heard of it can fear that something is wrong with their mind. It is in fact a recognised effect of sight loss, called Charles Bonnet syndrome, and this guide explains what it is, why it happens and what can help. The information comes from the Macular Society, a UK charity for people with macular disease.

What it is

The Macular Society describes Charles Bonnet syndrome as a condition that causes visual hallucinations as a result of sight loss. The condition is named after Charles Bonnet, the 18th century Swiss scientist and philosopher who first described it. It can be very common in people with macular disease.

A hallucination is the same experience as really seeing something, except that the something is not there. The hallucinations can come and go unannounced. They may last for only a few seconds, or they may stay for a day or more. The syndrome itself can last from days to many years, but for most people the hallucinations improve with time and only happen occasionally.

The charity makes one point first and repeats it. These hallucinations are not a sign of mental illness.

Why it happens

Researchers do not fully understand why Charles Bonnet syndrome happens in people with vision loss. They believe it may be because the brain does not receive enough visual information from the eye.

In a healthy eye, light reaches the photoreceptors in the retina, and these send visual information to the brain. The brain interprets that information to create a person’s vision. In people with macular disease, less visual information is sent, because the photoreceptors in the macula are not working. The charity explains that the brain may then start trying to fill in the gaps and create visual information for itself. That may be what causes the hallucinations.

Seen this way, the hallucinations are a response of the brain to missing signals, and not a sign of mental illness.

Who is most likely to have it

• Up to half of all people with macular degeneration are thought to experience it at some time.
• The hallucinations often start after a sudden worsening of vision.
• They are more likely if both eyes are affected by sight loss, but they can happen when only one eye has a problem.
• It does not only affect people with age-related macular degeneration. It can affect anyone with sight loss.

Sight loss has many causes. A guide to glaucoma, the sight loss you do not feel, and one on why a yearly retina check matters for people with diabetes describe two of them.

What people see

What a person sees is different from one person to the next. The charity lists a range.

• Simple, unformed flashes of light, colours or shapes.
• More elaborate forms, such as geometrical grids and lattices.
• Gardens, scenery or distant views, and animals.
• People, or processions of miniature figures in costume wearing hats.
• Faces with staring eyes, without a body.

Hallucinations of this kind are often seen in more vivid detail than real life. Some people find them amusing or interesting. For others they are distressing or frustrating, and they may be unsettling or frightening.

What treatment is available

The charity is frank about this. There are no treatments that stop the hallucinations happening completely, and none that remove the ones that appear. Research is trying to understand the cause better so that treatments can be found.

One study funded by the charity tested a form of non-invasive brain stimulation called transcranial direct current stimulation. It suggested that the therapy may help to reduce the number of hallucinations a person has, though more work is needed to confirm the results.

In rare cases, people with very distressing hallucinations may be offered medication. These medicines are usually prescribed for other conditions but have been shown to work for these hallucinations. A specialist doctor prescribes them, checks that they are safe to use and rules out other causes of hallucinations first.

Living with it

Hallucinations can be scary, and a person may worry about what they mean. The charity says that understanding what they are, and where they come from, can make them less scary. If a person feels scared or anxious, support is available, including talking to a counsellor.

It also helps to be well rested. Hallucinations can be worse when a person is stressed or tired, so good sleep at night is worth protecting.

Ways to stop a hallucination as it happens

There are a few suggestions for stopping a hallucination as it appears. They usually work by changing the visual information reaching the brain, or by interrupting the hallucination.

• Change the light, for instance by moving from a bright room to a dark one, or by switching the lights on or off.
• Close the eyes, look away from the image or walk into a different room.
• Try to touch the hallucination.
• Shine a torch upwards from below the chin, taking care never to shine it into the eyes.
• Try an eye movement exercise.

The eye movement exercise works like this. Imagine two points on the wall in front of you, about a metre apart, left and right. Stand about a metre and a half away. Look from one point to the other once every second, or faster, for 15 to 30 seconds. Do not move your head, and keep your eyes open. Rest for a few seconds. If the hallucination is still there, repeat the exercise. If it has not stopped after four or five attempts, the technique is unlikely to work, and you can try again another time or for a different hallucination.

How to tell whether something is a hallucination

There may be times when a person is not sure whether what they see is really there. The charity says that, typically, hallucinations of this kind are brighter or more vivid than the rest of the vision, or they follow the eye movement around the room. A person with the syndrome usually knows, at the time, that the image is not real. Not realising it is one of the signs listed in the next section that may point to another cause.

Driving

People sometimes ask whether they can still drive. The charity does not give a rule. Anyone who is concerned about driving with the syndrome should talk to a doctor or an eye specialist, who can advise.

When it may not be Charles Bonnet syndrome

Some features suggest that the cause may be something other than this syndrome. The charity lists the following.

• Hearing voices, or seeing and hearing things together.
• Seeing only people and animals, without patterns, colours, shapes and lines.
• Giving very detailed or elaborate explanations of what is seen or heard.
• Feeling the need to call the police or an ambulance.
• Not realising at the time that the hallucinations are not real.
• Confusion or memory difficulties.
• A companion noticing the hallucinations more clearly than the person who has them.

Anyone who notices these signs should contact a doctor or an eye specialist for advice.

What to tell the eye doctor

A short, clear account helps the doctor to decide whether the syndrome is the cause. It is worth saying the following.

• What you see, and how often it happens.
• How long each episode lasts.
• Whether the image moves with your eyes, or seems brighter than everything else.
• Whether your sight has recently got worse, since the hallucinations often start after a sudden worsening of vision.
• Whether anything else is happening, such as hearing voices, confusion or memory difficulties.
• What, if anything, makes the images stop.

Writing these points down before the appointment makes it easier to remember them, and a relative can come along to help.

If a relative tells you about it

The most useful thing to say to a relative is what the charity says first. The hallucinations are not a sign of mental illness, and they can be common in people with sight loss. Encourage the person to mention them to the eye doctor, who can check that nothing else is going on. If the person finds them upsetting, the doctor can advise.

More guides on conditions that affect sight are collected in the eye care and treatment section.

Where to ask

Anyone who has sight loss and has started to see things that are not there should say so at the next eye appointment. For general questions about visual hallucinations after sight loss, ask PEBS about Charles Bonnet syndrome. To give, visit the donate page.

Seeing things that are not there is a recognised effect of sight loss, and the first step is to tell the eye doctor.

This article is general information and does not replace an examination by an eye doctor.