Eyes - Charles Bonnet syndrome

Charles Bonnet syndrome refers to the visual hallucinations caused by the brain’s adjustment to significant vision loss. It occurs most often among the elderly who are more likely than any other age group to have eye conditions that affect sight, such as age-related macular degeneration.

Estimates vary, but it is thought that about one person in every two with vision loss may experience hallucinations, which means Charles Bonnet syndrome is very common. Despite this, most people are not aware of this condition.

Research suggests that many people who suffer from Charles Bonnet syndrome do not consult their doctor out of fear and embarrassment, as hallucinations are associated with mental illness. In most cases, the hallucinations go away as the brain adapts.

Causes of Charles Bonnet syndrome

The underlying mechanism of Charles Bonnet syndrome is not understood. Doctors know that vision loss triggers the visual hallucinations. It is not clear how the brain stores visual information, but we know that visual information from the eyes stops the brain from creating its own images. Perhaps the loss of visual information from the eyes allows the brain to ‘play’ with its stored picture library.

Symptoms of Charles Bonnet syndrome

The signs and symptoms of Charles Bonnet syndrome include:

• Significant vision loss
• Visual hallucinations
• No control over the hallucinations
• A realisation that the hallucinations aren’t real.

Types of hallucinations in Charles Bonnet syndrome

Generally, the hallucinations tend to occur when the person is alone, quiet and in a familiar environment, for example, when lying awake in bed.

The two types of visual hallucination most common to Charles Bonnet syndrome include:

• Simple – such as patterns and lines, for example, the person may see brickwork images, netting or mosaics
• Complicated – such as seeing people, buildings, landscapes or places. Complicated hallucinations are more likely to occur in people with severe vision loss.

Features of Charles Bonnet hallucinations

The features of hallucinations can vary widely from one episode to the next and from one person to the next. For example, the images may be:

• colour, or black and white
• static like a photograph, or moving like an event in real life
• life-sized, or reduced in size
• realistic (such as animals from the real world), or fantastic (such as mythological monsters)
• brief (they continue for a few minutes), or lengthy (they persist for a few hours)
• enjoyable like a pleasant dream, or frightening like a nightmare
• meaningless and random, or featuring familiar people or familiar places
• different every time, or a person may see the same items in every hallucination.

Complications of Charles Bonnet syndrome

A person with Charles Bonnet syndrome has no control over their hallucinations. They may cause issues in their everyday life because:

• The hallucinations overlay images of the real world, so the person may have trouble negotiating everyday tasks, such as walking through an unfamiliar environment.
• The person may not know at first whether the image is real or imagined, which can be frightening if they are seeing, for example, a stranger in the house.
• Seeing things that aren’t there is distressing, even if the images are pleasant.
• The person may fear they are going mad or exhibiting signs of dementia.

Other causes of visual hallucinations

Visual hallucinations may have causes other than Charles Bonnet syndrome, including:

• dementia
• some forms of mental illness
• stroke
• oestrogen replacement therapy
• parkinson’s disease
• psychotic drugs such as cannabis
• blindness in one side of the visual field (hemianopia)
• pituitary tumour
• short-term after-effects of cataract surgery
• kidney dialysis that includes the hormone erythropoietin.

Diagnosis of Charles Bonnet syndrome

Diagnosis of Charles Bonnet syndrome may include:

• your medical history
• a physical examination
• an eye examination
• medical tests to rule out other causes of visual hallucinations.

Treatment for Charles Bonnet syndrome

In most cases, Charles Bonnet syndrome resolves itself after about 12 to 18 months without treatment. It is a good idea to find out everything you can about Charles Bonnet syndrome. Understanding the condition can help to reduce feelings of anxiety and helplessness. Sometimes the hallucinations don’t go away, but there is no medical cure.

Depending on the severity of the condition, treatment may include:

• Medical advice – talking it over with a doctor or counsellor can be helpful.
• Vision therapy – low-vision rehabilitation may help to ease symptoms.
• Moving your eyes – some people report that the hallucinations dissipate if they move their gaze from side to side or up and down.
• Changing the variables – to ‘turn off’ the hallucination, you could try altering the environment or setting that you are in. For example: if it’s dark, turn on the light, or if you’re standing up, sit down. If your eyes are open, shut them, or if you’re in one room, go to another room.

Where to get help

• Your GP (doctor)
• Optometrist
• Ophthalmologist
• Vision Australia Tel. 1800 033 660
• Macular Degeneration Foundation Tel. 1800 111 709
• Charles Bonnet Syndrome Foundation Tel. 1300 121 123