Though not a specific eye condotion, Charles Bonnet Syndrome (CBS) is the term used for the situation when people with sight problems have vivid and recurrent visual hallucinations and see things that aren't there.
CBS was first described by Swiss philospher Charles Bonnet in 1760 when his almost blind grandfather noticed seeing a range of birds, objects, patterns, buildings and even people that weren't there.
CBS affects people with serious sight loss and usually those who have lost their sight later in life.
Symptoms:
Visions can range from regular patterns, like brickwork, lines or netting to more complex pictures, objects or people, even whole scenes. They can be in black and white or colour and objects can appear larger or smaller than the real life equivelent. These hallucinations are purely visual and don't stimulate other senses such as smell or touch. These images seem to appear out of nowhere and can last for a few minutes to a few hours.
It is thought that between 10% and as many as 40% of people with sight loss experience Charles Bonnet syndrome. The exact number isn't known as many people don't admit to having hallucinations for fear of being labelled mentally ill, which they are not.
Causes:
Little is still known about Charles Bonnet syndrome and what causes it. It is still unknown exactly how the brain processes images but it is thought that the syndrome affects people who have lost sight because the brain is no longer processing incoming images, so it releases old, stored pictures, to make up for the lack of visual stimulation.
Treatment:
As the exact cause is unknown, other than the brain "playing tricks" on the sufferer due to underlying sight problems, there is no actual cure. However, most cases generally disappear after about a year to 18 months.
Hallucinations can be quite disturbing but as long as the sufferer understands that it is just the sight loss causing the visions, then ignoring or coming to terms with them can be the most effective way of dealing with them. Sometimes the pictures can get in the way of what vision the patient has left, so can be quite problematic. Some suffers find changing conditions, such as turning on lights if its dark, blinking, changing position (standing up if sitting) etc can "reset" the vision and get rid of the hallusination.
Other health conditions can cause hallucinations, such as Altzheimer's, strokes or mental illness but suffers should be aware it is their vision problems causing the syndrome.
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