Vision loss can make people see things that aren’t there
Losing your vision can make the world disappear. For some people, it can also make
them see things that are not there.
People with significant vision loss sometimes experience vivid hallucinations of people, animals, buildings or patterns. The phenomenon, known as Charles Bonnet syndrome, can be unsettling, particularly when people do not know why it is happening. Charles Bonnet syndrome is a condition where people with significant vision loss experience visual hallucinations.
Dr. Hongli Wu, associate professor, pharmaceutical sciences, College of Pharmacy and Health Professions, and associate professor, North Texas Eye Research Institute, explains that Charles Bonnet syndrome is especially common in people with age-related macular degeneration. However, it can occur with other causes of severe vision loss. Wu also mentions that hallucinations can be remarkably vivid.
“They may see people, animals, flowers, buildings, landscapes, patterns, or geometric shapes,” Wu said. “Many people with CBS understand that what they are seeing is not real, even though the images may look extremely convincing.”
We asked Wu to explain more about Charles Bonnet syndrome and the connection between the eye and the brain in those impacted by the syndrome.
How can losing vision cause the brain to produce images that aren't really there? What do we understand about what's happening between the eyes and the brain?
A simple way to think about it is that the brain is used to receiving a constant stream of visual information from the eyes. When vision is lost, that stream of information becomes much weaker. But the visual parts of the brain do not simply shut down. Instead, some of those brain cells may become more active on their own. In a sense, when the brain is no longer receiving enough information from the eyes, it may begin generating some visual activity itself. Brain imaging studies have shown that different visual areas can become active depending on the type of image a person is seeing.
People who experience these hallucinations may worry that they're developing dementia or another mental health condition. How can they tell the difference between Charles Bonnet syndrome and hallucinations caused by something else?
An important feature of Charles Bonnet syndrome is that the person usually has significant vision loss and realizes that the images are not real. Their thinking may otherwise be completely clear. That is different from some conditions in which hallucinations occur together with confusion, changes in memory, or difficulty distinguishing reality from what is being seen. However, it is critical that people not diagnose themselves and should consult with a physician, in case there are other possible causes.
Why do some people with significant vision loss experience these hallucinations while others don't? Are there particular risk factors that make someone more susceptible?
There are still some unknowns about why some people develop Charles Bonnet syndrome, and others do not. It appears more common in people with more severe vision loss and age-related macular degeneration is one of the conditions most often associated with it. Researchers think the brain may adapt differently from person to person after vision loss. In some people, these changes may make the visual system more excitable and likely to produce hallucinations.
The hallucinations can reportedly be incredibly vivid—people, animals, landscapes, or patterns. Is there a typical pattern to what people see and does what they see tell us anything about what's happening in the brain?
There is no single image that everyone with Charles Bonnet syndrome sees. While some people see simple patterns, shapes or textures, others might see detailed people, animals, buildings or entire landscapes. Interestingly, the type of image may tell us something about which part of the visual system is active. Brain imaging studies suggest that areas involved in recognizing patterns may become active when someone sees patterns, while areas that process more complex scenes may be involved when someone sees landscapes or other detailed images.
If someone with vision loss suddenly starts seeing things that aren't there, what should they do first and what should their family or caregiver do?
The first step is to talk about it rather than hide it. People may be afraid that they are developing dementia or a psychiatric illness, but these experiences can be related to vision loss. A patient should inform their eye doctor or primary care provider. This way, the condition can be evaluated, ruling out other conditions. Caregivers should remain calm, listen carefully and avoid immediately assuming that the person is confused or mentally ill. Simply understanding that Charles Bonnet syndrome exists can greatly reduce fear.
Can anything be done to make these hallucinations less frequent or less frightening, and do they tend to go away over time?
One of the most helpful things is understanding what is happening. Once people know that the images can be a response to vision loss rather than a sign that they are “losing their mind,” the experience often becomes much less frightening. There is not one specific treatment that reliably stops the hallucinations in everyone. The encouraging news is that, for many people, hallucinations become less frequent and less intense over time, although they may not disappear completely.
There is currently no evidence that Charles Bonnet syndrome itself is an inherited condition, as no specific gene has been identified as causing it. Researchers believe this syndrome is more closely related to how the brain adapts when it receives less visual information after significant vision loss. There are still some unknowns about why some people develop these hallucinations while others do not, even with similar vision loss.
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