Vision Loss Can Cause Hallucinations: What Is Charles Bonnet Syndrome?

People with severe vision loss may sometimes begin to see people, flowers, buildings, or geometric patterns that are not actually there. Such visual hallucinations can be frightening, but in some cases they are not caused by a mental health condition or dementia. Instead, they may be linked to Charles Bonnet syndrome (CBS), a little-known consequence of vision loss, Medical Xpress reports.

According to research, Charles Bonnet syndrome occurs in approximately one in six people with retinal diseases or significant vision loss. The more severe the vision impairment, the higher the likelihood of experiencing such hallucinations. The syndrome is most commonly seen in people with age-related macular degeneration, a condition in which the macula, responsible for central and sharp vision, becomes damaged.

In the United States, approximately 11 million people have age-related macular degeneration, according to the National Eye Institute. The risk of developing the disease increases with age, particularly after 55.

Hallucinations associated with the syndrome can appear extremely realistic. For example, 97-year-old Brooklyn sculptor Varda Yoran, who had almost completely lost her sight, once saw a street on a hospital stretcher that did not actually exist. At home, she sometimes thought that unfamiliar people were sitting in her living room. She knew that what she was seeing was not real, but feared that she was losing her mind. Later, her daughter found information about Charles Bonnet syndrome, and her doctor confirmed that her symptoms were consistent with the condition.

The syndrome is not well understood not only by patients themselves but also by some doctors. Retinologist Surendar Purohit of the Specialty Eye Institute in Michigan told The Washington Post that patients had described seeing people, patterns, and geometric shapes that were not actually there.

Research on the brain conducted by Dominic ffytche, a professor of visual psychiatry at King’s College London, may help explain why this happens. When the visual cortex stops receiving the usual amount of input from the eyes, areas of the brain deprived of incoming information may become more excitable. As a result, neurons can begin firing spontaneously, creating visual images.

However, it is still unclear why the syndrome develops in some people with vision loss but not in others.

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