One woman saw a fully dressed Royal Canadian mountie in her living room. Another saw the same red brick building in every part of town, as well as in the country. One man saw monkeys with red hats and blue coats playing in his yard.
They were all experiencing Charles Bonnet (“bo-nay”) Syndrome.
“Do you ever see something you know is not there, but it looks real?” It’s a question that Lylas G. Mogk, M.D., and Raman Deol, O.D., of the Henry Ford Center for Vision Rehabilitation and Research in metropolitan Detroit, always ask their low-vision patients.
Low vision that cannot be improved through corrective lenses or surgery can be the result of macular degeneration, glaucoma, diabetes, stroke, or other causes.
Some of their patients respond that they see purple flowers everywhere, even in winter. Others see animals, people, buildings, or geometric, quilt-like patterns. They rarely share their experience with their families, for fear of being misunderstood. Some wonder whether the visions suggest early dementia.
In 1789, Swiss naturalist Charles Bonnet described the visions of his father-in-law, who had low vision and saw people, animals and other objects that he knew were not real. Bonnet himself experienced phantom visions later in his life, similar to those of his father-in-law. Bonnet’s discovery went largely unnoticed for 150 years until the 1930s, when doctors rediscovered his files and named the syndrome after him.
The frequently undiagnosed Charles Bonnet Syndrome is very common, affecting 20 – 30 percent of those with low vision. Some may experience it for a few months, others for several years. The images can occur daily or only occasionally, with the same image appearing to the same person. There is no cure, but most people are not bothered by the images, and many find them interesting or amusing, especially once they understand it’s just their eyes playing tricks on them.
Although the cause is not known, the images can be compared to the “phantom pain” that can be felt by people who have had a limb amputated. The nerves that were connected to the missing limb still send signals to the brain. In our visual system, the nerves no longer receiving visual messages can cause the brain to “see” realistic images, while recognizing they are not real.
Many physicians are not yet aware of Charles Bonnet Syndrome, and may mistake it for psychotic hallucinations. Patients with the syndrome have been misdiagnosed and prescribed anti-psychotic medications.
To identify Charles Bonnet Syndrome, ophthalmologists use these criteria:
• The person has low vision.
• The images occur when the person is conscious, with open eyes.
• The person recognizes the images are not real.
• The same image appears repeatedly, superimposed on the real world. For example, the person sees a room normally, but the wall appears to have flowers on it and only that same image of flowers recurs to that same person.
• Images are only visual; they may move, but there are no sounds or smells. It’s like seeing a picture, or watching a silent movie.
• Images are common, familiar objects. They may be amusing or mildly annoying, but not frightening.
People with low vision who believe they may be experiencing Charles Bonnet Syndrome should discuss it with their ophthalmologist.
The Henry Ford Center for Vision Rehabilitation and Research is located in Grosse Pointe and Livonia, Michigan. It is the only center of its kind in the Midwest.