A Vision Specialist Reassures Clients About Charles Bonnet Syndrome

Engraving of Charles Bonnet in profile. File source: Wikimedia Commons. This image is in the public domain because its copyright has expired
Portrait of Charles Bonnet

As an itinerant vision rehabilitation teacher, I travel the highways of Central Indiana making home visits to people learning to adapt to vision loss. Each initial appointment begins on the front porch of a stranger’s home. When the door opens, I follow my new client inside to sit at their kitchen table. As I unpack the tools of my trade—tactile labels, magnifiers, talking watches—my clients confidently answer my routine questions about their eye condition, their ability to read print, or sensitivity to glare. There is an understandably more varied reaction, however, when I ask if they are having hallucinations of plants, animals, or people; "Did you know," I ask, "that it’s common for people who are losing sight to think they see things that aren’t there? It’s called Charles Bonnet Syndrome."

Sometimes I see a wave of relief pass over the client’s face. One elderly lady who had macular degeneration leaned forward to tell me that my car appeared to be covered in beautiful flowering vines when I pulled in the driveway. Another client living with glaucoma turned to his wife and said, "See, honey! Just because I see parrots in the houseplants doesn’t mean I’m crazy!"

Introducing Charles Bonnet

Curiosity piqued, they want to know about this Mr. Charles Bonnet and the tricks he plays on the eyes. And so I explain.

The syndrome was named for a French naturalist and philosopher who lived in the 18th century and first recognized the phenomenon. Charles Bonnet was aware that his grandfather was having hallucinations of handkerchiefs floating in the air and saw horse-drawn carriages and buildings appear out of nowhere. Noting that his grandfather was quite mentally sharp, Charles Bonnet attributed these hallucinations to his grandfather’s failing eyesight. Neurologists have since proved him right.

Your Eyes Are Just Dreaming

We think of blindness or a visual impairment as something that happens to our eyes, but the visual system is very much rooted in our brains. In Charles Bonnet Syndrome, the brain is no longer getting visual input or cannot make sense of the images impaired eyes are transmitting. Seeking stimulation, the brain rummages through its storage bins of past visual memories and simply invents something to look at. Or, as I explain to my clients, "You may be wide awake, but your eyes are dreaming."

Because these hallucinations are triggered by the part of the brain that is associated exclusively with vision, there is nothing to hear, touch, or taste. In a wonderful Ted Talk, the late neurologist and acclaimed author Oliver Sacks explains the difference between the noiseless hallucinations of Charles Bonnet Syndrome and hallucinations brought on by mental illness. The latter, explains Dr. Sacks, assaults all the senses and triggers a strong emotional response that compels the observer to engage verbally or physically with the hallucination. In contrast, the visual images of Charles Bonnet Syndrome don’t demand one’s attention and, in fact, seem to ignore the viewer. If a psychotic episode is more like being dropped into a virtual reality game, then Charles Bonnet is akin to passively watching a silent movie on an old film reel.

Charles Bonnet syndrome hallucination of a blue moose
Hallucination of a blue moose

Entertaining Hallucinations or Boring Visual Memories?

Many hallucinations have a surreal quality—elephants in the tomato plants or a large firetruck parked on the back patio—but a good percentage are so mundane that they might go unnoticed. Walking through a department store one day, Wendy admired the colorful array of purses on display until her friend pointed out they were in the lingerie section. Wendy tells me that many of her Charles Bonnet moments feature unremarkable, everyday objects such as a box of cookies on the counter, a grandfather clock in a hotel lobby, a flag in a parking lot. The tip-off, she notes, is that the hallucinations have a sharpness and detail that in reality, she is no longer able to see.

The vast majority of my clients see very pleasant images. They look forward to chatting with me about the river that came down the hallway of their assisted living facility or the colorful checkered patterns and interlocking circles that dance on their kitchen walls. One woman was comforted by the image of a little girl with a headful of colorful barrettes sitting on the end of her bed. "I thought she was an angel," She confided, a bit disappointed.

Nina, a lawyer and mother of five, is quite delighted by the fact she has Charles Bonnet Syndrome. Nina’s first experience occurred when she was putting up holiday decorations and alerted her family to the playful bears shimmying up the Christmas tree. After some quick research on the Internet, the family agreed Nina had a case of Charles Bonnet Syndrome. These days Nina looks forward to her Charles Bonnet moments. In fact, she confesses to occasionally slipping away to a dark room where she squints until her inner eye conjures up some images. She says, "I’m bored. Bring me something good, Charles Bonnet!"

Shake Off Unpleasant Hallucinations

Not all visual hallucinations are pleasant. One client was cheered by the image of her sister as a young girl wearing her favorite blue dress but was less thrilled to see spiders on her bedroom quilt. Some disturbing images feature common themes such as deformed faces. One gentleman told me that he couldn’t see his television well, but it always seemed that the newscasters had very distinctive, over-sized teeth that glinted. In Oliver Sacks’ Ted Talk, he explains that certain visual cells are associated with specific images. It seems that the visual cells that correspond to teeth and eyes, as well as those that are associated with cartoon characters and geometric patterns, are most frequently triggered in Charles Bonnet Syndrome.

It’s easy to be rattled if one suspects that the vision loss is accompanied by an undiagnosed mental illness. And of course, it’s no surprise that my elderly clients, fearing dementia, keep secrets from their adult children. But the vast majority of people can live at peace with Charles Bonnet Syndrome once they understand the cause.

The good news about unwelcome hallucinations is that they usually can be disrupted by flicking on lights, blinking, or turning one’s head away. So far, there is no medication for the condition although doctors who misdiagnose the syndrome may mistakenly prescribe anti-psychotic medicine. The website of the Royal National Institute of the Blind (RNIB) explains why anti-psychotics are not advised and offers solid advice for dealing with distressing Charles Bonnet experiences. One word of caution: Sometimes consultation with a neurologist or other specialist is necessary to rule out any serious disorders that may mimic Charles Bonnet syndrome [such as migraine, epilepsy, brain tumors, dementia, Parkinson’s disease, or mental illness}.

Getting the Word Out About Charles Bonnet

Neurologists estimate that 10 percent of people with vision loss will experience Charles Bonnet Syndrome but only one percent of them will admit to it. I enlist the support of my clients to take Charles Bonnet Syndrome out of the shadows and into the limelight. Some return to their ophthalmologists and encourage them to distribute information about the syndrome to new patients. I like to picture my clients holding court at parties in their Senior residences and at family gatherings as they freely share lighthearted anecdotes about their Charles Bonnet moments. As the word gets out, more people will be fully prepared when they encounter a visual hallucination for the first time. Instead of recoiling in fear, they will simply nod and smile knowingly at the apparition, "Hello there. I’ve been expecting you Charles Bonnet."

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