A few days after I wrote about conditions that can mimic dementia, reader Sue Murray emailed me from Westchester County. Her subject line: “Have you heard of Charles Bonnet Syndrome?”
I hadn’t, and until about six months ago, neither had Ms. Murray.
Her mother Elizabeth, who is 91, has glaucoma and macular degeneration, and has been gradually losing her vision, Ms. Murray explained. So at first, her family was excited when Elizabeth seemed to be seeing things more clearly. Maybe, they thought, her vision was returning.
But the things she was seeing — patterns and colors, strangers, a green man — weren’t there. She insisted that “there were people in the cellar, people on the porch, people in the house,” Ms. Murray said. “She’d point and say, ‘Don’t you see them?’ And she’d get mad when we didn’t.”
Elizabeth and her husband Victor, 95, live in Connecticut, in a house they bought 50 years ago. For a while, the Green Man, as Elizabeth began calling him, seemed to have moved in, too. “She’d start hiding things in the closet so the Green Man wouldn’t take them,” Ms. Murray said. “There wasn’t any real fear; it was just, ‘Look at that!’”
Elizabeth’s ophthalmologist promptly supplied the name for this condition: Charles Bonnet Syndrome, named for a Swiss philosopher who described such visual hallucinations in the 18th century. “We were relieved,” said Ms. Murray. What they feared, of course, was mental illness or dementia. “To have an eye doctor say, ‘I’m familiar with this,’ it’s still jarring but it’s not so terrible.”
Bonnet Syndrome (pronounced Boh-NAY) isn’t terribly rare, it turns out. Oliver Sacks described several cases in his 2012 book, “Hallucinations.” Dr. Abdhish Bhavsar, a clinical spokesperson for the American Academy of Ophthalmology and a retina specialist in Minneapolis, estimates that he has probably seen about 200 patients with the syndrome over 17 years of practice.
Like Mrs. Murray’s mother, his patients with Bonnet Syndrome have reduced vision — usually age-related macular degeneration, glaucoma or cataracts. Various European studies have found that approximately 10 to 15 percent of older adults with low vision or macular degeneration develop the condition; some studies have found higher rates.
But with about 2.1 million Americans over age 50 suffering from macular degeneration alone, that’s a lot of people seeing things.
“The numbers are all across the board,” said Dr. Bhavsar, who thinks the rate of Bonnet Syndrome is closer to 10 percent among those with low vision. But since these eye diseases occur more often in older adults, whose numbers are increasing, ophthalmologists will be seeing more cases — if patients aren’t too fearful to tell their doctors or families what is going on.
“They want to know if they’re going crazy, and we say, ‘Absolutely not, you are not losing your marbles,’” Dr. Bhavsar told me in an interview. “Dispelling that, saying it’s a known phenomenon with a name and that nothing else is wrong with them, they immediately feel relieved.” Even if, like one patient, they continue to see squirrels popping out of the ground.
The hallucinations, he explained, can occur intermittently — a few times a day or weeks apart — or nearly constantly. They can last seconds or minutes. Frequently they dissipate in a year to 18 months, but not always.
(Most respondents to a recent British survey said their hallucinations had lasted for more than five years, and roughly a third said they had experienced fear and some loss of normal activities. That the surveys were distributed to members of a national vision charity might have influenced those findings.)
The problem doesn’t originate in people’s eyes, but in their brains, which appear to misinterpret the reduced visual signals. The hallucinations are purely visual; someone who also hears things has something other than Bonnet.
Though there is no effective treatment, most of his patients cope reasonably well, Dr. Bhavsar said. Some are amused by what they call their own private movies. Counseling at low-vision rehabilitation centers can help people adjust.
Silence isn’t golden in these cases. Seeing an ophthalmologist won’t stop people from seeing patterns, animals and faces, but it can provide reassurance that they are not facing diseases most people find much scarier. One Minnesota internist thought his elderly patient had schizophrenia and was on the verge of prescribing psychotropic meds until he consulted Dr. Bhavsar, who explained about Bonnet Syndrome.
In Connecticut, where Sue Murray and her siblings work hard to keep their parents at home, the bizarre has become fairly normal. There is not much to do but wait it out.
The Green Man has stopped showing up, “but there’s a woman now and my mother’s convinced she’s after my father,” Ms. Murray said. “She says, ‘That woman’s here.’ I say, ‘Tell her to go away.’ The Green Man is gone and we’re hoping the rest will disappear, too.”