Brian Alexander writes:
The 69-year-old man saw the spider clearly, whacked at it, yet the spider wouldn't die. At night, people he knew started visiting his bedroom, sitting in the armchair beside his night table. But he hadn't invited them. Oh, and there were animals roaming around his house.
A different patient saw a double decker bus in the living room. Another saw fire hydrants just like the one that used to sit in front of her childhood home. Then there was the woman who saw small children sitting atop her piano. She didn't know them and had no kids of her own, but there they were.
These people, whose cases were documented in medical journals, are not crazy.
They are affected by a condition called "Charles Bonnet syndrome," (pronounced bow-NAY), a somewhat common hallucinatory condition among people suffering various forms vision loss. The condition was named for an 18th-century naturalist who described it in his grandfather.
Recently, Ed Connors, a 61-year-old software engineer near Boston saw a woman walking her dog on his street. In reality, it was just a shadow. Sometimes when in a shopping mall, Connors thinks he sees people and will move to get out of their way. Except nobody is there.
Connors has a disease called vitelliform macular dystrophy or Best Disease that has impaired his vision. He was diagnosed with it about 10 years ago. "Shortly after that," he said, "I started seeing phantoms."
People who experience these kinds of hallucinations are typically thought to suffer from dementia, Alzheimer's or some other psychiatric illness, Dr. Mary Lou Jackson of the Massachusetts Eye and Ear Infirmary explained. Actually, Connors and other people experiencing the syndrome are mentally healthy, but are frequently misdiagnosed.
Often, "patients are afraid to tell doctors they are hallucinating for fear of being thought they're crazy," she said. "It takes good clinicians to spend time to realize the person is clear thinking."
The disorder occurs when there is a total or partial disconnect along the path between the eyes and brain's visual cortex. That disconnect can be caused by any number of diseases and conditions – glaucoma, diabetes and stroke, for example — as well as injuries. In the absence of real visual information the brain is liable to make up images of its own.
"If the primary visual cortex does not get a message, that means subsequent stops [on the path of a visual image] are not getting them either," Jackson said. "That lack of a message into the brain triggers the other parts to put pictures there spontaneously."
For years the syndrome was thought to occur almost exclusively among the elderly, but recent research shows it can happen to anybody.
A small study by Harvard Medical School researchers tested the mechanism of the syndrome on 13 people with normal vision. They wore blindfolds for five days. Ten of the 13 experienced hallucinations after an average of one day.
Often the hallucinations are not as elaborate as an elephant in the living room — a common vision among people with the syndrome — or phantom children playing piano. Many of the images consist of geometric patterns. There is some controversy over what standards to use for diagnosing the condition. Some doctors will diagnose Bonnet syndrome if patients see flashing or colored lights, but others disagree.
Most people who experience Bonnet syndrome are either not troubled by it or may actually find it pleasant. For example, many see loved ones who have passed away, or images re-created out of a fond memory. They know the people aren't really there, but enjoy the visit.
The prevalence of Bonnet syndrome among visually impaired people can vary widely, ranging from 2 percent up to 33 percent depending on the estimate. Roughly a quarter of Bonnet syndrome cases resolve themselves as mysteriously as they began after about a year, Jackson believes. Some may last weeks or many years, like Connors'. There's no specific treatment — for most patients, simply realizing what's going on is comforting enough.
In fact, Connors has adapted to his visions so he's usually able to suss out when what he's seeing is real or not real. While he never feared he was losing his sanity, receiving the diagnosis from Jackson eased his mind. "I was relieved to know it had a name and to hear how common it was."