People with Charles Bonnet syndrome can vouch for the cliché that things aren't always as they seem. This syndrome, named for the eighteenth-century philosopher who first described it, is characterized by visual hallucinations. People may see anything from abstract patterns to birds and babies and white sandy beaches. These hallucinations tend to occur during down time--say, while getting a haircut or waiting in line at the dollar store.

Simulation of Charles Bonnet Syndrome: a normal street scene next to a street scene with monkeys

The folks who perceive these visions know they're just mirages, of sorts. That is, the images are illusions, not delusions. The difference is that a person with delusions is convinced that what she sees is real. Patients with Charles Bonnet syndrome may initially second-guess themselves but they ultimately accept that their perceptions have no substance.

The cause of this disorder is thought to be a misfire in the brain similar to the neurological mixup that occurs in patients with phantom limb syndrome. As vision wanes, the brain continues to interpret visual imagery in the absence of corresponding visual input, just as it sometimes continues to process pain signals from a limb that's no longer there.

Charles Bonnet syndrome has one principal symptom: the periodic occurrence of hallucinatory visions. Sometimes the hallucinations are very animated and detailed.

A person who has such visual illusions may wonder if he's becoming mentally ill or developing senile dementia. He may hesitate to tell his doctors or loved ones about the problem for fear they'll draw that very conclusion.

Risk factors
Roughly one third of patients with low vision develop Charles Bonnet syndrome, including those with age-related macular degeneration, cataracts, diabetic retinopathy, and other eye disorders. The hallucinations are more likely to occur when the person is awake, alone, and in dim light, or when he or she is physically inactive or lacks distractions, such as television.

Turning on an extra lamp or two, staying physically and mentally occupied, spending time with family or friends, and participating in social activities can reduce the frequency and vividness of the hallucinations. Each patient must learn what works for him or her. A positive attitude is the key.

Your eye care professional is the best healthcare professional to diagnose this condition. In addition, your eye care provider will already be aware of any underlying vision disorders you have that may be associated with the syndrome. A thorough eye examination to rule out additional problems and a few targeted questions about your symptoms are usually all that's needed to diagnose the syndrome.

Sometimes consultation with a neurologist or other specialist is necessary to rule out any serious disorders that may mimic Charles Bonnet syndrome, such as stroke and Parkinson's disease. The diagnosis may be complicated by the fact that many patients have multiple medical problems, such as diabetes and heart disease, for which they take several medications.

Fortunately, the saying "This, too, shall pass" is also true for those with Charles Bonnet syndrome. After a year or perhaps 18 months, the brain seems to adjust to the person's vision loss, and the hallucinations begin to recede.

In the meantime, of course, the underlying visual impairment should be treated or monitored. Idle time should be kept to a minimum. If the person is found to be depressed, therapy or pharmacologic treatment may be in order. Antiseizure medications have been shown to calm the hallucinations in some patients, and antianxiety agents can be used in those who find the visions upsetting. For most patients, though, just knowing that they aren't becoming mentally ill and that the symptoms will eventually subside is all the treatment they need.



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