Q: Not long after my eyesight started to deteriorate from AMD, I began having hallucinations. Am I losing my mind?

A: You’re definitely not losing your mind. You’re experiencing Charles Bonnet Syndrome (CBS). Bonnet was an 18th century Swiss philosopher who first realized that some people who undergo a loss of vision can experience detailed visions such as images of little people in elaborate, coloured costumes dancing and doing other things. Or three people sitting on your living room couch, which you know is empty. Some people with CBS might see just one face. Or purple squares all over the wall.

Not everyone experiences CBS, however. Our studies indicate that about one-third of people who have partial vision loss are affected.

Is there a connection between the extent of vision loss and CBS?

Most researchers don’t find a direct relationship between the extent of vision loss and CBS. Some say if your vision gets worse the hallucinations go away. Others say if your vision gets better they will go away. We don’t know yet. But we do know that you don’t have to have a lot of vision loss to experience CBS. You might still have enough visual acuity to drive, for example. But if you’ve got an eye disease, maybe macular degeneration, maybe glaucoma, and you have partial vision loss, you could have CBS.

What causes CBS?

Our best guess is that it’s like a phantom limb sensation. If someone has their leg amputated they can sometimes still feel their toes even though they’re not there. What they have is an area of the brain that represents the toe. And we believe it’s the same with vision. You’re not getting input into a specific area of the brain where you should get vision messages. And that lack of getting the message somehow allows the brain to put an image in there.

For some, CBS is a short-term phenomenon. They get it one day and it might last a week or two and then never returns. Others have it absolutely every day. They get so used to it it’s like brushing their teeth. If you ask them, did you have it today? they’ll say, “Oh, maybe I did. I’m not sure.” The frequency of it occurring varies widely.

I should mention that not all visual hallucinations are due to CBS. Other disorders such as psychiatric disease, neurological disease or side-effects of medications can cause hallucinations. It is important not to rely on self-diagnosis for CBS. You should discuss your symptoms with your doctor so that an accurate diagnosis can be made. If you think your doctor might not be familiar with CBS, try bringing this article in with you when you visit.

Treatments vary

Most patients benefit from reassurance and require no other treatment. We believe people experience CBS more when they are a little subdued. I always tell people who want to get rid of hallucinations to try and be more active. Keep the radio on. Put more lights on in your home. Go out more often. Patients who are extremely bothered can be assisted by medications prescribed by a psychiatrist.

CBS is underreported

Because some people with CBS fear they have Alzheimer’s, dementia or some other disease, they don’t tell anyone about their visions. Or if they tell their doctor, he or she might misdiagnose the problem because there’s still a lack of recognition in the medical community about it. Fortunately, that is changing but there’s still the need to inform both patients and medical practitioners about CBS. I always recommend patients read Macular Degeneration: The Complete Guide to Saving and Maximizing Your Sight, by Lylas and Marja Mogk. It has a chapter on patients’ experiences and their drawings of what their hallucinations look like when they have CBS. It will show you that you are not alone.

Colour picture of Dr. Mary Lou Jackson

The Expert

Dr. Mary Lou Jackson is an ophthalmologist at the University of British Columbia, Department of Ophthalmology. Her research specialty is contrast sensitivity and visual hallucinations in patients with vision impairment. She obtained her MD from McMaster University in Hamilton, ON, and did her residency at the University of Toronto.