Charles Bonnet Syndrome
By Lylas G. Mogk M.D., Marja Mogk Ph.D.,
And Carol Sussman-Skalka, CSW, MBA

Do you ever see things you know are not there but look real anyway? It’s a common side effect among people with visual impairment. While we refer to it as “phantom vision,” the technical term is “Charles Bonnet Syndrome.” If you’ve experienced this, rest easy. Your mind is fine – your eyes are playing tricks on you.

Charles Bonnet, an 18th century Swiss naturalist and philosopher, is credited as the first person to describe the syndrome. Like his grandfather who had low vision and saw men, women, birds, and buildings he knew were not there, Charles experienced similar phantom visions when his own vision deteriorated. This condition is often described as being similar to the phantom limb that is experienced by those who have had a limb amputated but still feel it even though it is not there. This happens because the limb’s nerves are still active and sending signals to the brain, which the brain interprets as sensations from the missing limb. Similarly, when retinal cells become impaired and are no longer able to receive and relay visual images to the brain, the visual system begins firing off images on its own. Studies show that this syndrome affects between 10 and 40 percent of people with low vision. Research suggests that it is more likely to appear if you have visual acuity between 20/120 and 20/400. If your vision falls within these parameters, your eyes still have a great deal of power even though they aren’t receiving and sending as many images as previously. As a result, your eyes may be providing additional images of their own. There is no way to predict whether you will see images and, if you do, how frequently they will occur or how long they will last. You may never experience Charles Bonnet Syndrome, you may have it for only a few months, or you may have it for years. You may see images every day, a few times a week or several times a month.

Charles Bonnet Syndrome is not a psychiatric problem. It is no more than a side effect of vision loss. Mogk and Mogk give the six criteria for images typical of Charles Bonnet Syndrome:

  • “They occur when you are fully conscious and wide awake, often during broad daylight.
  • They do not deceive you; you are aware they are not real.
  • They occur in combination with normal perception, such as a clear sidewalk covered with dots, flowers, or faces.
  • They are exclusively visual and do not appear in combination with any sounds or bizarre sensations.
  • They appear and disappear without obvious cause.
  • They are amusing or annoying but not grotesque.”
Mogk and Mogk go on to state, “Since ophthalmology has paid so little attention to Charles Bonnet Syndrome, many doctors don’t realize how common it really is, and some may not be familiar with it at all.”

Is Charles Bonnet Syndrome Treatable? A majority of people do not find their phantom vision disturbing, probably because the images they see are amusing, pleasing, or entertaining. You may want to discuss your phantom vision with your doctor, particularly if you are bothered or distressed by your experiences. While there does not seem to be any specific medications that work for everyone, many find that learning more about the condition helps to reassure them.

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