Charles Bonnet Syndrome


Research shows that many aging people experience vision loss. This can occur for a number of reasons, the most common of which are macular degeneration, diabetes-related vision loss, cataracts, or glaucoma. For many older people and those who care for them, this vision loss is, in and of itself, difficult. Learning new ways to safely navigate the world while also progressively losing vision is a tough obstacle. Unfortunately, losing vision may not always be the end of the story.

Charles Bonnet Syndrome

For some who experience progressive vision loss, visual hallucinations may also occur. Research suggests that as many as 60 percent of those who experience serious vision loss may develop mild, often brief, and non-aggressive hallucinations, referred to as Charles Bonnet syndrome, or CBS.

The name for these hallucinations came from Charles Bonnet, a Swiss writer who described his near-blind grandfather as suddenly having visions of things that were not there. It was almost as if he could suddenly see again, after years of lost sight.

The precise mechanics of this are difficult to define and discover…

Currently, there is no known cause for these hallucinations. It comes down to the relationship between the human brain and the human eye. It is difficult for the brain to become accommodated to vision loss, and so it is theorized that the brain compensates by creating false images in the vain hope of restoring vision. The precise mechanics of this are difficult to define and discover, since the nerves of the eye and the neurons of the brain are generally not as well understood as, for example, the interrelationship of the pancreas and blood glucose. The closest and most educated guess is that these hallucinations are the brain’s attempt to see without information coming from the eyes, attempting to create its own images without sensory input.

Most of these hallucinations are mild in nature they are projections of a brain desperate to get information from the world around it. The two major types of hallucinations caused by CBS are patterns or images. Patterns may be simple grids or shapes, and images may be people, places, animals, or selections from memories past, though these last are relatively rare.

CBS can occur during any part of the process of vision loss, but it tends to lessen with time as the brain grows more accustomed to the lack of information coming from the optic nerve. CBS is most likely to occur if vision loss is experienced in both eyes, perhaps because the brain is struggling to compensate for both eyes rather than just one.

What to Do if Your Senior is Hallucinating

Just because the senior in your care is experiencing vision loss does not mean that any hallucinations experienced are a result of CBS. Always see a doctor if a senior you care for is hallucinating at all, even mildly. Doctors will evaluate to see if the hallucinations are, in fact, CBS, essentially by ruling out other causes (such as mental illness or Alzheimer’s, both of which can cause hallucinations and are major causes for concern).

Hope for a Cure?

There is no current cure for CBS, but there are coping strategies recommended by the Charles Bonnet Syndrome Foundation. Improving vision, changing lighting or employing visual aids, or even taking certain medications can help decrease the number of hallucinations, but even these are not fully effective in most cases of CBS.

The end lesson is that hallucinations in those with vision loss may not be a sign of something incredibly serious, such as Alzheimer’s or mental illness, and may be a somewhat normal, innocuous form of the brain trying to work with its current limitations. Always see a doctor if these symptoms arise in a senior for whom you provide care, since at the least it will cause confusion (or even fear) in those whom it affects. However, hallucinations after vision loss are somewhat common and tend to become less frequent with time and may be mitigated at times by certain medications, environmental or behavioral changes.



Charles Bonnet Syndrome Foundation. FAQ. Available at Retrieved April 8th, 2016.

Canadian National Institute for the Blind (CNIB). What is Charles Bonnet Syndrome? Available at Retrieved April 8th, 2016.

Menon, G.J,. Rahman, I., Menon, S. J., and Dutton, G. N. (January/February 2003). Complex visual hallucinations in the visually impaired: the Charles Bonnet Syndrome. Survey of Ophthalmology, 48(1): 58-72. Available at Retrieved April 8th, 2016.

National Health System Choices (NHS Choices). Charles Bonnet syndrome. Available at Retrieved April 8th, 2016.

Royal National Institute of Blind People (RNIB). Understanding Charles Bonnet Syndrome. Available at Retrieved April 8th, 2016.