I Can’t Believe My Eyes: Life With Bonnet Syndrome

Hallucinations, therefore moments of perception of stimuli that are not present at the given situation, can have multiple causes. From use of addictive substances such as hallucinogens or other psychoactive substances across hypnotic suggestions to extreme physical or mental exhaustion of an organism, experienced for example by endurance racers or ultra-marathon runners. In all cases, sources of hallucinations can be recognised and relatively easily removed. Addictive substance can be withdrawn, hypnotic session can be terminated, races can be finished or given up. There are, however, also patients whose hallucinations possess more persistent issue. Hallucinations have been recognised as possible symptom of neurodegenerative disorders, such as Alzheimer’s disease [1], schizophrenia [2] or Charles Bonnet syndrome, the focus of this article. In contrast to former two conditions, patients with Charles Bonnet syndrome do not display any other psychiatric symptoms. Therefore, even though hallucinations being reported are recognised as vivid and possessing high level of complexity, patients remain fully conscious of the fact that their apparent perceptions are inconsistent with reality.

source: www.retinalphysician.com

source: www.retinalphysician.com

The condition was first described in 1769 by a Swiss philosopher Charles Bonnet. Bonnet observed that his grandfather, Charles Lullin, had developed vivid visual imaginations of human figures, beasts and buildings, while remaining mentally sane and, as Bonnet recorded, never considering those images being reflections of reality in any way. From that observation, and from notion of the fact that his grandfather had subjected to medical surgery to remove cataracts in his eyes, Bonnet concluded that those visual hallucinations were result of damage to visual pathway, rather than signs of cognitive impairment. His idea was later enhanced by Bonnet’s own experience, when he developed the same bizarre visions which, as he reportedly said to his biographer, he had always recognised as being mere illusion [3]. Bonnet’s work, along with similar cases being reported by Naville (1873) and Flournoy (1923) then led de Morsier (1938) to define the condition as “hallucinations visuelles apparaissant chez les vieillards sans déficience mentale”, therefore visual hallucinations appearing in elderly people who otherwise do not display mental deficiency. De Morsier was then the first person to officially name the condition as Charles Bonnet Syndrome.

In spite of the fact that the syndrome was first described almost 80 years ago, there is still an ongoing dispute as to exact definition of the condition. While some researches consider all those who suffer by complex visual hallucinations while remaining fully conscious of unreality of those images as suffering by Bonnet syndrome, the other papers condition the diagnosis by condition developing as a result of eye disorder [4]. Some authors go even further in calling for specification of description of exact extent and type of vision disorder, so for example those who suffer by post-eye surgery hallucinations or decreased visual acuity may be excluded, even though they otherwise display all symptoms of the syndrome. The part abut disorder affecting only elderly patients has also been questioned, as above mentioned de Morsier himself recorded similar symptoms in 16 other cases in age group 10 to 59 years of age [3]. The most plausible explanation is that disorder can emerge in any age, but the probability increases with age as a result of general weakening of eye muscles and related loss of sight.


Comparison of normal and Bonnet vision. Image source: Lighthouse International – Charles Bonnet Syndrome


It is the loss of sight that is most often related to the development of the condition. Even though an exact cause still remains unclear, the Bonnet syndrome often accompanies loss of central vision and cataracts. That signalises that Bonnet syndrome might be a response of the brain to decrease in level and quality of visual stimuli. Bonnet syndrome thus can be seen as a compensation mechanism of the “bored” visual cortex, or as an attempt of the brain to fill gaps in visual processing caused by discontinuity of actual stimuli. It’s also good to say that most of patients report improvement of the symptoms over time, probably due to gradual adaptation of the brain to new visual conditions. It therefore seems that the main antecedent of development of the disorder is an age-related change in interaction between brain and eye, induced most probably by changes inside patient’s eye.

If little is known about causes, then even less we know about treatment. As the disorder is apparently not triggered by cognitive changes or by changes in perception, it can be supposed that most of conventional drugs would probably be inefficient. Most of the contemporary treatment is therefore focused on improvement of mental well-being of patients and on handling of the situations when hallucinations emerge. Patients are advised to change light conditions, to perform mild physical activity, and also to perform actions which allow them to take perceived control over the situation, such as expressing their awareness of hallucinations not being part of the real world or getting “familiar” with usual form and content of their visions. Patients are also reassured that even though vivid visions might be unsetting and difficult to cope with, they are usually not explicitly threatening or distressing, and they are not accompanied by cognitive deterioration.

The greatest issue of Charles Bonnet syndrome for those affected thus seems to be not in medical condition itself, but in stigmatisation of hallucinations as a sign of “madness” or dementia and in low awareness of the existence of such diagnosis. As Judith Potts, founder of Esme’s Umbrella, a UK-based organisation for those suffering by Charles Bonnet syndrome, recalls, her mother’s GP had never heard of the condition before Mrs Potts expressed her opinion that her mother might have been suffering from it. Since then, situation has slightly improved, but the stigma of hallucinations being inherently related to false beliefs and cognitive distortion is unfortunately still embedded in public awareness about mental conditions.



1. Mega, M.S., Cummings, J.L., Fiorello, T. and Gornbein, J., 1996. The spectrum of behavioral changes in Alzheimer’s disease. Neurology, 46(1), pp.130–135.

2. Jablensky, A., Sartorius, N., Ernberg, G., Anker, M., Korten, A., Cooper, J.E., Day, R. and Bertelsen, A., 1992. Schizophrenia: manifestations, incidence and course in different cultures. A World Health Organization ten-country study. Psychological medicine. Monograph supplement, .

3. Berrios, G.E. and Brook, P., 1982. The Charles Bonnet syndrome and the problem of visual perceptual disorders in the elderly. Age and ageing, [online] 11(1), pp.17–23. Available at: <http://www.ncbi.nlm.nih.gov/pubmed/7041567>.

4. Pearce, J.M.S., 2008. Charles Bonnet’s Syndrome. Neurology and Literature, 8(5), p.19.

Image 1:  www.retinalphysician.com

Image 2: “Lighthouse International – Charles Bonnet Syndrome”. Li129-  107.members.linode.com.

Feature image: www.wellhappypeaceful.com/wp-content/uploads/2011/03/Stars_in_Your_Eyes.png

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