Seeing without believing

How often do you ask your visually impaired patients the following question: “Do you ever see things you know aren’t real?”

This is an important question that is often overlooked. Patients rarely volunteer information about hallucinating for fear of people thinking they are crazy or psychotic. If the patient is symptomatic, it is important to provide information about Charles Bonnet Syndrome (CBS), which is characterized by complex, vivid visual hallucinations experienced by people with vision loss. A key factor in making the diagnosis is that the patient knows the visual images are not real – they are hallucinations, not delusions.

Charles Bonnet

The phenomenon was first described by a Swiss philosopher and writer, Charles Bonnet in the 1760s when he documented a range of visual hallucinations in patients who appeared psychologically intact. This included his 89-year-old grandfather’s experiences after his grandfather lost his sight to cataracts and began having “visions”; he could see patterns, people, birds and buildings, which were not really there.

The prevalence of CBS varies in the literature from 10-40% but has been reported as high as 60% (iii). Unfortunately, accurate data is difficult to acquire, as people often do not report symptoms. The types of hallucinations can appear in many ways: as simple shapes and colors, or as detailed pictures of animals, landscapes or people.

What your patient may experience

It is normal for your patients to be distressed, confused or frightened by the visual images, however, don’t be surprised if your patients show no or little concern because they know the images are not real. Take a moment to explain that the visual hallucinations are caused by vision loss and not a sign of a mental health problem. Describing CBS as similar to “phantom limb syndrome” (the sensation that an amputated limb still has sensation) may help the patient understand the phenomenon. When vision loss occurs and the brain no longer receives sufficient visual information, the brain continues to create visual stimulation in the absence of visual input.

CBS is a “diagnosis of exclusion,” which means that the diagnosis can be made if there are no other neurological diagnoses to explain the hallucinations. If there are additional neurological problems or symptoms such as memory loss, weakness, a tremor or other senses impacted (hearing, smell, taste, or touch), a patient should be referred to a neurologist to rule out other conditions that could be contributing to the hallucinations.

Initially, the hallucinations may happen often but usually, reduce in frequency over time. Many patients describe that most symptoms occur during times of inactivity when they are daydreaming or relaxing. Unfortunately, there are no cures for CBS, however, there have been reports that staying mentally or physically active may help to reduce symptoms.

Some reports have suggested that eye exercises (moving eyes back-and-forth or changing fixation) could lessen symptoms. Anticonvulsants may be effective in reducing the hallucinations and anti-anxiety medication may be helpful for patients who are distressed by the syndrome (iii). Most importantly, emotional support, such as peer groups or counseling, maybe the greatest help in managing the condition. For most individuals, however, explaining the condition and providing reassurance is often sufficient for the patient to accept the condition.

  • (i) Hart J. Phantom visions: real enough to touch. Elder Care 9:30-2, 1997
  • (ii) Gold K, Rabins PV. Isolated visual hallucinations and the Charles Bonnet Syndrome: a review of literature and presentation for six cases. Compr Psychiatry, 1989:30:90-8.
  • (iii) Menon GJ, Rahman I, et al. Complex Visual Hallucinations in the Visually Impaired: the Charles Bonnet Syndrome. Survey of Ophthalmology. 2003:48(1):58-72.
  • (iv) Cox TM, ffytche DH. Negative outcome Charles Bonnet Syndrome. Br J of Opthalmol 2014;98:1236-1239.
  • (v) Levine AM. Visual hallucinations and cataracts. Opthalmic Surg. 1980;11:95-8.
  • (vi) Cogan DG. Visual hallucinations and release phenomena. Albrecht Von Graefes Arch Klin Exp Opthalmol. 1973;188:139-50.
  • (vii) Goldberg KB, Goldberg RE. Is seeing believing? Visual hallucinations in age-related macular degeneration and Charles Bonnet. J Ophthalmic Nurs Technol. 2000;19:39-42.