Hallucination vs. Illusion:
- Hallucination is sensory perception of things that are not there and persist with eye closure.
- Illusion is misperception of viewed objects.
What is Charles Bonnet Syndrome (CBS)?
- CBS is classified under hallucination and may occur in patients with visual acuity loss, visual field loss or reduced contrast sensitivity (1, 2).
- It may also occur in patients with relatively good vision, but have increased emotional distress and decreased quality of life (3).
- Patients with CBS see images that include complex colored patterns, but know that the images are NOT real.
- Images of people are most common, followed by animals, plants or trees and inanimate objects (5).
- Images are often pleasant and do not scare patients.
- These hallucinations are only visual and not occur with other senses, e.g. hearing, smell or taste.
- Some people experience CBS for anywhere from a few days up to many years, and these hallucinations can last from seconds to most of the day.
- CBS is often described as similar to “the phantom limb” where patients with limb amputation still feel the sensation that the missing limb is attached to the body (3).
Pathophysiology:
- One theory of CBS is the release theory where sensory deprivation leads to the release of subconscious perceptions.
- Any pathology affecting the visual pathway (retina, optic nerve, brain) can lead to CBS.
- Common conditions causing CBS are (1,4): age-related macular degeneration, glaucoma & cataract.
Incidence:
- 11%-15% of people with vision loss (3).
- Mean age of incidence is 75-80 years old.
- Impaired vision is usually 20/60 or worse in the better eye.
Management:
- CBS is arrived via diagnosis of exclusion.
- We must rule out neurologic, psychiatric, metabolic and other toxic disorders.
- It is important to carefully review the patient’s prescription medications and ask about the use of any illicit drugs.
- Though there is no treatment for CBS, it is vital to educate and reassure patients of their condition.
- Referral to patient’s PCP and neurologist for appropriate work-up.
Tips for Patients with CBS:
- Closing or blinking eyes may alleviate hallucinations (5).
- Additional lighting, encouraging patients to stay physically and mentally active and participating in social activities can reduce the frequency and vividness of the images (6).
References:
1. Jacob A, Prasad S, Boggild M, Chandratre S. Charles Bonnet syndrome–elderly people and visual hallucinations. BMJ 2004; 328:1552.
2. Jackson ML, Bassett K, Nirmalan PV, et al. Contrast sensitivity and visual hallucinations in patients referred to a low vision rehabilitation clinic. Br J Ophthalmol. 2007;91:296–8.
3. Scott IU, Schein OD, Feuer WJ, Folstein MF. Visual hallucinations in patients with retinal disease. Am J Ophthalmol. 2001; 131 (5): 590
4. UpToDate. Visual release hallucinations (Charles Bonnet Syndrome). Obtained on [April 28, 2013]
5. Vukicevic M, Fitzmaurice K (2008) “Butterflies and black lacy patterns: the prevalence and characteristics of Charles Bonnet hallucinations in an Australian population”. Clinical and Experimental Ophthalmology. 36:659-65
6. The Lighthouse Clinicians’ Guide to Low Vision Practice
