Charles Bonnet Syndrome (CBS), a rare visual condition, is now becoming increasingly common with the increase in cases of eye disorders, globally, doctors say. In 1760, Swiss philosopher Charles Bonnet identified and described this phenomenon after observing his own grandfather who lost his vision from cataracts. The condition is colloquially known as “phantom vision” as it causes hallucinations.
What is Charles Bonnet syndrome?
Charles Bonnet Syndrome or CBS is a condition where individuals with partial or complete vision impairment experience accompanied by complex and vivid visual hallucinations, even though they are psychologically healthy. Experts say that it is a neuro-ophthalmological condition where a person may see various visions, without the presence of other underlying psychological issues.
Estimate from one large study indicate that the overall prevalence of CBS is 0.5% (5/1000). Of these, 0.8% (1/120) of cases were in those with low visual acuity in the study sample, 0.6% (2/346) in the elderly, and 0.8% (1/120) in both the elderly and those with low visual acuity.
People of all ages can be susceptible to CBS, but older people are at a higher risk. The mean age of those affected is generally between 70 and 85. However, it is important to note that children with a high rate of rapid visual loss have also been documented to have CBS.
What are the symptoms of CBS?
People suffering from CBS see various visual elements and hallucinations. Medical research and case studies indicate that people may see patterns, shapes, dots, lines, people, animals, objects, landscapes, and more. The ‘visions’ can be either static or moving, have colours or be black and white. There have also been reports of patients seeing imaginary creatures or objects. These ‘visions’ can sometimes last for minutes or even continue for hours.
The hallucinations are notably only visual, and patients do not hear any sounds or feel things in their other sensory organs unlike in other mental health issues, where persons may also experience other sensory elements along with visual elements.
Why does CBS occur?
Research indicates that when people start to lose their vision due to age-related macular degeneration, glaucoma, or other visual disorders, their visual system fails to create new images. When there are limited or no new images coming in through the natural visual system of the body, the human brain starts to fill the void by creating its own images or recalls older images. That is what is believed to cause visionary hallucinations. This is akin to people who have lost a limb sometimes feel phantom pain. Having the condition is not a sign of a mental health problem.
Ruby Misra, ophthalmologist at Disha Eye Hospitals, West Bengal, said that the condition may occur in patients due to damage to their visual pathway. “There are various theories explaining the occurrence of CBS, but the main hypothesis is ‛Deafferentation Theory’ which suggests that the hallucinations are due to increased activity in the occipital cortex due to reduced sensory input in the eye. Common causes include macular degeneration, glaucoma, cataract, retinitis pigmentosa, high myopia, cerebral infarctions, diabetic retinopathy and venous occlusion,” she said. Dr. Misra added that she saw 2-3 cases of CBS annually.
What is the diagnosis and treatment?
CBS can remain undiagnosed for years, as there are no specific tests for this condition. Since it is characterised mostly through visual hallucinations without the delusions attached to it and the absence of hallucinations in other sensory modalities, a healthcare/eye care specialist usually takes the patient’s medical history, following which an ophthalmologist and neurologist may conduct certain physical and eye examinations to rule out possibilities of other diseases that can cause similar hallucinations.
There is no known cure for CBS to date, but there are some techniques that ophthalmologists suggest to help control the symptoms. Management depends on how much the hallucinations are affecting a patient’s day to day life. Patients need to be reassured about their symptoms and their mental health. Behavioural techniques include blinking during a hallucination or moving the eye rapidly from one object to another, away from field of vision in which the hallucination is seen.
Symptoms may disappear over time, but it may take several years for that to happen.
Medications to address the disease directly have proven to be partially effective. In some cases, antidepressants or anti-anxiety medications are used to deal with the distressing, negative impacts this syndrome may have on a person’s mental health.
