Charles Bonnet Syndrome - Causes, Symptoms, Diagnosis, and Management

Introduction

Charles Bonnet syndrome (CBS) is a visual condition characterized by a sudden loss of vision followed by the onset of visual hallucinations. The delusions occurring in patients are not psychological and not severe. Instead, they are primarily the effect of diminishing eyesight.

What Is the Human Visual Pathway?

The human visual pathway comprises the eye lens, cornea, retina, nerve fibers, and visual cortex (the region associated with seeing) in the brain. The visual sensations from the retina are transferred to the brain by sensory nerve fibers. The brain plays a vital role in forming and storing images.

Who Is More at Risk of Acquiring Charles Bonnet Syndrome?

Charles Bonnet syndrome mainly affects the elderly. However, young people with vision loss may also suffer from delusions. Even though there is no clear distinction about the gender most affected by the disease, Females are postulated to be more prone to acquiring Charles Bonnet syndrome.

What Is the Main Causative Factor Responsible for Charles Bonnet Syndrome?

Charles Bonnet syndrome is caused mainly because of the defective visual pathway. The brain compensates for the lack of images or signals from the eye by forming delusional photos from the already stored ones.

What Is the Mechanism Behind the Formation of Delusional Images in Charles Bonnet Syndrome?

The exact mechanism behind the development of Charles Bonnet syndrome remains challenging to elucidate till now. However, many theories have been postulated regarding Charles Bonnet syndrome.

• The most accepted theory is the deafferentation theory. Deafferentation is the destruction of the sensory nerves carrying the messages from the body to the brain.

• According to the deafferentation theory, lesions in the visual pathway lead to the destruction of the sensory nerve fibers responsible for carrying messages from the eye to the brain. In addition, the deafferentation causes disturbances in the visual cortex (area of the brain which sends and receives signals from the eye). All these changes culminate into visual hallucinations.

What Are the Risk Factors That Contribute to the Formation of Charles Bonnet Syndrome?

Charles Bonnet syndrome is associated with several factors that contribute to the initiation and progression of the disease.

The risk factors include:

• Degeneration of the macula.

• The presence of other ocular impairments -

• Cataracts.

• Severe shortsightedness (myopia).

• Glaucoma.

• Diabetic retinopathy.

• Ocular diseases are caused by defective vessels supplying the retina, such as retinal vein blockage (occlusion), damage to the retinal vessels due to inadequate blood supply (retinal infarction), and central artery occlusion.

• Ocular surgical procedures.

• Social isolation.

• Decrease in cognition (capacity of a person to comprehend information).

What Are the Different Forms of Charles Bonnet Syndrome?

Charles Bonnet syndrome occurs in many forms clinically.

• Firstly, based on the type of hallucinations, it is of two types:

  • Simple hallucinations.

  • Complex hallucinations.

• Secondly, based on the frequency of hallucinations, it is of three types:

  • Episodic hallucinations.

  • Periodic hallucinations.

  • Continuous hallucinations.

What Are the Clinical Signs and Symptoms of Charles Bonnet Syndrome?

Charles Bonnet syndrome affects both eyes. It produces various clinical presentations.

• Patients getting simple hallucinations experience flashes of light or simple shapes and patterns with vivid colors. However, patients suffering from complex types hallucinate complex structures like people, animals, plants, etc., that may be moving or stationary. They find it challenging to get around due to the disorientation about the distance between the objects.

• The visions seen by the patient mostly are not frightening or distressing. In addition, in some patients, the delusions are triggered by fatigue, bright light, and stress.

• The delusions may last for a few hours or days. The delusional episodes might occur and linger for a few days, then resolve without any other episode (episodic). Some of the hallucinations have a recurrent pattern (periodic) or may be continuous.

How Are Patients With Charles Bonnet Syndrome Diagnosed?

Charles Bonnet syndrome lacks a definite diagnostic procedure. Instead, doctors conclude the condition by acquiring complete medical and drug history from the patients. Psychological tests rule out severe mental illnesses like dementia and Alzheimer's.

What Are the Various Approaches Used in Treating Patients With Charles Bonnet Syndrome?

Charles Bonnet syndrome does not have a specific treatment strategy. Sometimes, the hallucinations resolve by themselves. However, other underlying causes of Charles Bonnet syndrome are to be solved.

• No medications help in stopping hallucinations occurring in Charles Bonnet syndrome. However, for patients with severe anxiety or fear, antipsychotic drugs are prescribed. Unfortunately, the side effects of the medicines outrun their benefits, hence should be used with caution.

• People are reassured about the non-serious nature of hallucinations and made familiar with their surroundings.

• People are encouraged to adopt self-help measures such as:

• Restful sleep and relaxation.

• Low vision practice. In addition, they are motivated to reach out to their physicians, family members, and friends about their problems.

• Patients are advised to go for a regular eye checkup and avoid sudden changes in the lighting.

Eye exercises such as -

• Eye movements in all directions.

• Rapid blinking of the eyes while staring long at objects. These measures help in improving the symptoms in some patients and

• Avoid stressful conditions that aggravate the disease.

What Are the Complications Linked to Charles Bonnet Syndrome?

Charles Bonnet syndrome, as such, does not cause any severe complications. However, patients suffering from the disease often suffer from anxiety, fear, and depression.

Research linking Charles Bonnet syndrome with the increase in mortality rate and dementia is present. However, there is a lack of substantiating evidence.

What Are the Conditions That Mimic Charles Bonnet Syndrome?

Persistent hallucinations present in Charles Bonnet syndrome of the elderly need to be distinguished from other diseases.

Other conditions with similar manifestations are:

• Neurologic disorders.

• Psychological disorders.

What Is the Overall Outlook of Charles Bonnet Syndrome?

There is no cure for the disease at present. Hallucinations might resolve by themselves sometimes. Hallucinations seen are not frightening.

Conclusion

Charles Bonnet syndrome is a rare ocular disease. The under-reporting and lack of awareness of the disease entity diminish the patient's quality of life. Therefore, proper diagnosis of the condition followed by patient reassurance remains the mainstay of treatment.