Charles Bonnet Syndrome (CBS)

Charles Bonnet syndrome (CBS) is a condition in which people with vision loss experience visual hallucinations. These hallucinations are caused by reduced visual input to the brain and are not a sign of mental illness, dementia, or psychiatric disease.

People with CBS understand that the images they see are not real. The hallucinations can range from simple shapes or patterns to detailed images of people, animals, faces, or scenes.

CBS most often occurs in individuals with significant vision loss from eye diseases such as macular degeneration, diabetic retinopathy, glaucoma, or retinal vein occlusion.

CBS develops when the brain receives less visual information because of reduced vision. In response, the visual centers of the brain may create images on their own, leading to visual hallucinations.

This process is sometimes compared to “phantom limb” sensations after an amputation, where the brain continues to perceive sensations despite reduced input.

CBS is associated with many eye conditions that reduce vision, including:

• Age-related macular degeneration (AMD)
• Diabetic retinopathy
• Glaucoma
• Retinal vein occlusions
• Cataracts
• Retinitis pigmentosa
• Stroke affecting vision pathways

The hallucinations are not caused by psychiatric disease, and patients typically remain fully aware that the images are not real.

Visual hallucinations in CBS vary widely between individuals.

Patients may see:

• Patterns or geometric shapes
• Faces or people
• Animals or insects
• Landscapes or buildings
• Moving figures
• Bright colors or flashing images

The hallucinations may:

• Last seconds to hours
• Occur daily or occasionally
• Appear suddenly
• Happen more often in dim lighting or quiet environments

Importantly, patients with CBS do not usually hear voices or experience confusion associated with psychiatric illness.

CBS is more common in:

• Adults over age 65
• Patients with moderate to severe vision loss
• Individuals with central vision impairment
• Patients who are socially isolated

CBS may be underdiagnosed because many patients hesitate to mention hallucinations due to fear of being misunderstood.

There is no single test for CBS. Diagnosis is based on:

• The presence of vision loss
• Visual hallucinations
• Awareness that the hallucinations are not real
• Absence of other neurologic or psychiatric symptoms

A retinal specialist or eye doctor may identify underlying eye disease contributing to reduced vision.

Sometimes additional evaluation by a neurologist or primary care physician may be needed to rule out other causes of hallucinations.

CBS itself is not dangerous and does not mean someone is developing dementia or mental illness.

However, hallucinations can sometimes be upsetting or frightening, especially if patients are unaware of the condition.

Education and reassurance are extremely important because understanding the condition often reduces anxiety.

There is no specific cure for Charles Bonnet syndrome, but symptoms often improve over time.

Treatment focuses on:

• Improving vision when possible
• Managing underlying eye disease
• Reducing anxiety about hallucinations

Helpful strategies may include:

• Increasing lighting
• Blinking or moving the eyes
• Looking away from the hallucination
• Staying socially engaged
• Reducing stress and fatigue

Some patients notice hallucinations occur more frequently during periods of isolation or low stimulation.

Can Better Vision Help?

In some cases, improving vision through treatment of cataracts or retinal disease may reduce hallucinations.

Management of underlying eye conditions is important whenever possible.

Many patients feel relieved after learning that CBS is a recognized medical condition and not a psychiatric disorder.

Helpful tips include:

• Talking openly with your doctor
• Sharing symptoms with family members
• Maintaining social interaction
• Keeping regular eye appointments
• Managing stress and fatigue

Support groups and low vision specialists may also be helpful.