Causes of Charles Bonnet Syndrome
Causes of Charles Bonnet syndrome are related to significant vision loss, which disrupts normal communication between the eyes and the brain. When the brain receives fewer signals from the eyes, it may begin to “fill in the blanks” by generating images on its own. This leads to the vivid hallucinations that define Charles Bonnet syndrome.
1. Visual Deprivation
The primary trigger is visual deprivation. When the brain’s visual cortex isn’t stimulated due to loss of sight, it becomes hyperactive and may begin to create its own images. This phenomenon is similar to the way the brain compensates in phantom limb syndrome by creating the illusion of sensation in an amputated limb.
2. Eye Conditions That Lead to Vision Loss
Several eye conditions are linked to Charles Bonnet syndrome, including:
- Age-related macular degeneration (AMD) – the most common cause, especially in older adults
- Glaucoma – damages the optic nerve, leading to vision loss
- Diabetic retinopathy – caused by damage to the retina from high blood sugar
- Cataracts – cloud the lens of the eye, reducing visual clarity
- Retinal detachment or optic neuritis
While not everyone with these conditions develops hallucinations, those with severe vision loss are more at risk.
3. Sudden or Progressive Vision Loss | Causes of Charles Bonnet Syndrome
Charles Bonnet syndrome may develop after both sudden and gradual vision loss. Some people experience hallucinations shortly after losing sight, while others notice them years later. The exact threshold of vision loss required to trigger the condition is unclear, but most individuals retain some limited vision.
4. Brain Response to Sensory Loss
Research shows that the visual cortex remains active even when not receiving input. In the absence of real images, it may create visual hallucinations using stored memories or creative processes. This activity is involuntary and has no link to mental health problems.
5. Age and Cognitive Awareness
Older adults are more likely to experience Charles Bonnet syndrome, particularly those over 70. It is also more common in people who are cognitively intact — that is, they are mentally healthy and aware that the hallucinations aren’t real.
Understanding the causes of Charles Bonnet syndrome helps remove the stigma often associated with hallucinations and reassures patients that the condition is neurological rather than psychiatric.
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