Who is Charles Bonnet?  He was a Swiss naturalist, philosopher, and biologist (1720-1793) who first described the hallucinatory experiences of his 89-year-old grandfather, who was nearly blind in both eyes from cataracts.   Charles Bonnet Syndrome is now the term used to describe simple or complex hallucinations in people who have impaired vision.  

Symptoms

People who experience these hallucinations know they aren't real.  These hallucinations are only visual, and they don't involve any other senses. These images can be simple patterns or more complex, like faces or cartoons.  They are more common in people who have retinal conditions that impair their vision, like macular degeneration, but they can occur with any condition that damages the visual pathway.  The prevalence of Charles Bonnet Syndrome among adults 65 years and older with significant vision loss is reported to be between 10% and 40%.  This condition is probably under reported because people may be worried about...

Alzheimer's Disease International estimates that the number of people living with dementia worldwide - nearly 44 million in 2014 - will almost double by 2030 and more than triple by 2050.

There is no single test that can show if a person has Alzheimer's, but doctors can almost always determine if a person has dementia, although it may be difficult to determine the exact cause. Diagnosing Alzheimer's requires careful medical evaluation, neurological testing, and sometimes brain imaging and blood tests to rule out other causes of dementia.

Most of the testing for early disease - MRI scans of the brain, brain PET scans looking for amyloid, and spinal taps looking for certain proteins in the spinal fluid - are not very accurate, and they are invasive and often expensive.

Researchers have now turned to findings in the eye to help with early detection and are hoping to find ways to make the diagnosis earlier when potential treatments may have a better outcome. There is also hope...