I was intrigued to hear about an experimental test to detect signs of Alzheimer’s disease by imaging the retina at the back of the eye. Researchers have found, at least in mice, that beta amyloid plaques can be detected in the retina before they gunk up the brain and interfere with memory and other mental functions. Whether the imaging will prove useful in humans remains to be seen.

But ophthalmologists already get a window into our health by examining the blood vessels, nerves, and structures of the eye because all the body’s systems are interconnected. Here’s what they frequently spot: