They say that your eyes are windows to your soul.

And regardless of whether that's true, there sure is a lot that docs can tell about your health by peering deeply into them.

Of course, eye diseases like glaucoma and macular degeneration can steal your sight, but that's not all that your doc can see in an eye exam.

The health of the nerve cells and tiny blood vessels in the back of your eyes (a.k.a. your "retina") are a reflection of what's going on elsewhere in your body. Early signs of heart disease... diabetes... and even cancerous tumors often show up in your eyes.

And now, a new study shows that your eyes may also be a window to your BRAIN -- because certain changes in the retinas may be a sign of Alzheimer's.

In the study, when UK researchers scanned the eyes of about 120 older folks, they found that 25 percent of those with Alzheimer's had yellow spots called "hard drusen" on their retinas, compared to just 4 percent of the control subjects.

Now, the "hard" type of drusen has long been considered harmless, because it rarely impairs your vision (unlike the "soft" type, which increases the risk of macular degeneration ).

But we know that hard drusen -- abnormal deposits of fat and calcium -- are associated with oxidative stress , and oxidative stress has also been linked to the development of Alzheimer's.

What's more, the study found that those with Alzheimer's had THICKER blood vessels in the backs of their eyes than the controls.

As I've shared with you before, when your blood vessels thicken, it restricts the amount of blood that can flow through.

And we know that when blood can't gush freely to your eyes, it likely also can't gush freely to your BRAIN -- and that kind of "plumbing problem" is a risk factor for Alzheimer's.

Of course, it takes more than an eye exam to diagnose Alzheimer's. It’s likely not caused by any one thing (and as I shared with you yesterday, it looks as though a viral infection may play some role), and it won’t manifest in just one way.

But this new study is a good reminder to get your eyes checked out regularly -- not only to screen for eye diseases but also to gain "insight" into your general health.

And it just so happens that many of the same healthy habits that protect your eyes from disease also help shield your brain from dementia.

Eating leafy greens like kale, collards, and spinach can slash your risk of glaucoma AND dementia because they're loaded with nitrate, which your body converts to a compound called nitric oxide (NO) that boosts blood flow.

Leafy greens are also packed with antioxidants that ease oxidative stress.

And lay off "white carbs" like sugar and flour -- because having high blood sugar ups your risk of not only macular degeneration and diabetic retinopathy, but also Alzheimer's.