A close look at our eyes could be all doctors need to get a glimpse at some serious problems.
"There's a lot of different things that the eyes can do that reflect general health," said retinal surgeon Dr. Allen Ho.
If your eyes have taken on a yellowish hue, you could be suffering from liver disease like hepatitis or cirrhosis.
Yellowish deposits on your lids could mean high cholesterol. A thin gray ring around the cornea can also mean high cholesterol, putting you at a higher risk for heart attack and stroke.
"The eyes are really an extension of the brain," said Ho.
Even eyes that are too white can be a problem.
"Because the hemoglobin levels are too low, because you've got low iron and you're anemic," said ophthalmologist Dr. Julia Haller.
Bulging eyes can run in the family, but they're also a sign of a thyroid problem known as Graves' Disease. Three-million Americans have it.
"[Former First Lady] Barbara Bush, for example, had problems with her thyroid eye disease," said Haller.
Have your eyelids suddenly started drooping? See your doctor right away: It could be an autoimmune disorder or even a brain tumor.
"We actually even diagnose diseases like AIDS sometimes. We're the ones that pick up that the patient has changes in the eye," said Haller.
"So getting a regular eye exam is really important even if you're seeing well," said Ho.
Even if you're not having vision problems, the American Academy of Ophthalmology recommends eye exams every two to four years for those older than 40. People over 65 should get screened every year or two.
But they say you should get checked out right away if you have any problems with loss of vision, pain or redness.