Found via Slashdot, an article on how images of the retina can be used to screen for common diseases, including heart disease and hypertension:

LiveScience.com – Window to the Heart: New Eye Exam Spots Disease Risk

Tien Wong of the Center for Eye Research Australia at the University of Melbourne has shown in several large-scale studies that abnormalities of the blood vessels in the retina can be used to predict patients’ risk for diabetes, hypertension (or high blood pressure), stroke and heart disease.

As the article notes but doesn’t focus on, this could become a major aspect of diagnosis and triaging, since retinal photographs are cheap, fast, and easy to acquire.