Even if the eye test proves effective in clinical trials, it's unlikely to replace blood sugar screening, the test most commonly used to detect diabetes. However, it may provide a useful early-warning tool. To detect prediabetes, physicians use the more sensitive glucose tolerance test, a time-consuming and expensive test in which blood glucose levels are monitored before and after a patient is given a sweet drink.

Petty hopes to make the eye imaging system inexpensive enough that it could be used by optometrists, not just ophthalmologists, to identify people who may have prediabetes. Glucose tolerance testing would confirm the diagnosis. "Hopefully, we can find out who these patients are and get them into the right treatment and care," Petty says.

Petty believes that the technology could motivate people to take better care of their health because "you can tell someone, 'You're sliding toward the edge of the cliff, and here's the data that says so.'"

Eye tests could also be used to monitor diabetic patients, Petty says, and assess the effects of drug treatments and lifestyle changes. Diabetics can lose "a substantial fraction--up to 50 percent--of their retinal cells" before they're aware of vision problems, Petty says, because the brain adjusts to the input from the eyes--up to a certain point. "Once you're beyond that threshold, right now . . . you really can't get [vision] back," he adds.

Petty and his colleagues are now having a much smaller version of their first eye imaging system built. It will be easier to use, and unlike the current version, it won't require a patient's eyes to be dilated. Petty and Elner have filed for patents and formed a company, OcuSciences, to commercialize the technology.

"The application for diabetes is really staggering when you think about it," Petty says, "because there are so many diabetics and prediabetics in this country."