Preliminary tests have found a striking relationship between these small changes and existing eye damage. Under the leadership of optometry professor Anthony Adams, the school has now launched a $1.6 million research project to study these changes in people with diabetes.

Subjects are being recruited who have the disease but little evidence yet of eye complications, said Adams, who will complete in August a nine-year term as dean of the school. Some 44 patients have already been enrolled; researchers would like to enroll 100 or more adults under the age of 65 with good vision.

They will be followed for four years with the most advanced techniques for measuring the health of the retina. Those who develop eye problems will be referred for eye care that could prevent severe vision loss.

Eye complications caused by diabetes are the leading cause of blindness in the United States among adults ages 25-74.

The changes being studied are tiny alterations in the electrical signals detected from patches of the retina, which contains cells that transfer information from the eye's cones to the brain. Declines in the size and speed of those tiny signals correlate with eye complications in diabetics, said Adams, whose research team first noted this in the retinas of eight patients two years ago.

To the surprise of the researchers, they also discovered tiny alternations in some patches of retina where no eye complications were seen.

"We need to find out if these changes develop into a condition called 'diabetic retinopathy'," said Adams. "We need enough patients to know that our preliminary findings are not a fluke."

He said it is hoped the study will pinpoint those places in the back of the eye that develop "retinal edema," leakage of fluid into the retina, a leading cause of vision loss, and "capillary dropout" where tiny blood vessels that supply oxygen and nutrients to the eye collapse.

Laser treatment, if applied early enough, can slow the progression of the disease. Good control of blood sugar levels through medication, diet and exercise can significantly slow or minimize it, said researcher Marilyn Schneck, a principal investigator on the UC Berkeley study.

Even then, a significant number of diabetics may lose vision despite their best efforts, said Schneck.

Subjects in the study are brought to a room in the optometry school called "the Sugar Shack." There Schneck has studied the relationship between sugar levels and eye responses for the last 14 years. For this study she applies a technique called the "multifocal electroretinogram" (M-ERG) that can detect tiny electrical signals from specific areas of the retina and display them in colorful computer graphics highlighting the retinal changes.

Information on how to participate in the diabetes study