For years, Barbara Alpan relied on her daughter, Lara, for rides, but not anymore. She was diabetic in her 30s, and it eventually took a toll on her eyes.

“If I was driving and somebody came up on the left, I wouldn't have seen them," said Alpan, now 63.

Dr. Rithwick Rajagopal, an ophthalmologist at Washington University School of Medicine in St. Louis, is an expert in diabetes-related vision loss.

"Currently, diabetic retinopathy is diagnosed and treated at the late stages of the disease," Rajagopal said.

For years, doctors have blamed vision loss on blood vessel damage around the retina, but new research shows eye injury may begin much earlier in nerve cells.

Rajagopal and his colleagues fed mice a high-fat diet, giving them diabetes and then diabetic retinopathy. At six months, the mice showed signs of nerve problems.

"We could detect subtle issues in vision prior to the animals developing issues with retinal blood vessels," Rajagopal detailed.

Researchers did not see actual blood vessel damage in the mice until 12 months. Rajagopal said this finding could lead to earlier diagnosis.

"Eye tests, for example, that might be able to tell us this person is at high-risk of developing diabetic retinopathy, while this other person might not be," Rajagopal said.

That could lead to early treatments. Doctors say Alpan was an exception. Surgery restored her eyesight, despite advanced disease.

"It's had a huge impact on her well-being," said Alpan's daughter, Lara said.

Also on her confidence behind the wheel.

Researchers say other studies indicate people with diabetes go through a phase that seems to be similar to the early nerve damage that Washington University researchers found in mice. Doctors say it could be several years before new therapies could be developed to stop or reverse the nerve damage.

DOWNLOAD and VIEW research summary and an in-depth interview with the doctor