Millions of Americans need glasses to help them see. However, a growing number of American adults, including Jerry Fishman, have vision loss that glasses can't correct.

“It was becoming almost impossible for me to see anything clearly,” Fishman said.

He was diagnosed with diabetes and diabetic retinopathy – and he's not alone.

"In working-age Americans, it’s diabetic eye disease that is a predominant cause of retinal disease," said Dr. David S. Friedman of Johns Hopkins School of Medicine.

Researchers looked at data from people participating in the National Health and Nutrition Examination Survey. Those living below the poverty line had almost twice the rate of vision loss as others.

Education and insurance status also play a role.

“The only major risk factor for vision loss that increased over time was diabetes lasting 10 or more years,” Friedman said. “The prevalence of diabetes is increasing, and people are having it longer because they are having it at a younger age."

The study, published in the Journal of the American Medical Association, also showed that uncorrectable vision loss increased by 20 percent over the study period. Among those 20 to 40 years of age, it increased by 40 percent.

“If we continue at the pace that we're going, we're going to see a lot of working-age Americans with vision loss related to diabetes," Friedman said.

After Fishman was diagnosed, he changed his diet and lifestyle. And he’s making great progress.

"I've made my mind up that it's going to get better,” he said.