Seeing better can mean living longer because it helps people remain independent.

An eye exam may be the ticket to a longer life, researchers say, because good vision is essential for being able to shop, manage money and live independently. And maintaining independence in turn leads to a longer life.

Researchers have known for years that people who have vision problems as they get older are more likely to die sooner than those who still see well. But they weren't sure why that was so.

To answer that question, scientists looked at data from the Salisbury Eye Evaluation, which tracked the vision and health of people ages 65 to 84 living in Salisbury, Md., from 1993 through 2003.

People's visual problems at the start of the study or their loss of vision didn't directly predict an increased death risk, the researchers found. Instead, the vision loss made it less likely that people could pay their bills, do housework and otherwise manage their lives.

People who lost visual acuity equivalent to one letter on an eye chart each year had a 16 percent increase in mortality risk over eight years, and that was due to the loss in independent living abilities, the researchers said.

"An individual who's remaining relatively stable in their visual acuity in their older years is not seeing this subsequent difficulty in functionality," says Sharon Christ, an assistant professor of human development and family studies at Purdue University and the lead author of the study. It was published Thursday in JAMA Ophthalmology

The researchers did look at whether other factors, including physical illness, race, sex, depression, smoking, alcohol use and obesity, could be causing the increased mortality risk. But they found that the correlation between vision loss and instrumental activities of daily living was the strongest.

Reducing the risk may be as simple as getting an eye exam and new glasses or contact lenses, Christ told Shots. "It's really important to deal with impairment and make sure you're getting the eye care that you need."

People with vision problems that can't be corrected should get help with tasks of everyday life, Christ says, and be encouraged to remain physically active, postponing those functional declines for as long as possible.