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 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.

Vision loss can adversely affect the ability of older adults to perform instrumental activities of daily living (IADL), such as using the telephone, shopping and doing housework, which are all measures of an individual's ability to live independently, and that subsequently increases the risk for death.

Visual impairment (VI) also can have negative effects on a person's physical and psychosocial health. VI is associated with a variety of functional and health outcomes.Declines in VA acuity over time were associated with increased mortality risk in part because of decreasing levels of IADL over time. Individuals who experienced increasing difficulty with IADL had an increase in mortality risk that was 3 percent greater annually and 31 percent greater during the 8-year study period than individuals with a stable IADL difficulty level. Participants who experienced the decline in VA of one letter on an acuity chart were expected to have a 16 percent increase in mortality risk during the 8-year study because of associated declines in IADL levels.

"Our findings have multiple implications. First, these findings reinforce the need for the primary prevention of VI. …Moreover, the early detection of disabling eye diseases is suboptimal in the U.S. health care system, leading to otherwise preventable VI. Finally, many Americans live with VI that is correctable through the proper fitting of glasses or contact lenses. A second implication of our findings suggests that when uncorrectable VI is present, helping affected individuals maintain robust IADL is important." Sharon L. Christ, Ph.D., of Purdue University, West Lafayette, Ind., and colleagues wrote in theirJAMA Ophthalmology paper, which was published on-line this week.