Failing eyesight can quickly sideline your business. If you take care of your eyes, they’ll stay on the lookout a lot longer.

Your profession requires being able to see a great deal clearly: map details, distant road signs and peripheral activity in adjacent lanes. Every two years, you must pass your medical, which includes a vision exam. It’s easy to take good insight for granted, but for those approaching middle age, the days of perfect vision may be numbered.

Owner-operator Ron Snell says he realized his vision was getting worse when it became more difficult for him to read exit signs from far away. “I’d have to get up too close and not have time to react properly.” He then realized that he couldn’t read license plates in front of him and that he experienced some blurriness while driving at night. He has been wearing glasses ever since.

“As we get older, the ability of the eye to focus up close is slower and less efficient, and that is manifested as difficulty with reading,” says Dr. Janine Smith, deputy clinical director for the National Eye Institute. For example, you might have trouble trying to read the fine print in an atlas.

This condition, presbyopia, tends to show up between ages 40 and 50, Smith says. “A lot of people buy over-the-counter drugstore reading glasses,” Smith says. “This is fine as long as they see an eye care provider first and have their eyes examined to make sure that is what’s going on, because it could be something else.”

Reading glasses are simply magnifiers and are often adequate to treat presbyopia, says Dr. Daniel Coden, an ophthalmologist in La Jolla, Calif. Presbyopia worsens with age, so an exam every year or so is useful and often indicates that a prescription should be upgraded.