When you go to renew your driver's license, you may have to take an eye exam, depending on how long it's been since you last visited the Dept. of Motor Vehicles, and depending on how old you are.

And that simple exam might conceal a major problem that many states apparently overlook. It keeps states from learning exactly how much difficulty many seniors have with seeing things at night.

According to Sean McKinney, a researcher for allaboutvision.com,
our pupils shrink and don't dilate as much in the dark as we age, reducing the amount of light entering the eye. Various reports indicate that the retina of an 80-year-old receives far less light than the retina of a 20-year-old. This can make older drivers function as though they are wearing dark sunglasses at night. How safe does that make you feel?

McKinney says the aging cornea and lens in the eye become less clear as we age, causing light to scatter inside the eye, which increases glare. These changes also reduce contrast sensitivity — the ability to discern subtle differences in brightness — making it harder to see objects on the roadway at night.

A older person may test well in the eye doctor's office but still struggle to focus on the road at night, where lighting is poor and more complex visual tasks are required.

According to the National Traffic Highway Safety Administration, advancing years decrease our ability to see stationary and moving objects, including cars or pedestrians that might cross the road in front of us. Our ability to resist glare and see reflective road signs and markings also decreases with age.

Many people's eyes have optical imperfections called higher-order aberrations that can't be corrected with eyeglasses or contact lenses. These aberrations increase with age and reduce vision, especially when the pupil dilates at night.

Shouldn't your state's Dept. of Transportation be aware of this?

Despite these ample reasons for concern, many states have lax vision screening requirements for drivers renewing their licenses.

According to a Vision Council report the 10 states with the highest rate of fatal crashes include four that require no vision screening for license renewal and four that only require screenings at intervals of eight or more years.

Perhaps it's time each state increases the frequency of vision testing for seniors? Wouldn't that be sensible?