• The science behind elderly drivers and aging eyes

    A beam of light travels to an eye that fills the frame, illustrating elderly drivers’ need for bright signs.

    Why is it crucial that we understand what happens to our eyes when we age?

    • The aging population in the U.S., as well as many other countries around the world, is growing at an exponential rate. Elderly drivers maintaining their drivers’ licenses and driving personal vehicles help to keep this population segment independent. However, this independence comes with an increased danger in having aging drivers on the road.

      According to the National Institute of Health, “The percentage of the population in the U.S. and many other countries over age 60 is increasing, and thus eye conditions, diseases, and vision impairments associated with aging represent a larger segment of our societal health challenge on a population basis than in previous decades.” 1 Older drivers need more visible road signs and pavement markings to help counter the eyesight degeneration and diseases that come with getting older. 2

    The science behind rods and cones

    • First, in order to understand how our eyes change when we age, it helps to grasp the basic workings of an eye functioning at its full capacity. Jane Brody of the NY Times states, “ in a normal healthy eye, light enters through the pupil and passes through the lens, which focuses it and directs it to the retina on the back of the eye, where images form.

      The retina contains two kinds of photoreceptors: cones and rods. Cones enable us to see when it is light. They give us color vision and allow us to see details like the words on this page. Rods are very sensitive, especially to motion. They provide only black-and-white images and thus are critically important for night vision.” 3

    Elderly drivers and changes in dark adaptation

    • A close-up of an iris reminds us that the eye changes as we grow older, needing more time to adapt to the intensity of light.

      So, what changes in your eye as you age that makes it more difficult to see in the dark?

      As you get older, the muscles in your iris that control the size of your pupil weaken and have trouble understanding how much light to let in. Aging eyes also begin to lose the rods that help them detect motion.

      Brody states, “In the young eye, rods outnumber cones by nine to one in the part of the retina called the macula. But an autopsy study of older adults found that while the cones remained intact, almost a third of the rods in the macula had been lost.” 3

      The result of these less receptive iris muscles is a slower adaptation to the intensity of light. This directly impacts a person’s ability to drive safely, as the eye is constantly working to adjust to changes of brightness on the road.

      “In older eyes, this phenomenon, called dark adaptation, takes longer, which means you see less well in the dark after being in the light, and vice versa. The diminished number of rods may be a factor, but in addition, the light-sensitive pigment in the rods regenerates more slowly in older eyes,” 3 according to Brody.


    Other age-related eye diseases & conditions

    • In addition to weakening eye muscles and loss of rods, many people experience other eye conditions associated with aging. Some of the most common are age-related macular degeneration, cataracts, and glaucoma.

    Age-related macular degeneration (AMD)

    • Age-related macular degeneration is a common eye condition and a leading cause of vision loss among people age 50 and older. It causes damage to the macula, a small spot near the center of the retina and the part of the eye needed for sharp, central vision, which lets us see objects that are straight ahead.4 As you can imagine, loss of central vision can be detrimental to an aging person’s ability to stay safe on the roads.


    • Another common condition in the aging population is the clouding of our optical lens, also known as cataracts. According to the National Eye Institute, the lens focuses light and adjusts the eye's focus, letting us see things clearly both up close and far away. The lens is made of mostly water and protein. The protein is arranged in a precise way that keeps the lens clear and lets light pass through it. 5

      “But as we age, some of the protein may clump together and start to cloud a small area of the lens. This is a cataract. Over time, the cataract may grow larger and cloud more of the lens, making it harder to see.”4 Because having a cloudy lens can scatter the light that is being directed to the retina, cataracts can often lead to glare in your vision that could cause temporary blindness.


    • Glaucoma (PDF, 183 KB) is a group of diseases that can damage the eye’s optic nerve and result in vision loss and blindness.6 Sometimes referred to as “blank spots,” these damages to the optic nerve will continue to grow and become more noticeable over time if not treated correctly. As the blank spots become more prevalent, the ability to see road signs safely decreases. Glaucoma is one of the leading causes of blindness in the United States, especially within the elderly community.6


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