Vision is essential for driving. Good vision helps you identify road hazards, read signs and see your dashboard. Awareness of common vision-related changes and problems can help you and your loved ones stay safe while driving.
What kind of visual function is necessary for driving?
Visual acuity and field of vision (visual field) are the most important factors for safe driving. Vision regulations for driving vary from state to state, so check local laws to find out what your requirements are.
Visual acuity gauges how clearly you can see and is measured by reading letters on an eye chart. The test tells you whether you need glasses or contacts, or if your prescription needs to change.
Your visual field is how wide of an area your eye can see when you focus on a central point. There are different types of visual field tests. The one most commonly used in the United States is automated perimetry, in which you watch for flashing lights in a special device.
Additionally, color vision helps you identify traffic signals and brake lights. Contrast sensitivity helps you see pedestrians, lights and road signs in bad weather and at night.
Common vision changes that can affect driving
Normal, age-related eye changes can affect your vision and your ability to drive safely. These changes include presbyopia, which may impact your ability to see your dashboard or navigation system, and dry-eye, which can reduce the quality of your vision at night. Other conditions that can impact your driving vision include:
- Glaucoma, a disease that damages your eye’s optic nerve. Often, there are no warning signs or obvious symptoms in the early stages. As the disease progresses, blind spots develop in your peripheral vision, or, less commonly, in your central vision.
- Diabetic retinopathy, a disease in which high blood sugar levels cause damage to blood vessels in the retina, stealing both central and peripheral vision.
- Cataract, a progressive clouding of the natural lens inside the eye that causes blurry vision, glare and halos around lights. Cataracts can also make it harder to see well at night, in bad weather or in low light conditions. And they can gradually diminish color vision.
- Macular degeneration, a disease in which a part of the retina called the macula becomes damaged and causes loss of central vision.
For some people, these problems quickly become obvious. But for others they may cause a gradual loss of visual that’s less noticeable. Having regular eye exams can help your ophthalmologist find these changes early, and treat conditions promptly before they cause irreversible vision loss. The American Academy of Ophthalmology recommends regular eye exams by an ophthalmologist starting at age 40.
At night, lighting is poor and more complex visual tasks are required for safe driving. Be wary of devices that claim to improve night vision. Follow these tips to improve visibility while driving at night:
- Make sure your windshield and windows (inside and out), headlights and taillights are clean.
- Wear clean corrective glasses or contact lenses with an up-to-date prescription.
- Make sure your mirrors are always properly adjusted.
- Have your headlights properly maintained and replace broken bulbs promptly so they light the road adequately.
Red flags for driving safety
Regardless of your age, if you notice any of the following symptoms in yourself or a loved one, make an appointment with an ophthalmologist right away: