Most U.S. states require a visual acuity of at least 20/40 in your better eye to qualify for a standard driver’s license. That means you need to see at 20 feet what a person with normal vision sees at 40 feet. You can meet this standard with glasses or contact lenses, and if you do, your license will carry a corrective lens restriction requiring you to wear them every time you drive.
What 20/40 Vision Means in Practice
Visual acuity is measured using a Snellen eye chart, the familiar poster with rows of shrinking letters. A score of 20/40 means you need to be 20 feet away to read what someone with perfect 20/20 vision can read from 40 feet. It’s a moderate reduction in sharpness, roughly the point where road signs become harder to read at highway speeds and pedestrians are tougher to spot in cluttered environments.
All but three states have drawn the line at 20/40 for a standard, unrestricted license. Georgia allows up to 20/60, while New Jersey and Wyoming set their cutoff at 20/50. These numbers always refer to your best corrected acuity, meaning the result you get while wearing your glasses or contacts, not your naked-eye score.
Peripheral Vision and Color Recognition
Sharpness isn’t the only thing that matters. Many states also test your horizontal field of vision, which is your ability to detect objects off to the side without turning your head. For commercial drivers, the federal standard is at least 70 degrees in each eye, giving a combined field wide enough to monitor mirrors, lane changes, and intersections. States vary in how strictly they enforce peripheral standards for regular licenses, but a significantly narrowed field of vision can trigger restrictions or denial.
Color recognition rarely comes up for non-commercial drivers. Standard traffic signals use a fixed top-to-bottom order (red, yellow, green), so most people with color blindness navigate them without difficulty. Commercial drivers face stricter rules. Federal regulations require the ability to distinguish standard red, green, and amber, and some states apply the same requirement to school bus endorsements. A person who cannot recognize signal colors will be denied a commercial license under federal motor carrier standards.
Commercial Driver Requirements
If you’re applying for a commercial driver’s license (CDL), the bar is higher. The Federal Motor Carrier Safety Administration requires 20/40 acuity in each eye individually, not just your better eye. You also need 20/40 binocular acuity (both eyes working together), at least 70 degrees of horizontal field in each eye, and the ability to identify traffic signal colors. These standards apply whether or not you wear corrective lenses.
Drivers who don’t meet these thresholds can apply for a federal vision waiver, but the process involves additional medical documentation and monitoring. The waiver program exists primarily for drivers who have lost vision in one eye or have other stable conditions that fall just below the standard.
Driving With One Eye
Having vision in only one eye does not automatically disqualify you from getting a regular license. Most states will issue a license to a monocular driver as long as the functioning eye meets the acuity standard, typically 20/40. Pennsylvania, for example, allows monocular drivers to hold a license provided their combined vision (effectively their one good eye) reaches 20/40, with a recommendation from an eye doctor if the weaker eye can’t be corrected.
The main concern with monocular vision is reduced depth perception and a narrower total field of view. Some states add restrictions like side-mirror requirements or limit driving to daylight hours. Commercial licensing is more restrictive: federal rules generally do not permit monocular drivers to operate large trucks or buses without a waiver.
Bioptic Telescopic Lenses
For people whose acuity falls below the standard even with regular glasses, miniature telescopes mounted on eyeglass lenses, called bioptic telescopic lenses, can sometimes bridge the gap. These devices let you glance briefly through a magnified view for tasks like reading signs, while using your regular peripheral vision for general driving.
Not every state permits bioptic driving, and those that do impose specific requirements. In Pennsylvania, bioptic drivers must demonstrate at least 120 degrees of horizontal visual field, own the lens system for a minimum of three months before testing, and complete an evaluation with a certified driving rehabilitation specialist. If acuity through the bioptics is worse than 20/50, driving is restricted to daylight hours only. Drivers who achieve better than 20/40 through their bioptics can apply for nighttime privileges after one year with a clean driving record.
The Corrective Lens Restriction
If you pass the vision screening only while wearing glasses or contacts, your license will carry a restriction code (the specific letter or number varies by state). In Alaska, for instance, it’s Restriction Code 1. This means you are legally required to wear your corrective lenses any time you operate a vehicle. Driving without them is a citable offense, similar to driving without a valid license, and could affect your insurance if you’re involved in a crash.
You don’t need a doctor’s visit to have this restriction added. If you show up to the DMV and can only read the chart with your glasses on, the restriction goes on your license automatically. Removing it later requires demonstrating that your uncorrected vision now meets the 20/40 threshold, either at the DMV or through an optometrist’s exam.
Age-Related Screening and Renewal
Your eyes change over time, and most states build vision re-screening into the license renewal process. The frequency and format vary widely. Some states require an in-person vision test at every renewal, others only after a certain age, and a few allow online renewal with no vision check at all for younger drivers.
Age-related vision changes tend to accelerate after 40 and again after 65. The American Academy of Ophthalmology recommends comprehensive eye exams every two to four years for adults aged 40 to 54, every one to three years for those 55 to 64, and every one to two years after 65. These intervals are more frequent than most license renewal cycles, so it’s possible to develop a vision problem between renewals without the DMV catching it. If you notice your night vision worsening, halos around headlights increasing, or road signs getting harder to read, getting an eye exam before your renewal date is worth doing.
How the UK Standard Differs
Outside the United States, vision requirements take different forms. In the UK, the standard driving test asks you to read a number plate from 20.5 meters (about 67 feet) in good daylight. This roughly corresponds to a Snellen acuity of around 6/12, which is the metric equivalent of 20/40. Research published in the British Journal of Ophthalmology found that even among people whose clinical acuity fell in the expected passing range, only about 92% could read all test plates at the legal distance, and 3.3% couldn’t read any of them. The inconsistency highlights a limitation of real-world vision screening compared to controlled eye chart testing.