How does your vision affect your reaction time on the road?

Why is clear vision important for safe driving?

According to the Vision Impact Institute, more than 90% of a driver’s decisions depend on having good vision. Good eyesight can improve reaction time — the amount of time it takes to respond to a variety of circumstances, such as a vehicle ahead of you that makes a sudden stop.

“Good vision helps you identify road hazards, read signs and see your dashboard,” according to the American Academy of Ophthalmology.

Research indicates 23% of drivers experience a vision defect that can impact their ability to drive safely. For instance, a driver with poor vision might react slowly to a stop sign or an object blocking a roadway. That can put a driver, passengers, other motorists and pedestrians in harm’s way.

It doesn’t take long for a driver to run into trouble related to reaction time. For a highly trained driver, reaction time might be 0.2 seconds. But for an average driver, reaction time might rise to 0.5 seconds or even 1.5 seconds. Poor vision could make reaction time even worse.

The American Academy of Ophthalmology says the two most important factors related to vision and safe driving are:

• Visual acuity, which determines how clearly you can see. Clarity of vision is measured when an eye care professional asks you to read letters from an eye chart. Problems with visual acuity might lead to a heightened risk of auto accidents.
• Visual field, which is how wide an area your eyes can detect when you concentrate on one point. One way to test this is by watching flashing lights in a specialised eye care device.

What eye conditions can affect a driver’s reaction time?

Issues that might cause poor vision and reduce reaction time include:

• Myopia, or short-sightedness, a refraction error that can make it hard for a driver to read signs, perceive hazards, and see other road users and objects clearly from far away. 
• Presbyopia, or age-related long-sightedness, a condition that makes it difficult to see objects up-close, such as the map app on your smartphone and the electronics on your dashboard. 
• Macular degeneration, an incurable disease and the leading cause of vision loss in older individuals. The American Macular Degeneration Foundation explains that the central portion of the retina, known as the macula, is responsible for focusing central vision in the eye and controls your ability to drive.
• Glaucoma, a condition that damages the optic nerve of the eye. Glaucoma typically narrows the field of vision (weakening a person’s peripheral vision) and may cause blindness.
• Diabetic retinopathy, a condition that affects people with diabetes and can lead to vision loss or even blindness. The disease harms both central and peripheral vision.
• Cataracts, which cloud the natural lens inside the eye, and can result in blurred vision, dulled colours and increased light sensitivity.
• Dry eye, which can be caused by computer use, contact lens wear, allergies, air conditioning or medications, to name a few. Dry eye can lead to blurred vision, itchiness and eye fatigue, any of which can impair your vision, especially at night. 
• Blurred eyesight, which can be caused by drowsiness or dizziness associated with prescription or over-the-counter medications.

While clear vision is a priority for drivers of every age, vision problems represent one of the main reasons for older adults to cut back on driving or to quit altogether. 

Is it possible to drive safely without perfect vision?

There’s no way around it: You need regular eye exams to determine if your vision is fit for driving. This examination detects conditions that can affect your vision and possibly your reaction time on the road. 

While technology in vehicles has come a long way — going so far as to anticipate and react to drivers’ poor judgement — it is not a replacement for clear vision.

The good news: According to the World Health Organization, 80% of all visual impairments can be prevented, corrected or cured. So, whether you prefer to drive, bike or walk, seeing your optician for regular eye exams has the potential to keep your eyes healthy and your vision clear, making the roads safer for everyone.