Vision and driving

Why is good vision necessary for driving?

Good vision is essential to the safe operation of any motor vehicle. It has been estimated that 90% of the sensory information required for driving is visual. A driver with reduced vision may take longer to perceive and react to a hazard ahead, or even fail to see another vehicle or pedestrian, especially in demanding conditions such as rain, highway speeds, or night driving.

What standard of vision is required to hold a drivers licence?

In most states of Australia, the driver of a car, motorcycle or light truck needs to have visual acuity of 6/12 (also referred to as 20/40) with both eyes open (see 'What is 20/20 vision' for an explanation). The driver also needs to have satisfactory peripheral vision.

In addition to these standards, some less common conditions, such as double vision, eye patching, sudden loss of vision in one eye, and glaucoma, can also affect driving. Your optometrist can provide further advice.

What about commercial drivers licences (e.g. truck, bus, taxi)?

In Australia, commercial drivers must pass a stricter visual standard. Each eye is tested separately, and at least one eye must have 6/9 vision or better. The other (weaker) eye must have 6/18 vision or better. Commercial drivers must have complete peripheral vision.

There is also a colour vision requirement for commercial drivers. Some studies have suggested that drivers with certain types of colour vision deficiency are more likely to be involved in a rear-end collision. These drivers are excluded from holding a commercial drivers licence.

Does deteriorating vision with age affect driving?

The effects of ageing on vision are well known and include:

• Difficulty seeing at night or in poor light
• Glare, whether from headlights at night, or from the sun, becomes more troublesome
• Colour vision may diminish
• Changing focus to different distances becomes slower

The formation of any cataracts intensifies the above problems.

Evidence suggests that if older drivers are prepared to compensate for ageing eyesight by adjusting their driving habits, then deteriorating vision is not necessarily a barrier to safe driving. Changing habits may include:

• Driving only in daylight or on well-lit roads
• Driving only in fine weather
• Driving only in the familiar local area

How do I know whether I will meet the standard?

An eye examination with an optometrist is easily arranged, and will provide you with a full assessment of whether your vision meets the legal standards before actually applying for your licence. If you need a commercial drivers licence, be sure to mention this to the optometrist so that the appropriate tests can be carried out.

If you have only a mild eyesight problem and can pass the legal standards without glasses, your optometrist may still suggest wearing glasses at night time anyway, for additional safety.

What can I do if I don’t meet the standard?

Often a pair of driving glasses, or a change in the strength of an existing pair, is all that’s needed to have you driving legally. If well-developed cataracts are limiting your vision, they can usually be removed surgically – in this case your optometrist will refer you to an eye surgeon.

If a temporary problem is affecting your vision, it may simply be a matter of not driving until the condition has resolved.

In other situations, a restricted licence may be a possibility. For example, your optometrist may recommend a licence restricted to daylight driving only, or within a certain radius of home.

Remember that if your vision does not meet a safe legal standard, by driving you are putting the lives of others at risk, and that your insurance may be void in the event of an accident.

Sunglasses and Driving Generally the best sunglasses are those that wrap around and protect the eyes from the side as well as the front. A neutral grey tint is best, as it doesn’t alter the colour of traffic signals. Polarising sunglasses are great for fishing and other water sports, but in a car they sometimes create distracting spotted patterns in laminated windscreens. Never wear any type of sunglasses or tinted lenses for driving at night – while they may seem to reduce glare from headlights, they also make everything else darker too. At night your eyes need more light, not less.

Other Hints

• Make sure your windscreen is clean and scratch-free, both inside and out, at all times.
• Ask your mechanic to check that your headlights are correctly aligned to provide good road illumination while not causing glare for other road users.
• Look slightly to the left of oncoming traffic at night to avoid suffering from glare which can take some time to recover from.
• If you need to wear glasses for driving, a spare pair is a good idea in case you lose or break your main pair.
• Any scratches or smudges on your driving glasses (or sunglasses) will increase glare – keep them clean!
• Remember to have regular eye examinations – every two years, or as advised by your optometrist.
  

This article was authored by Mr. Dom Willson B.Optom. Dom is an Optometrist in private practice in Newcastle, NSW.

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