Vision and Driving

VISION AND DRIVING

When driving, the two most important things about your eyesight are how clearly you can see into the distance, or visual acuity, and how much you can see of what is going on around you, outside your line of direct vision. This is known as the visual field.

National uniform guidelines on fitness to drive of private vehicle drivers have been developed by the Austroads Council. These have been approved by all of Australia's driver licensing authorities since 1998 and replace all previous fitness to drive guidelines.

VISUAL ACUITY

When you apply to obtain or renew a license, your vision may be tested and measured by a scale which indicates the size of letters you can read, and at what distance. The minimum requirement for driving a private vehicle is a binocular visual acuity of at least 6/12. If corrective lenses are required to achieve this acuity, those lenses must be worn when driving.

This does not mean that each eye must see 6/12. One eye may be considerably worse than 6/12 provided the binocular vision meets thestandard.

The acuity of both eyes is assessed in considering light and heavy truck, and public transport, vehicle licenses.

VISUAL FIELD

A good visual field is important when driving, as you must be able to see vehicles and pedestrians outside your line of direct vision. Most people have a visual field of about 170 degrees - but for driving a car, a span of about 120 degrees is legally acceptable.

Again, the requirements may be higher for drivers of buses and other heavy vehicles.

Visual field width and height may be reduced below the legal limit for driving by CVAs (strokes) and some eye diseases e.g. glaucoma and retinitis pigmentosa. Quantification by an Ophthalmologist is required. Conditional licenses may be granted where an applicant's field fails to meet the standard.

SPECIFIC VISUAL FIELD DEFECTS

• Total hemianopia - should not drive Partial hemianopia - conditional license possible subject to eye specialist's report being accepted by the licensing authority. Quadrantanopia - conditional license possible subject to eye specialist's report being accepted by the licensing authority.

OTHER EYE DEFECTS WHICH COULD CAUSE PROBLEMS

Colour Vision Defects - Mild defects of colour vision do not usually cause problems, but it helps to be aware of any limitations you may have. In some States, drivers with defective colour vision may be excluded from driving certain kinds of vehicle, such as trucks or taxis.

Poor Night Vision - People with eye diseases such as a advanced cataract, or retinal disorders might have difficulty seeing at night. They should not drive until assessed for a conditional daylight license.

Double Vision - Double vision or "diplopia" may be sudden and short-term or chronic. All instances should be assessed for cause, potential for treatment and risk to safe driving. Driving should not be attempted until specifically advised that it is safe.

Loss of Vision in One Eye - You should not drive for three months after loss of binocular vision. Thereafter, the better eye must achieve 6/12 vision.

Conditions which reduce the visual acuity in one eye can significantly impair distance judgement and increase the risk of accident. Corneal ulcerations both infective and traumatic, eye patches, asymetrical macular degeneration, retinal detachments and retinal circulation problems can all suddenly change distance appreciation.

REMEMBER

You must be able to see properly to drive safely. If your eyesight is worrying you, tell your family doctor. If necessary, you will be referred to an Ophthalmologist who will examine your eyes thoroughly and will prescribe glasses or other forms of treatment to bring your vision up to a standard for driving.

Safe vision for driving goes beyond your eyes! Make sure your windscreen is clean and unscratched -scratches can cause glare. Adjust rear-view and side mirrors properly, and don't let passengers or luggage block your view through rear and side windows.

FURTHER INFORMATION

Assessing fitness to drive - Austroads guidelines for health professionals and their legal obligations. Austroads Publication No AP-56/98, Austroads Inc 1998