Visual Standards For Driving Licenses

Prior to visual requirements for driving license, certain factors, such as driver education should also be assessed and the street and vehicle lighting
should be improved.
The drivers' attitudes through education is the simplest way to reduce accidents. For example, the average driver's behaviour and road speed apparently change very little, regardless of the time of day and the level of visibility.
Although it will be expensive to provide education for drivers and improve road and vehicle lighting, the cost in human suffering and the estimated cost of road traffic accidents, must be taken into account.

Standards for private motorists

It is very necessary for drivers of private vehicles to satisfy a minimum visual standard.

Drivers with double vision are considered unfit to drive unless the diplopia can be overcome by a prismatic correction. Binocular field defects such as bitemporal hemianopia or homonymous hemianopia, if complete or substantial in the lower quadrants, are a bar to driving. A binocular visual field of less than 120 degrees is considered unsafe. A driver with one eye may drive provided the visual field is full. However, the recent loss of an eye may require a short adaptation period.

Drivers who suffer from insulin-dependent diabetes need to have their license renewed every 3 years, when medical evidence will be required to support its renewal.

Drivers are required to read a number plate in good daylight (with glasses or contact lenses if worn) containing letters and figures 79.4mm high at a distance of 20.5m. The number plate test is not considered to be a good test. One major point of criticism is that test conditions are poorly controlled, e.g. lighting, distance and type and cleanliness of number plate. 

The standard of visual acuity required to read the number plate is greater than the nominal Snellen equivalent of 6/15. On examination of those who failed the number plate test, it was found to be equivalent to a clinical Snellen value of about 6/9-2. The number plate test is often considered to be irrelevant to the driving situation, as it is a static test in goog daylight.

Other tests of visual competence should be checked, such as visual field, dynamic visual acuity and contrast sensitivity.

The test is carried out at the time of the driving examination and is not repeated until the age of 70 years. It has been suggested recently that drivers applying for provisional license should be tested and drivers over 50 years of age should be examined at regular intervals. At present the driving license is valid until the age of 70 years, with renewal every 3 years thereafter. Most people are not good at assessing whether their vision is up to standard, which was one reason why a number plate was used to enable self-checking. However, various studies show an alarmingly high percentage of drivers who are ignorant of the visual standard required.

Large goods and passenger-carrying vehicles license

Drivers still need to pass separate tests and meet higher medical standards before they can drive lorries and buses. The terms 'heavy goods vehicle' (HGV) and 'public service vehicle' (PSV) have been renamed 'Large Goods Vehicle' (LGV) and 'passenger Carrying Vehicle, (PCV), respectively. 

The eye sight standards require new drivers to have a visual acuity of not less than 6/9 in the better eye and not less than 6/12 in the other eye, with corrective lenses including contact lenses, if worn. They must also meet an uncorrected standard of not less than 3/60 in each eye. All drivers who have monocular vision, diplopia, defective binocular vision or visual field defects should be regarded as unfit to drive LCV or PCVs.

If drivers need to wear glasses or contact lenses they must have an uncorrected acuity in each eye of not less than 3/60. The uncorrected standard of vision (3/60) effectively precludes from driving those who have had a cataract removed from one or both eyes, unless an ultra-ocular lens has been inserted. The license is valid up to the age of 45, or for 5 years, whichever is longer. From the age of 45 renewals are required every 5 years and from the age of 65, annually.

The driver also has to pass a general medical examination before being declared fit to drive. Some of the conditions that make it unsafe to drive are: disorders of the heart, circulation, brain and nervous system; mental illness; and addiction to alcohol and drugs. A vactional license will not be granted to an applicant who has suffered from an epileptic attack after the age of five or to insulin-dependent diabetics.

Drivers are also required to inform their driving licensing body, if any illness or disability develops or worsens, unless (like a sprained ankle) it is likely to get better within 3 months.

Any medical practitioner who is in any doubt about the advice that should be given a patient about fitness to drive in any particular case, can discuss the matter with the Medical Adviser to the Department of Transport.

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