Vision and driving

GPs must deal appropriately with patients' visual requirements for driving.

The Snellen chart is the usual method for testing vision (photograph: spl)
The Snellen chart is the usual method for testing vision (photograph: spl)

Driving is a complex skill and the law sets out the national medical guidelines of fitness to drive, which include the necessary visual standards.

The Driver and Vehicle Licensing Agency (DVLA) is responsible through its medical advisers to ensure that all licence holders are fit to drive.

Patients are often unaware of the visual requirements for driving. It is important that GPs can advise appropriately if visual problems occur that may make it unsafe for them to drive.

The visual requirements to drive a group 1 vehicle (car or motorbike) are simple. Visual acuity using both eyes together must be good enough to read a number plate at 20m in good light, using glasses or contact lenses if needed, and the visual field needs to be at least 120 degs on the horizontal plane, with no central binocular field defect.

The visual requirements for driving larger vehicles and public service vehicles are much more stringent and can be found on the DVLA website.

Identifying patients below the standard
Vision is measured with a Snellen chart and the driving standard is thought to lie approximately between 6/9 and 6/12.

Patients with binocular vision worse than 6/9 should be advised to check their vision using a number plate as described. If they are unable to read this they should inform the DVLA.

Patients with any visual field defect affecting both eyes should be advised to inform the DVLA.

This will include patients with glaucoma, hemianopia or quadrantanopia, and patients who have had laser treatment for diabetic retinopathy.

Many patients who are considered blind in one eye will still at least be able to detect light in that eye, but if a patient has no perception of light in one eye, they need to inform the DVLA.

Patients with vision in only one eye can continue to drive once they have adapted to this, assuming the visual acuity and visual field is adequate in the remaining eye. If the vision is lost in one eye, it is believed to take one month for adaptation to be sufficient to restart driving.

Patients who have an episode of transient complete loss of vision in one eye (amaurosis fugax) are in the same category as those suffering a TIA. They should be advised not to drive for one month, but do not need to inform the DVLA.

Diplopia and colour blindness
Patients with double vision should be advised not to drive and to inform the DVLA. If they are able to control their diplopia with prisms or occlude one eye and fulfil the guidance as described, they may be permitted to resume driving after discussion with the DVLA.

Patients who are colour blind are permitted to hold a driving licence and do not need to inform the DVLA.

Responsibility to inform the DVLA
If a patient has a medical condition that may prevent them from meeting the visual standards for driving, they must be informed of this. The patient needs to understand what the visual requirements are, and know that it is their responsibility to notify the DVLA.

If the visual acuity of a patient is in question, it is their responsibility to ensure they can read a number plate at 20m. If they are unable to do this, it is illegal for them to drive and their insurance is likely to be invalid. It is important to explain this.

If a patient does not notify the DVLA and continues to drive despite your advice, time should be taken to persuade the patient to do this. It may be helpful to talk with relatives, provided the patient gives consent.

If a patient still refuses to notify the DVLA or to stop driving, then the GP should contact the DVLA medical adviser and pass on this information in confidence. Before taking this step, the GP should advise the patient that the information is going to be disclosed.

Following disclosure, the patient should be informed in writing, and a copy kept in the record. If there are concerns about this procedure, the doctor may discuss it with their medico-legal defence organisation.

Where can I get further information?
The DVLA website provides useful information in the At a Glance Guide to the Current Medical Standards of Fitness to Drive, www.dft.gov.uk/dvla.

  • Mr Jackson is an ST4 in ophthalmology in the West Midlands.

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