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Visual driving standards

Discussion

The Department of Environment and Local Government’s Green Book (1999) gave guidelines on the medical requirements for driver licensing. The eyesight requirements were 0.5 (6/12) both eyes open and a binocular horizontal field of 150 degrees. For a one-eyed person, the vision requirements were >0.6 (6/9.5). For Class II, the acuity standards were slightly higher.

Following a lengthy consultative period with many medical and safety bodies, the Road Safety Authority (RSA) subsequently issued new guidelines, Sláinte agus Tiomáint – Medical Fitness to Drive Guidelines in 2013. The guidelines were developed by the National Programme Office for Traffic Medicine, which was established in 2011 as a joint initiative between the RSA and the Royal College of Physicians of Ireland.

The guidelines are intended for use by any health professional who is involved in assessing a person’s fitness to drive. The most recent edition (Group 1 and Group 2 Drivers, 4th edition) was published in March 2015 and was only made available electronically on www.rsa.ie and www.ndls.ie. Health professionals are advised to review these websites for updates and changes.

Responsibilities

Health professionals now have a responsibility to report to the National Driver Licence Service (NDLS) where there is a risk to the public if the driver cannot or will not cease driving.

This new duty has the potential to bring health professionals into conflict with patients, which the RSA acknowledges and advises on. The Authority states that breaches of medical confidentiality are acceptable to the Medical Council on grounds of public safety, ie, the document states: “… there are, on rare occasions, ethically and/or legally justifiable reasons for breaching confidentiality…. The Irish Medical Council Guidelines provide for breach of confidentiality if the driver represents a risk to the safety of others, refuses or cannot inform the NDLS, fails to stop or adapt driving appropriately, and is not amenable to appropriate persuasion and discussion.” We would, however, advise also checking with the Medical Council first.

Visual requirements

The medical fitness to drive guidelines provide detailed information on the examination of visual acuity and visual fields and outline the new vision requirements. These are: visual acuity 0.5 (6/12), a visual field of 120 degrees horizontally and 40 degrees vertically (20 degrees up and down). No defect can be present within the central 20 degrees.

Vision is a vital contributor to driving safety. A total of 85 per cent of sensory input for successful and safe driving derives from the visual system. Visual attributes involved with driving safely and effectively go well beyond high contrast static visual acuity (HCVA), embracing complex integrative processes such as colour perception, contrast sensitivity, stereopsis and depth perception, ocular motility and tracking, dynamic visual acuity, visual perception, motion detection and night-time visual performance, as well as the closely-integrated cognitive neuromuscular, vestibular and other neurological inputs.

Visual acuity is our ability to see a target; it is one thing to recognise that something is there but entirely a different matter to resolve enough of its detail to identify what it is, where it is going and how to initiate a response to it. HCVA, as tested on Snellen or logMAR charts, while a gross indicator of visual function in ideal conditions, does not always correlate how we will see under reduced lighting or degraded visual environments. We generally do not check low-contrast visual acuity, contrast sensitivity or dynamic visual acuity.

Using the included case reports in this article, we would like to draw attention to the need for more detailed examination rather than just a cursory check of visual acuity and visual field assessment by confrontation. All of these cases were approved to drive by health professionals, though all were unfit to do so. What happens if someone who is approved to drive is involved in an accident? Is the health professional liable if it can be shown that the driver should not have been approved in the first place? In this litigious era, can a claim be made against the health professional? Are drivers who have been incorrectly approved insured or could you be carrying a liability?

Cases discussion

All of the case report subjects in this article were holders of a driver’s licence and had been approved as meeting the required visual standards.

All passed the visual acuity component of the guidelines but not the visual fields assessment. Anecdotally, most people feel that if they can see straight ahead and pass the vision test (6/12), they are fit to drive. However, these cases show they do not fulfil the driving licence standards.

Most visual field defects are negative scotoma; they will not be perceived as darker areas. Through some psycho-perceptual mechanisms, the brain fills in the defective area, leading to a false picture covering up the visual field defect. The patient then believes that their visual field is normal.

We would thus caution any health professional (medical or optometric practitioner) before approving an applicant as being fit to drive to ensure that as well as meeting visual acuity standards, that they also meet the visual field requirements.

As the RSA guidelines state, health professionals should keep informed of any changes in healthcare and health technology that may affect their assessment of drivers. They should also maintain an awareness of any changes in the law that may affect their legal responsibilities.

Specifically, the RSA guidelines state it is the medical professional’s responsibility to:

  • Assess the person’s medical fitness to drive based on the current Sláinte agus Tiomáint medical standards.
  • Advise the person regarding the impact of their medical condition or disability on their ability to drive and recommend restrictions and ongoing monitoring, as required.
  • Advise the person of their responsibility to report their condition to the NDLS if their long-term or permanent injury or illness may affect their ability to drive.
  • Treat, monitor and manage the person’s condition with ongoing consideration of their fitness to drive.
  • Report to the NDLS regarding a person’s fitness to drive in the exceptional circumstances where there is a risk to the public and the driver cannot or will not cease driving. 

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Case 1: Binocular field

Case report 1

A 61-year-old female was admitted to hospital with a left cerebrovascular accident (CVA) and loss of right-sided vision. The patient held a current driving licence. On examination, visual acuity was 6/6 in the right eye and 6/9 in the left eye. Visual fields showed a right homonymous quadrantic field defect. The patient was advised by the ophthalmologist that she should not drive. On review of her visual fields three months later, she informed the eye clinic that she had made a good recovery from her stroke and had been advised by other medical practitioners that she could drive one month post-stroke. However, her visual field defect at the three-month review was still present and persisted one year after her CVA. She was advised not to drive but if she was unhappy she could seek a second opinion through the RSA, which might give her a waiver but that she would then have to declare this to her insurers.

Case report 2

A 71-year-old male presented with blurred vision and was found to have a right hemianopia. CT showed a left occipital infarct. He had a previous history of a left carotid disease and stenting. Visual acuity was 6/9 right and left, visual fields showed a right homonymous hemianopia. He wanted to drive as he lived in a remote rural area and he felt as he could walk and see well, he was fit to drive. He held a valid driving licence. However, he was advised not to drive and his visual fields have shown little improvement on two subsequent tests.

Case report 3

A 76-year-old male was admitted with left leg and arm numbness and tingling and a right CVA was diagnosed. Visual acuity was 6/12 in the right and left eye, 6/9 part binocularly. Visual field testing showed a left homonymous hemianopia and he was advised not to drive. Pressure was applied by other health professionals to allow this man to drive. A copy of the visual fields was supplied to his health professionals to demonstrate the visual field defects.

Case report 4

A 28-year-old male, the holder of a provisional driver’s licence, presented to the eye clinic. He had a history of premature birth, being a ‘clumsy’ child and had had squint surgery. On examination, visual acuity was 6/6 in the right and left eye, he had a right divergent squint and his visual fields were grossly abnormal. He was subsequently diagnosed as having an unusual neurodevelopmental disorder. He was advised not to drive, which he accepted.

Case report 5

A 25-year-old male, the holder of a valid driver’s licence, presented with visual acuity of 6/6, right and left, but visual fields revealed a right homonymous hemianopia. He had a history of a head injury with left occipital damage at the age of 10 years. On questioning, he admitted to multiple crashes on his right side. He was reluctant to accept the findings, as he “needed” to drive. His health professionals were informed and sent a copy of the visual field results.

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