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Editors Selection IGR 11-1

Driving Performance

Comment by James Brandt on:

21724 Glaucoma and on-road driving performance, Haymes SA; Leblanc RP; Nicolela MT et al., Investigative Ophthalmology and Visual Science, 2008; 49: 3035-3041

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Ophthalmologists frequently encounter patients who continue to drive despite significant vision loss, potentially endangering themselves and their families along with others on the road. It is relatively easy to document and convince a patient and their family that grandmother should stop driving when her best corrected vision is 20/100 and the government requires 20/40 vision to drive. But what about the glaucoma patient with 20/20 central vision and severe visual field loss in both eyes? Such a patient will not be identified by the crude vision screening at the local Department of Motor Vehicles (DMV). Intuitively it makes sense that good peripheral vision is needed to drive safely, but the evidence that this is the case is remarkably limited. A review of 10,000 DMV records by Johnson and Keltner in the 1980s showed that individuals with bilateral visual field loss had accident and conviction rates twice that of individuals with normal visual fields. Subsequent studies using computer-based driving simulators have confirmed that drivers with significant visual field loss have trouble scanning their surrounding environment while driving and can't easily anticipate merging traffic, peripheral obstacles and potential collisions with cars and pedestrians. In most jurisdictions, all an ophthalmologist can do is refer patients with significant visual field loss to the DMV for a 'real life' driving test with a driving examiner, who ultimately will decide whether the patient is 'safe' to drive. Haymes et al. (924)

Although there is no difference between glaucoma patients and controls in their ability to complete required driving maneuvers, 60% of glaucoma patients had one or more interventions by the instructor/ tester compared to 20% among controls

from Dalhousie University in Halifax recently performed the first controlled studies of such 'real world' driving tests in twenty patients with known glaucomatous visual field loss and compared their on-road driving performance to twenty age-matched controls. Using a standard driving school automobile equipped with dual braking, participants drove a standardized 10 km course through residential and business districts in Halifax. Participants were scored both on whether they completed the required maneuvers correctly and safely, and also whether the instructor/tester (who was masked as to the subject's diagnosis) needed to intervene (i.e., applied the dual brake or took over steering to avoid a potential collision).

The investigators found no difference between glaucoma patients and controls in their ability to complete the required maneuvers. However, 60% of glaucoma patients had one or more interventions by the instructor/tester compared to 20% among controls. Most of these interventions were due to failure of the driver to see and yield to a pedestrian. As our population ages and more and more elderly patients continue to drive with significant eye disease, it is imperative that ophthalmologists ask about driving at every opportunity.

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