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Binocular field loss from glaucoma may not affect driving
A “considerable subgroup” of patients with glaucoma who had binocular visual field loss passed a simulated driving test, compensating with an increased number of head and gaze movements, according to researchers in a study recently published in Optometry and Vision Science.
Thomas C. Kubler, MSc, and colleagues compared driving performance and visual search behavior among six patients with glaucoma and eight healthy age- and sex-matched controls in an advanced driving simulator, according to the study. During the 40-minute test, subjects experienced nine hazardous situations on a variety of roads. They were evaluated for lane position, time to line crossing and speed, as well as head and eye movements.
Kubler and colleagues reported: “Three out of six glaucoma patients passed the driving test, and their driving performance was indistinguishable from that of the control group.”
Those who passed showed an “increased visual exploration in comparison to patients who failed,” they continued. “That is, they showed increased number of head and gaze movements toward eccentric regions. Patients who failed the test showed a rightward bias in average lane position, probably in an attempt to maximize the safety margin to oncoming traffic.”
The researchers noted that they included in the study only subjects with binocular glaucomatous visual field loss, which would prevent them from obtaining a driver’s license in many areas.
“Therefore, our inclusion criteria might be less favorable than in other studies, and our sample is not representative of the general glaucoma population,” they said.
Kubler and colleagues noted that the type of visual compensation the patients in this study exhibited “improves traffic safety and may have practical implications in planning individualized driving fitness tests and driver rehabilitation programs.” – by Nancy Hemphill, ELS, FAAO
Disclosures: The authors report that Pfizer and MSD Sharp & Dohme GmbH supported this study. Daimler AG provided the moving-base driving simulator. Enkelejda Kasneci, PhD, acknowledged financial support from the Margarete-von-Wrangell program of the MWK Baden-Württemberg.
Perspective
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Assessing driving ability in glaucoma patients can be a complicated but necessary undertaking.
Glaucoma management should include an extensive discussion with our patients about their activities of daily living (including driving), especially in those with advanced visual field loss. If the patient is a driver, we should provide counsel about where they stand legally and, in some cases, notify the bureau of motor vehicles when a patient knowingly drives despite not meeting legal visual requirements.
This study highlights the compensatory eye movements used by drivers with visual field defects and may explain why some glaucoma patients report no difficulty driving despite not meeting legal requirements.