The effects of impaired vision on simulated driving performance

Abstract

Introduction: Impaired vision can seriously compromise driving safety. The impact of eye diseases on driving ability can be various, including but not limited to blurred vision, reduced field of view, poor contrast, blind spots, or tunnel vision. Given this, it is understandable that various aspects of driving can be impaired. Visual acuity and field of view are commonly screened during driving exams. It can be questioned however if conducting these brief assessments is sufficient to identify all drivers who are impaired due to eye diseases. This notion is supported by driving simulator studies showing an increased number of accidents among patients with glaucoma [1], despite having a normal visual acuity (>0.5). Aim of the study: The purpose of this study was to assess driving performance in healthy volunteers wearing goggles that simulate various eye diseases. Methods: N= 49 healthy volunteers (N = 25 men, N= 24 women) with normal visual acuity (≥0.5) participated in this study. Participants were relative young (average age of 22.9 years old) with at least 3 years of driving experience (on average >5000 km per year). A driving simulator test was performed under normal vision conditions, and while wearing goggles that simulate glaucoma and homonymous hemianopia (group I, N= 24), or goggles that simulate cataract and diabetic retinopathy (group II, N= 25). The driving test scenario (Intersections, Vienna Test System Traffic, Schuhfried) comprised a drive through a small city, which included eight intersections. Outcome measures of the driving simulator test were investigator-rated number of (near) crashes, excursions out of lane, accurate behavior at crossings, gap acceptance. After the test, a visual analog scale was completed assessing subjective driving quality. Before the driving test, visual acuity was assessed using the Snellen test, and contrast sensitivity using the Hamilton-Veale Contrast sensitivity test. Driving test performance after simulated eye diseases were compared with those under normal vision conditions. Results: Visual acuity was significantly reduced in the cataract, diabetic retinopathy, and glaucoma condition (p <0.05), but not in the homonymous hemianopia condition. In the simulated glaucoma condition, participants produced significantly more excursions out of lane, had significantly more collisions and near collisions, and showed significantly reduced accuracy at crossings (p<0.05). In the homonymous hemianopia condition these effects did not reach significance. Both simulated cataract and diabetic retinopathy resulted in significantly more near crashes (p <0.05). In all four conditions, participants reported significantly reduced driving quality (p<0.05) when compared to the normal vision condition. Conclusions: Glaucoma, cataract, and diabetic retinopathy significantly impaired simulated driving performance. In the homonymous hemianopia condition, participants reported reduced driving quality, but this was not reflected in significant objective impairment on the driving simulator test. The data suggest it is important to screen drivers for eye diseases. As these eye diseases may develop long after obtaining a driver's license, additional driving tests may be useful when eye diseases are diagnosed.