A descriptive and analytical study of visual functions in Danish drivers involved in automobile accidents has been performed. A total of 562 active (i.e. not passengers) road users, aged > years 10 involved in 359 car accidents resulting in human injury in the police district of Aarhus county (284,000 inhabitants) was registered: 405 car drivers (156 aged > 50 years) and 157 unprotected road users were included. The participation rate was 76%. The non-responders' vision was evaluated through contact to ophthalmologists or general practitioners. In this way vision data was obtained in 93% of the study group. A control group of 138 randomly selected active car drivers, aged > 50 years, were correspondingly examined with a participation rate of 83%. If available, police reports were studied in all relevant accidents. A case/control study was performed in 204 drivers (91 cases and 113 controls), aged > 50 years. Eighty-two vision/accident relevant case reports and 24 accident reports on medical conditions are published separately, 43 illustrated. Among the investigated car drivers involved in accidents, 1.6% aged < 50 years had a corrected visual acuity below the legal level at the time of the accidents. Correspondingly, the proportions were 8% in 50-69-year-old persons and 25% in drivers aged > 70 years. No significant differences could be demonstrated on visual parameters between males and females, although a longer period since last visual test was found in males (p< 0.01). In twelve out of 14 drivers (86%) with unilateral reduction of visual acuity, being involved in intersection accidents, the collision happened from the side with impaired vision (p< 0.02). Eleven of such bumpings (79%) took place from the left side (p< 0.06). A renewal of optical correction was sufficient to legalise the driver's vision in 15 of 17 accident drivers with visual acuity at (2) or below (15) the legal limit (88%, 95% confidence interval (CI):[64%-99%]. Tested binocularly, correspondingly 9 out of 10 drivers (90%) with visual acuity below 0.5 achieved legal vision after today=s standard by new glasses. In 16 % [CI: 10-23%] of the accident involved drivers aged > 50 years, an acute or chronic medical condition, including significant visual problems, was estimated to be of contributory importance for the accidents. Multiple logistic regression analyses with vision/accident risk estimates were carried out on 204 drivers aged > 50 years (the case/control study) with correction for age, sex, annual driving, daily alcohol consumption, percentage of urban and professional driving, and visual reaction time. Traffic accident risk was found to be significantly associated with quality of vision. Illustratively each accident is further individually evaluated for such an association. Contrast sensitivity (odds ratio (OR) = 1.99, [CI: 1.3-3.1], p= 0.003), and to a less degree unilaterally reduced visual acuity (OR=5.21,[CI: 1.3-20.6], p= 0.02), and binocular visual acuity (OR= 4.35, [CI: 1.1-17.5], p= 0.03) seemed to be important test variables. Binocular visual acuity was identified as a stronger risk indicator than monocularly tested visual acuity (OR= 3.65, [CI: 0.9-15.6], p= 0.08). It can not be ruled out that stereopsis (OR= 2.15, [CI: 1.0-4.7], p= 0.05) and the time interval since last visual test (OR= 1.55, [CI: 0.97-2.5], p= 0.07) are critical factors. No association was found with central or paracentral visual field defects, visual field defects tested a.m. Donders, colour vision defects or refraction. Several visual variables tested were found mutually associated. The health consequences of accidents with driver's visual acuity at or below the lawful limit did not differ from the main group of accidents. A vision/accident association is cautiously estimated as probable in 430 [216-761] traffic accidents with human injury in Denmark per year, or one per day. Elderly drivers' compensation for their increasing visual problems in the form of a change in driving behaviour is not fully adequate. One way to reduce the problem may be to perform more efficient and consistent re-testing of drivers' vision at appropriate intervals and with adequate procedures. Due to the fast growing population of elderly drivers world-wide, this seems increasingly relevant. Furthermore, when applied to relevant age groups, a screening program may to some extent function as a valuable health prophylaxis, including prevention of diseases and blindness. The implementation of such steps in individual countries, however, is a question of health politics. For selected group of drivers at doubt, modern visual attenuation test methods such as useful field of view and/or interactive driving simulators might be useful in the future. (Author/publisher)
Abstract