Abstract
Abstract: :
Purpose: Although there is evidence that severe binocular peripheral visual field loss affects driving performance and elevates crash risk, little is known about the impact of more moderate field loss on real world driving performance. We conducted an on–road study to examine the relationship between visual field extent and driving performance in subjects with mild to moderate peripheral field loss. Methods: Twenty–eight current drivers (67 ± 14years) with restricted peripheral visual fields (mostly due to glaucoma) participated. Visual field extent was quantified using Goldmann perimetry (V4e target). Response speed under divided attention conditions was measured with the useful field of view (UFOV®) test. Driving performance was assessed along a 14–mile on–road course (Birmingham, Alabama). The course comprised a variety of normal driving maneuvers, including maneuvers that a priori would be expected to be difficult for people with restricted fields. Specific driving skills for each maneuver were rated on a 5–point scale. Results: More restricted horizontal binocular field extents were significantly (p < 0.05) correlated with poorer skills in gap judgment and speed matching when merging and changing lanes, and with poorer overall ratings for anticipatory skills, reaction to the unexpected in the roadway and overall driving performance. A restricted vertical field was significantly (p < 0.05) correlated with poorer performance in maintaining lane position and keeping to the path of the curve when driving around curves. Slower visual processing speeds on the UFOV tests were significantly (p < 0.05) correlated with poorer driving performance in skills or maneuvers involving anticipation, lane positioning before and after a maneuver, and curve taking. Conclusions: In a small sample of drivers, mild to moderate peripheral visual field restrictions were adversely associated with specific driving skills in maneuvers for which a wide field of vision is likely to be important. Further studies with drivers with more severely restricted fields are necessary to determine the minimum field extent for safe driving.
Keywords: low vision • visual fields