Trent P. Carberry

Bilateral cataract surgery and driving performance

Background: Cataract surgery is one of the most common medical procedures undertaken worldwide. Aims: To investigate whether cataract surgery can improve driving performance and whether this can be predicted by changes in visual function. Methods: 29 older patients with bilateral cataracts and 18 controls with normal vision were tested. All were licensed drivers. Driving and vision performance were measured before cataract surgery and after second eye surgery for the patients with cataract and on two separate occasions for the controls. Driving performance was assessed on a closed-road circuit. Visual acuity, contrast sensitivity, glare sensitivity and kinetic visual fields were measured at each test session. Results: Patients with cataract had significantly poorer (p<0.05) driving performance at the first visit than the controls for a range of measures of driving performance, which significantly improved to the level of the controls after extraction of both cataracts. The change in contrast sensitivity after surgery was the best predictor of the improvements in driving performance in patients with cataract. Conclusions: Cataract surgery results in marked improvements in driving performance, which are related to concurrent improvements in contrast sensitivity.

Effects of age and auditory and visual dual tasks on closed-road driving performance

Purpose. This study investigated how driving performance of young and old participants is affected by visual and auditory secondary tasks on a closed driving course. Methods. Twenty-eight participants comprising two age groups (younger, mean age = 27.3 years; older, mean age = 69.2 years) drove around a 5.1-km closed-road circuit under both single and dual task conditions. Measures of driving performance included detection and identification of road signs, detection and avoidance of large low-contrast road hazards, gap judgment, lane keeping, and time to complete the course. The dual task required participants to verbally report the sums of pairs of single-digit numbers presented through either a computer speaker (auditorily) or a dashboard-mounted monitor (visually) while driving. Participants also completed a vision and cognitive screening battery, including LogMAR visual acuity, Pelli-Robson letter contrast sensitivity, the Trails test, and the Digit Symbol Substitution (DSS) test. Results. Drivers reported significantly fewer signs, hit more road hazards, misjudged more gaps, and increased their time to complete the course under the dual task (visual and auditory) conditions compared with the single task condition. The older participants also reported significantly fewer road signs and drove significantly more slowly than the younger participants, and this was exacerbated for the visual dual task condition. The results of the regression analysis revealed that cognitive aging (measured by the DSS and Trails test) rather than chronologic age was a better predictor of the declines seen in driving performance under dual task conditions. An overall z score was calculated, which took into account both driving and the secondary task (summing) performance under the two dual task conditions. Performance was significantly worse for the auditory dual task compared with the visual dual task, and the older participants performed significantly worse than the young subjects. Conclusions. These findings demonstrate that multitasking had a significant detrimental impact on driving performance and that cognitive aging was the best predictor of the declines seen in driving performance under dual task conditions. These results have implications for use of mobile phones or in-vehicle navigational devices while driving, especially for older adults.

Using reflective clothing to enhance the conspicuity of bicyclists at night

Bicycling at night is more dangerous than in the daytime and poor conspicuity is likely to be a contributing factor. The use of reflective markings on a pedestrians major joints to facilitate the perception of biological motion has been shown to greatly enhance pedestrian conspicuity at night, but few corresponding data exist for bicyclists. Twelve younger and twelve older participants drove around a closed-road circuit at night and indicated when they first recognized a bicyclist who wore black clothing either alone, or together with a reflective bicycling vest, or a vest plus ankle and knee reflectors. The bicyclist pedalled in place on a bicycle that had either a static or flashing light, or no light on the handlebars. Bicyclist clothing significantly affected conspicuity; drivers responded to bicyclists wearing the vest plus ankle and knee reflectors at significantly longer distances than when the bicyclist wore the vest alone or black clothing without a vest. Older drivers responded to bicyclists less often and at shorter distances than younger drivers. The presence of a bicycle light, whether static or flashing, did not enhance the conspicuity of the bicyclist; this may result in bicyclists who use a bicycle light being overconfident of their own conspicuity at night. The implications of our findings are that ankle and knee markings are a simple and very effective approach for enhancing bicyclist conspicuity at night.

OLDER DRIVERS AND CATARACTS: MEASURES OF DRIVING PERFORMANCE BEFORE AND AFTER CATARACT SURGERY

Cataracts are the main cause of reversible vision impairment in older adults. An investigation examined how cataracts and cataract surgery affected driving performance and determined whether any changes in driving performance could be predicted by self-reported perceptions of driving and vision. Twenty-eight older participants with bilateral cataracts and eighteen age-matched control participants with normal vision were tested. All were licensed drivers. Driving and vision performance were measured before cataract surgery, after first-eye surgery, and again after second-eye surgery for the cataract participants and on three separate occasions for the control group. Driving performance was assessed on a closed-road circuit. Visual acuity and contrast sensitivity were also measured at each test session. Self-perceptions of vision and driving were assessed with the Activities of Daily Vision Scale (ADVS). The participants with cataracts had significantly poorer (p <.05) driving performance at the first visit compared with the control participants for a range of measures of driving performance, which significantly improved to the level of the control participants following cataract extraction. Self-perceived changes in driving performance assessed with the ADVS were not strongly related to the actual changes in driving performance recorded. Together these findings indicate that participants with cataracts have poorer driving and vision performance than age-matched control participants and that cataract surgery can result in significant improvements in driving, which are not predicted by self-reported measures such as the ADVS.

Differential Effects of Refractive Blur on Day and Nighttime Driving Performance

PURPOSE To investigate the effect of different levels of refractive blur on real-world driving performance measured under day and nighttime conditions. METHODS Participants included 12 visually normal, young adults (mean age = 25.8 ± 5.2 years) who drove an instrumented research vehicle around a 4 km closed road circuit with three different levels of binocular spherical refractive blur (+0.50 diopter sphere [DS], +1.00 DS, +2.00 DS) compared with a baseline condition. The subjects wore optimal spherocylinder correction and the additional blur lenses were mounted in modified full-field goggles; the order of testing of the blur conditions was randomized. Driving performance was assessed in two different sessions under day and nighttime conditions and included measures of road signs recognized, hazard detection and avoidance, gap detection, lane-keeping, sign recognition distance, speed, and time to complete the course. RESULTS Refractive blur and time of day had significant effects on driving performance (P < 0.05), where increasing blur and nighttime driving reduced performance on all driving tasks except gap judgment and lane keeping. There was also a significant interaction between blur and time of day (P < 0.05), such that the effects of blur were exacerbated under nighttime driving conditions; performance differences were evident even for +0.50 DS blur relative to baseline for some measures. CONCLUSIONS The effects of blur were greatest under nighttime conditions, even for levels of binocular refractive blur as low as +0.50 DS. These results emphasize the importance of accurate and up-to-date refractive correction of even low levels of refractive error when driving at night.

Effects of Age and Auditory and Visual Dual-Tasks on Closed Road Driving Performance

The aim of this study was to understand how visual and auditory dual tasks impact upon the driving behavior of young and old participants. The effect of a secondary task on measures of driving performance including the recognition of road signs, detection and avoidance of large low contrast road hazards, judgment of cone gaps, and time to complete the course was assessed for young and older participants as they drove around a 5 km closed road driving course. The secondary task required participants to verbally report the sums of pairs of numbers presented either through a computer speaker (auditorially) or via a dashboard mounted monitor (visually) while driving. The results show that drivers reported fewer road signs, increased their time to complete the road course, and misjudged cone gaps more frequently under the dual-task (visual and auditory) conditions compared to the single task condition and these effects were greater for the older participants.

Effect of arrow shaft straightness on arrow grouping

Arrows are available in various straightness grades. Their grouping ability as the straightness varied was assessed using a compound bow and shooting machine. The research showed that archers would benefit from selecting arrows with the highest straightness grades (as might be expected). In addition, nock selection was determined to significantly impact group size. The fletches needed to be set at an angle to the longitudinal axis of the arrow shaft in order to have the arrows spin while in free flight, as that further reduced the group size.

On-road measures of the visibility of pedestrians at night

Most collisions between vehicles and pedestrians occur at night. This experiment quantified the ability of drivers to detect pedestrians at night. Ten younger (M=27.8 yrs) and ten older (M=67.9 yrs) participants drove an instrumented car ten laps around an unilluminated 1.1 mile test track. Drivers pressed a dash-mounted touchpad when they recognized the presence of a pedestrian. A computer-based system measured recognition distances by interpreting the parallax provided by two synchronized digital video cameras mounted on the cars roof. Two pedestrians walked in place at different positions on the far shoulder. One pedestrian was in darkness and one was positioned just beyond a stationary pair of headlights that was a source of glare for the approaching driver. Across laps, drivers used both low and high beams and pedestrians wore four different clothing configurations. The effects of age, glare, clothing, and beam all significantly influenced both pedestrian identification (all p < .01) and recognition distance (all p < .001). With and without glare, older drivers identified only 48% and 59% of the pedestrians, respectively. Younger drivers identified significantly more pedestrians (75% with glare, 94% without glare). Recognition was worst for pedestrians wearing black (34% identified). Only 5% of drivers identified the black-clad pedestrian when the driver used low beams and faced glare. Recognition was best (94% identified) for pedestrians wearing retroreflective markings configured to depict biological motion. Analysis of the recognition distances revealed that when identification occurs it is often at a distance insufficient to allow a successful avoidance maneuver. Taken together, these data confirm that even alerted drivers can have great difficulty recognizing the presence of pedestrians at night. The problem is greatest for older drivers, when drivers rely on low beams, when pedestrians wear low reflectance clothing, and when glare is present.