The effects of age and glare on driving

This study aimed to characterise the visual experience and visual competence of commercial drivers. The effects of age and glare on contrast sensitivity, useful field of view and driving performance were evaluated.;In Experiment I, a cross-sectional study was carried out in Hong Kong for collecting the visual experience and studying the visual competence of current commercial drivers by conducting a personal interview and a vision assessment. In Experiments II to IV, three different groups of subjects were recruited and were divided equally into two age groups, the younger group (20-29 years) and the older group (50-59 years). In Experiments II and III, they were investigated for the effect of glare eccentricities on contrast sensitivity and useful field of view, respectively. In Experiment IV, the driving performance of the subjects in the presence of glare was studied using a self-built driving simulator. The effects of age and its interaction with glare were also investigated.;In Experiment I, the awareness of regular eye checks among the drivers was low. Tiredness, dry eye, glare intolerance, inadequate road lighting and crowded road signage were the most commonly encountered visual symptoms / difficulties at work. In Experiment II, peripheral contrast sensitivity deteriorated in the presence of glare but the age was a factor only for central contrast sensitivity, with the older group showing worse contrast sensitivity. In Experiment III, ageing did not affect the central processing speed in the useful field of view test. Both groups had reduced ability in the divided attention subtest. There was also a selective deterioration of performance when the glare was closer to the peripheral task. In the selective attention subtest, the younger subjects demonstrated an improved useful field of view in the presence of glare at different eccentricities, but this effect was not apparent in the older subjects except the glare at 2.5°. Younger subjects had better performance than older subjects in both the divided attention and selective attention subtests. In Experiment IV, different strategies (e.g. lower mean speed, lower mean speed before the road sign, decrease variation of lateral offset and longer completion time) in driving for compensating the glare were found in both groups. Moreover, glare had significant influence on the reaction time of them.;Glare is a visual disturbance in driving causing a deterioration of contrast sensitivity and useful field of view, especially in middle-aged / elderly drivers. Compensatory strategies in driving are adopted by drivers to cope with this adverse condition while the critical effect of glare cannot be omitted from those younger drivers.