Peripheral visual processing and driving safety in later life : development of a screening test and congnitive intervention for older drivers

Abstract

One of many challenges presented by an ageing population is to ensure safe automotive mobility for an increasing number of older drivers. Self-monitoring of abilities, compensatory behavioural strategies and modem technologies can help older drivers to maintain their safety on the road. However, age-related changes in basic cognitive, physical and sensory abilities inevitably affect our ability to safely control a car. A holistic approach to this issue requires effective screening of older drivers to identify potential problems, and the development and implementation of interventions that have the potential to address such problems as or before they arise. This thesis reports on a program of three studies addressing both of these issues. Study 1 comprised three experiments aimed at developing a new screening paradigm (called the Test of Peripheral Vision; TOPS) to assess the efficiency with which the visual system can process information in the periphery. Results from a community sample of 281 older drivers revealed that visual processing performance declines into the periphery, but with a slower rate of decline on the horizontal visual axis than elsewhere. A novel algorithm was developed to fit visual performance fields to the data, and results showed that visual processing abilities can be better characterised in shape by an ellipse than by a circle. Both of these findings are discussed in terms of previous results from the field of vision science, and their theoretical support for a widely used older driver screening instrument called the Useful Field of View (UFOV{u00AE}). Study 1 also examined the relationship between age, visual processing abilities as assessed by the TOPS paradigm, and a range of cognitive and visual measures. Results showed that performance on the TOPS measure was only weakly associated with age, and that this relationship was completely mediated by a set of basic cognitive and sensory variables, whereas the UFOV{u00AE} demonstrated a stronger initial association and significant residual variance. Study 2 was designed to validate the TOPS instrument using an on-road assessment. A sample of 52 older drivers completed a battery of cognitive and visual tests as well as a comprehensive driving test. A set of weightings derived from logistic regression analysis revealed that the TOPS test was able to classify safe and unsafe drivers with 61.5% sensitivity and 79.5% specificity, while a set of cut-points derived from a receiver operating characteristics (ROC) analysis achieved 92.3% sensitivity and 41% specificity.The predictive validity of the measure was much better than for the UFOV{u00AE}, a finding that may be explained by the high-functioning study sample. Finally, Study 3 piloted a brief, dynamic cognitive training procedure that focused on improving information processing efficiency in the visual periphery. 21 older volunteers each completed nine sessions of a randomised crossover trial (RXT) that found significant improvements on the abilities being trained, but limited transfer to other domains of processing. Theoretical and practical implications of all three studies are discussed with reference to additional research that is still required to achieve concrete improvements in road safety for older drivers. Show more