Visual and cognitive predictors of driving safety in Parkinson's disease patients

Abstract

This study assessed the clinical utility of contrast sensitivity (CS) relative to attention, executive function, and visuospatial abilities for predicting driving safety in participants with Parkinson's disease (PD). Twenty-five, non-demented PD patients completed measures of contrast sensitivity, visuospatial skills, executive functions, and attention. All PD participants also underwent a formal on-road driving evaluation. Of the 25 participants, 11 received a marginal or unsafe rating on the road test. Poorer driving performance was associated with worse performance on measures of CS, visuospatial constructions, set shifting, and attention. While impaired driving was associated with a range of cognitive and visual abilities, only a composite measure of executive functioning and visuospatial abilities, and not CS or attentional skills, predicted driving performance. These findings suggest that neuropsychological tests, which are multifactorial in nature and require visual perception and visual spatial judgments are the most useful screening measures for hazardous driving in PD patients.

Fig. 1

This is a schematic of the masking task. For each trial participants are shown a target letter (row one, column one), followed by a brief inter-stimulus-interval (row one, column two), followed by the mask (row one, column three). Participants then verbally indicate which of four letter options was just presented (row 1, column 4). If the participant is correct (as in trial 1) at the next trial the contrast of the target is reduced (row 2, column 1). This procedure continues until the participant commits and error (as in row 3, column 4) and then the contrast of the target letter is increased (row 4, column 1). This procedure continues until the accuracy criterion is reached.

Fig. 2

CS curves for safe and marginal drivers. The y-axis represents mean log CS values. The x-axis represents CPD. CS = contrast sensitivity, which is defined as the minimum difference between light and dark required to differentiate a figure from background. CPD = cycles per degree, which measures the frequency of spatial information contained in a visual scene.