Driver route-following and safety errors in early Alzheimer disease

Impaired visual search in drivers with Parkinson's disease

OBJECTIVE

To assess the ability for visual search and recognition of roadside targets and safety errors during a landmark and traffic sign identification task in drivers with Parkinson's disease (PD).

METHODS

Seventy-nine drivers with PD and 151 neurologically normal older adults underwent a battery of visual, cognitive, and motor tests. The drivers were asked to report sightings of specific landmarks and traffic signs along a four-lane commercial strip during an experimental drive in an instrumented vehicle.

RESULTS

The drivers with PD identified significantly fewer landmarks and traffic signs, and they committed more at-fault safety errors during the task than control subjects, even after adjusting for baseline errors. Within the PD group, the most important predictors of landmark and traffic sign identification rate were performances on Useful Field of View (visual speed of processing and attention) and Complex Figure Test-Copy (visuospatial abilities). Trail Making Test (B-A), a measure of cognitive flexibility independent of motor function, was the only independent predictor of at-fault safety errors in drivers with PD.

INTERPRETATION

The cognitive and visual deficits associated with PD resulted in impaired visual search while driving, and the increased cognitive load during this task worsened their driving safety.

Dementia and driving: autonomy versus safety

PURPOSE

This article reviews the effects of various types of dementia on driving skills, the available assessment measures, legal considerations, and the important role played by the nurse practitioner (NP) in the process of recommending driving cessation. It provides strategies and resources that may offer guidance to NPs who are attempting to balance the continued independence of patients with dementia, as represented by driving, with the safety not only of such patients but also of the public at large.

DATA SOURCES

A review of the biomedical literature, resources available on the World Wide Web, and illustrative case studies were used.

CONCLUSIONS

The diagnosis of dementia alone is often insufficient to determine driver competence because the topographic losses of dementia are complex. Recognizing when cessation should occur is made more difficult because objective assessment tools do not exist to predict impaired driving skills. Recommending driving cessation at the appropriate time can be a challenge for NPs, who must balance such a significant impact on the driver's autonomy with concerns about public safety if the patient continues to drive despite progressive impairment.

IMPLICATIONS FOR PRACTICE

The progressive loss of cognitive abilities in dementia presents a series of ongoing challenges for the patient throughout the disease continuum. Unfortunately, the recommendation to stop driving can present one of the more immediate issues confronting the patient, the family, and the healthcare provider. Failure to assess diminished driving skill can lead either to premature or to delayed driving cessation. Either outcome can have adverse effects on the patient, the patient's family, and public safety.

On-road driving with moderate visual field loss

PURPOSE

We examined the relationship between visual field extent and driving performance in an open, on-road environment using a detailed scoring method that assessed the quality of specific skills for a range of maneuvers. The purpose was to determine which maneuvers and skills should be included in future, larger scale investigations of the effect of peripheral field loss on driving performance.

METHODS

Twenty-eight current drivers (67 +/- 14 years) with restricted peripheral visual fields participated. Binocular visual field extent was quantified using Goldmann perimetry (V4e target). The useful field of view (UFOV) and Pelli-Robson letter contrast sensitivity tests were administered. Driving performance was assessed along a 14-mile route on roads in the city of Birmingham, Alabama. The course included a representative variety of general driving maneuvers, as well as maneuvers expected to be difficult for people with restricted fields.

RESULTS

Drivers with more restricted horizontal and vertical binocular field extents showed significantly (p < or = 0.05) poorer skills in speed matching when changing lanes, in maintaining lane position and keeping to the path of the curve when driving around curves, and received significantly (p < or = 0.05) poorer ratings for anticipatory skills. Deficits in UFOV performance and poorer contrast sensitivity scores were significantly (p < or = 0.05) correlated with overall driving performance as well as specific maneuver/skill combinations.

CONCLUSIONS

In a small sample of drivers, mild to moderate peripheral visual field restrictions were adversely associated with specific driving skills involved in maneuvers for which a wide field of vision is likely to be important (however most were regarded as safe drivers). Further studies using similar assessment methods with drivers with more restricted fields are necessary to determine the minimum field extent for safe driving.