Vision and Driving after Stroke

Driving a car is often an essential part of maintaining mobility and quality of life, but after a stroke many are forced to cease driving. Homonymous visual field defects (HVFDs) and unilateral spatial neglect (USN) are common sequelae of stroke. For people with HVFDs a legal threshold for extent of field loss exists beyond which a person is not allowed to drive, and most people with clinically detectable USN are also censured from driving. However, some people with HVFDs have been deemed safe to drive, and some with USN have shown normal performance on other skilled visuo-motor tasks. It seems that there is great variation in abilities across individuals with HVFDs and USN, and driving performance cannot be predicted from simple measures such as extent of visual field loss. Several studies have suggested that compensatory eye-movement strategies (particularly saccades into the affected visual field) may be linked with functional improvements post-stroke.

This thesis investigates whether eye-movement behaviours are important for stroke patients performing skilled actions such as driving. To test this theory 18 people with HVFDs and/or USN following a stroke and 18 older adult controls were recruited. A series of behavioural measures were taken using a battery of tests: Cognitive and visuospatial measures from classic pen and paper tasks and visual field mapping, saccadic and smooth pursuit accuracy, visual search, simulated steering and simulated hazard perception measures. Across these measures there was a consistent theme that impairments to perception-action functions varied considerably across participants with stroke, but that some individuals were able to function remarkably well. Compensatory eye movement patterns were observed in many, and driving performance was predicted to some extent by saccadic accuracy and visual search performance. The implications are discussed with respect to using eye-movements as a potential target for rehabilitation treatment.