The authors report on recent research into determining the level at whichbinocular visual field loss in the presence of good visual activity begins to impact on driving safely, once binocular scotomata in certain locations within the visual field reach a critical size. The project set out to study the implications for driving safety of paracentral scotomata; to examine the usefulness and limitations of currently available field tests and the proxy measures of driving safety; to quantify the reduction in visual performance resulting from impairment of other aspects of visual function within the central ± 20º; to examine the relationship, if any, between measures of visual performance and the proxy measures of driving safety. Literature reviews and experimental studies (acknowledging the constraints offinding legally licensed yet representative volunteers) were undertaken. The results indicate interpretation of visual field plots alone is an inadequate method of assessing drivers' vision, and in future a more complete visual assessment should be used in borderline cases. A new composite testcould be developed and would have to be seen by patients as clearly related to the driving task. Studying patients from early onset of visual field defect is recommended in order to learn more about compensation strategies developed by patients. (Author/publisher)
Abstract