A Functional Evaluation of Driving Performance for Drivers with Cataracts: Licensing Implications

Abstract

In the design for this study we intended to use three groups of ten subjects: Younger Drivers; Older Drivers who were free of clinically significant cataracts; and drivers with advanced stage Cataracts. Data collection was completed for the first two groups and we collected data on six of the ten cataracts patients. During a greatly protracted delay due to simulator problems, Dr Melick completed her training and moved from Minnesota. We were unable to secure more cataract patients as subjects nor could we obtain the visual function data on the six cataracts patients we had tested in the simulator. This loss of subjects and data greatly reduced the intended scope of this study. This report will be written according to the changed circumstances for this project rather the original intent of the project. The results reported here are based on statistical analyses of the same three groups of subjects but with only six subjects in the Cataract group. The data are restricted to target detection data and driving performance data. Based on this limited analysis we found, as expected, that younger subjects exhibited greater sensitivity in their ability to detect targets than older subjects who in tum were more sensitive than subjects with cataracts. We also found, again as expected, that younger subjects had a greater bias toward stating that a target was present than older subjects who needed slightly less data to state that a target was present than cataract subjects. Our initial hypothesis was that older subjects would need more time to confirm that a target was present than older drivers and that this need for more time would be further extended for subjects with cataracts. This was confirmed. However, we further expected that the increased time needed for target detection by older subjects and by subjects with cataracts would result in less attention being paid to the driving task and therefore, a degradation of driving performance. This prediction was partially confirmed by the data for response time to the onset of simulated brake lights. Older subjects were significantly slower than younger subjects but while cataract subjects were slower than younger subjects, the difference was not significant. Older subjects had slower response times than Cataract subjects but again, this difference was not significant. For both the steering data (keeping the car centered in the lane) as well as for the speed maintenance data there were not significant differences among groups.