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Garrett Swan, Maha Shahin, Jacqueline Albert, Joseph Herrmann, Alex Bowers; The effects of simulated acuity and contrast sensitivity impairments on detection of pedestrian hazards. Journal of Vision 2018;18(10):1043. doi: https://doi.org/10.1167/18.10.1043.
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Driving is a highly visual task, yet the vision requirements for driving licensure vary widely. All states have a threshold for visual acuity (e.g. most use 20/40 for an unrestricted license, but visual acuity can be as low as 20/200 for a license that restricts driving to daytime or the local area only). Surprisingly, however, contrast sensitivity is rarely considered, despite evidence that it may be a better predictor of crash risk than visual acuity. In two experiments (n = 30), we investigated how simulated reductions in visual acuity and contrast sensitivity selectively affect the detection of pedestrians in a driving simulator. Young normally-sighted participants (20 – 40 years) wore goggles simulating different levels of visual acuity and contrast sensitivity loss (within a range that would meet licensing criteria) and detected pedestrians in a highway setting by pressing the horn as soon as they saw a pedestrian. The proportion of pedestrians detected was not different between the conditions. Reducing contrast sensitivity significantly increased reaction times (p < 0.005), while visual acuity only marginally increased reaction time (p < 0.1). When calculating the safety of the detection, which takes into account the speed of the car and pedestrian at the time of the horn press, only the combined reductions in visual acuity and contrast sensitivity significantly affected safety (p < 0.005). These results suggest that an individual's contrast sensitivity should be considered when determining visual fitness to drive, especially in the early stages of ocular disease, such as cataract, where contrast sensitivity may be impaired while high contrast acuity is still relatively normal. Contrast sensitivity may be the more relevant measure of visual function because distinguishing the hazard from the background is more important than determining what that hazard is.
Meeting abstract presented at VSS 2018
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