Abstract
Abstract: :
Purpose: To determine vision standards for uncorrected NYPD police officers under realistic conditions, as with use of a real gun, typical environments, and NYPD recommended scenarios. Prior studies of police tasks have been conducted using relatively abstract simulations where the fear or confusion which occurs under real conditions could not affect outcomes. Realism is important for determining visual standards for the unique tasks of large-city police officers. Methods: Critical Incidence vision tasks are where an officer loses their corrective lenses, usually violently, and must function with uncorrected vision.These were identified using ride-alongs, interviews, surveys, and meetings with NYPD officers and administrators. An initial survey was culled for visual tasks with high levels of importance. A list of 82 tasks was identified and presented to 242 NYPD officers. They rated tasks by frequency of occurrence and consequence of failed performance. They also identified the most typical viewing distances and lighting conditions. The consequence of failed performance was used as the key determinant of criticality for task scenario development. The inter-rater reliability for rating was 0.9645 indicating good agreement among officers, important as failure to perform the task with poor visual acuity from using uncorrected vision can lead to serious or fatal injury and/or significant property damage. Four simulations of critical tasks were then constructed, three related to visual acuity and one to visual field. Sample size determination for a one-factor repeated measures design dictated a sample size of at least four subjects for 0.80 statistical power. Results: To identify "gun-no gun' in daylight at 25 yards, 20/32 or better acuity was required. However, to identify "gun-no-gun' at night at 25 yards gave only 60% correct responses with 20/20 acuity. For nighttime distances of 15 yards, 7 yards, & 14 feet, at least 20/20, 20/63, and 20/100 or better acuity was required, respectively, to correctly identify the real weapon among other similar common objects. Restricted visual fields inhibited accurate vehicle search although head turning could partially ameliorate this deficit. Conclusions: The acuity experiments demonstrate that only with uncorrected acuity of 20/20 or better can individuals reliably detect a weapon under both daytime and nighttime conditions with highest accuracy. As nearly half of all police shootings occur at night, 20/20 acuity is essential for safe and effective job performance. CR: N
Keywords: 355 clinical (human) or epidemiologic studies: risk factor assessment • 353 clinical (human) or epidemiologic studies: outcomes/complications • 584 scene perception