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S. Ramaswamy, J. Hovis; Visual Characteristics of Police Recruits in Ontario . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4331.
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Purpose: Reduced night vision as a complication of refractive surgery has been a concern of agencies which allow refractive surgery procedures in order to meet their uncorrected visual acuity standards. In order to determine whether these concerns are still justified, we evaluated the visual acuity and contrast sensitivity of police recruits and officers attending the Ontario Police College. Methods: Visual acuity and contrast sensitivity was measured for both room illumination and dim illumination. The room illumination test series included high contrast acuity, low contrast acuity and Pelli–Robson contrast sensitivity. The dim illumination test series included high contrast acuity, low contrast acuity, Pelli–Robson contrast sensitivity, license plate number acuity (with and without glare) and the Mesotest. The luminance of the backgrounds in the dim illumination conditions varied from 0.03 to 7 cd/m2. The control group consisted of 85 subjects who wore no–correction (n=60), spectacles (n=19), or contact lenses (n=6) as their habitual correction. The refractive surgery group consisted of 27 subjects who have had LASIK (n=24), PRK (n=2), or RK (n=1). Results: With few exceptions, the general trend in the findings was that the refractive surgery group had a small but significant decrease in visual function. The mean difference on the acuity tasks ranged from 0.02 to 0.04 logMAR units. The exceptions were the Pelli–Robson contrast sensitivity (both light levels), the Mesotest without glare, and high contrast acuity under dim illumination where there were no significant differences between groups. The other trend in the data was that poorer performing refractive surgery subjects fell outside the range of the control group. Conclusions:Although there were significant differences between the control and refractive surgery groups, the mean difference was small and unlikely to have any practical impact on performance. Nevertheless, there was a small number (approximately 10%) of individuals who fell outside the control group’s range. This latter finding suggests that candidates who have undergone refractive surgery should be screened for potential night vision problems.
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