The subject is assigned a score based on the contrast of the last group in which two or three letters were correctly read. Which of the following is NOT an advantage of using visuals during a presentation? How are slides most effectively used during a presentation? Mean deviation (MD) on the Humphrey Field Analyzer and mean defect (MD) on the Octopus perimeter represent the average overall deviation of visual field sensitivity from normal for the central 30 radius of the visual field. Specific recommendations for visual acuity chart design and testing conditions have been made by several bodies (American National Standards Institute International Standards, 1986a, 1986b; Consilium Ophthalmologicum Universale Visual Functions Committee, 1988; National Research Council, 1980, 1994). Table 2-1 presents these alternative forms of measurement as a conversion table. Also, since letters contain many orientations, it is not strongly dependent on a particular orientation, as the Vistech chart is. Snell and Sterling found experimentally that to reduce normal (20/20) acuity to qualitative vision (no useful resolving power) required six times the diffusing strength needed to reduce 20/20 acuity to 20/40, so they proposed that 20/40 vision represented a one-sixth (16.7 percent) loss of visual efficiency. A description of the commonly used color vision tests is available in Pokorny et al. There is no agreed-on standardization of glare recovery testing in terms of such factors as glare intensity, time, and type and size of target used. These two charts were found acceptable in the 1994 Committee on Vision report (National Research Council, 1994). Eye Movements and Their Functions in Everyday Tasks, The Causes and Consequences of Color Vision. We therefore recommend that research be undertaken to establish the distributions of our recommended measures of acuity, fields, and contrast sensitivity in the working-age population. Loss of vision in one eye does not appear to affect the performance of drivers in test maneuvers (McKnight et al., 1991; Wood & Troutbeck, 1992; Wood et al., 1993), but it has been found in some studies to elevate crash risk (Laberge-Nadeau et al., 1996; Maag et al., 1997; Rogers, Ratz, & Janke, 1987). The 2001 AMA guide now recommends using a weighted combination of binocular, right eye, and left eye acuity scores to calculate an acuity-related impairment rating: Visual impairment ratings are calculated using the formula (3OU + OD + OS)/5 instead of the prior formula (3 better eye + 1 lesser eye)/4.
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