Dynamic Visual Acuity and other Measures of Vision

Abstract

Dynamic Visual Acuity (DVA) is target resolution threshold when there is relative motion between the target and the observer. A slide projector on a turntable throws the target image on a cylindrical screen. The apparatus permits experimental control of target size, angular velocity of target, level of uniformly distributed illumination, monocular vs. binocular viewing of the target, and S's head movement (free vs. fixed). An earlier research report (1) completely describes this apparatus, as well as previously conducted research by others using different apparatus. In the present investigation (one of a series) binocular DVA scores at four target velocities (60, 90, 120, and 15O0/second), taken with either head fixed or head free, were compared with CFF, ACA ratio (a score derived from near and far phoria measurements), and Static Acuity measured on the Bausch and Lomb Ortho-Rater. To facilitate comparison, the DVA targets were projected images of the 15 checkerboards used in the Ortho-Rater acuity test sequence. The 120 Ss (45 male and 75 female, ages 16 to 67) ranged in Static Acuity from 20/15 to 20/40 corrected. Sixty-six Ss were retested with the alternate head movement condition after at least a two-week interval. No evidence was found of a statistically significant correlation between DVA score (at any speed, either fixed-head or free-head) and either ACA ratio or CFF. No evidence was found of a statistically significant correlation between ACA ratio and either CFF or Static Acuity, or between CFF and Static Acuity. Low (from .17 to .31) but significant (p 5 .O5) product-moment correlations were found between DVA and Static Acuity, these correlations decreasing with increasing target velocity and being generally lower for fixedhead DVA than for free-head DVA. Test-retest reliability is .81 for CFF, .82 for ACA ratio, and .77 for Static Acuity (all with p = .001). Lower, but statistically significant reliability coefficients have been found between freehead and fixed-head DVA scores at each speed. Ludvigh and Miller (2) have demonstrated a fairly uniform practice effect in DVA performance. Data being collected will enable the present investigators KO evaluate this practice effect and provide larger samples for reliability analyses for both fixed-head and free-head DVA performance.