A Comparison of Stereoacuity at 6m of Collegiate Baseball Players in Primary Gaze and Batting Stance

摘要

INTRODUCTION Accurate discrimination of distance information and judgments of spatial localization may be advantageous during baseball batting. Stereopsis is traditionally measured in primary gaze, however a baseball batter's eyes are typically in a lateral gaze direction during batting. The purpose of this study was to compare stereopsis performance at far in primary gaze and in preferred batting stance in a population of collegiate baseball players. METHODS Measurements of 6m stereoacuity were conducted as part of a visual performance assessment for the Pacific University men's baseball team (NCAA Division III) from 2004 to 2009. The athletes were 18-24 years of age (N=149), and only measurements taken during their first season's participation were used for analysis in returning athletes. Threshold stereoacuity was measured using a 2-forced choice paradigm at pre-set rod separations with a Howard-Dolman device. Threshold stereoacuity was subsequently measured with the athlete in preferred batting stance. RESULTS The mean threshold stereoacuity in primary gaze was significantly better than in batting stance (p0.001). The difference in the mean thresholds (8.38 vs 9.92 arc sec) was not considered clinically significant due to the magnitude of the stereoacuity intervals measured. The majority (59%) of athletes maintained the same stereoacuity threshold in both primary gaze and batting stance. A significant number of athletes (32%) performed worse in batting stance compared to primary gaze, while a small number performed better in batting stance (9%). DISCUSSION There is a statistically significant reduction in 6m stereoacuity when measuring collegiate baseball players in batting stance compared to primary gaze position. Many athletes maintain the same stereoacuity threshold in batting stance, however a significant number demonstrated a reduction in depth sensitivity to real-space depth targets. To determine if depth sensitivity may affect baseball batting, depth perception should be assessed in both primary gaze and batting stance.