Abstract
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 (p<0.001). 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.