Abstract
INTRODUCTION: The ability to perceive depth information is critical to athletes during competition - to localize, track and react to objects, teammates, and opponents. Traditionally, stereopsis is measured at near distance and measured along the normal line of sight (primary gaze). The purpose of this study was to compare primary to non-primary stereoacuity at far in athletes.
METHODS: Stereoacuity was measured to a higher threshold than traditionally assessed, and was part of a comprehensive visual performance evaluation. One hundred thirteen athletes, age 12 to 38 years, were evaluated at sports performance training centers and optometric practices. Four Wirt-type circles were presented, with one circle having stereoscopic float induced by lateral disparity, ranging from 240 to 12 arsec. Circles were displayed on a high frequency computer monitor synchronized with active shutter eyewear at 4.9 m. Utilizing a staircase algorithm, subjects responded in a 4-choice forced-choice paradigm to determine threshold. Stereoacuity was measured in primary gaze and two non-primary gazes (head turned with gaze over the right shoulder and then over the left shoulder).
RESULTS: Average (sd) stereoacuity thresholds were 27.5 (62.4) arcsec in primary gaze, 46.8 (28.9) arcsec in left gaze and 42.2 (42.5) arcsec in right gaze. Repeated measures analysis of variance showed that primary gaze stereoacuity was significantly better than non-primary gaze over the left shoulder (p = 0.0059) and right shoulder (p = 0.0499). Sixty-one percent (69 of 113) of the subjects demonstrated reduced stereoacuity in at least one non-primary gaze angle.
DISCUSSION: Considering the widely varying visual gaze demands athletes face in most sports, when assessing an athlete's stereoacuity, primary and non-primary gaze angles should be measured. Considering the average stereoacuity was 27.5 arcsec, with best being 12 arcsec, test methods should be more sensitive to determine stereoacuity threshold for athletes.