Prospective assessment of stereoscopic visual status and USAF pilot training attrition

The role of stereopsis (i.e., the use of binocular cues for depth perception) in military aviation is undetermined. Pilots possessing adequate near stereopsis but having deficient distant stereopsis are thought to have microtropias. Historical reviews of microtropia and research concerning the role of depth perception in military aviation are described. A historical prospective study of student pilots entering U.S. Air Force Undergraduate Pilot Training (UPT) from Oct 1990 through Sep 1991 (FY 90-91) compares UPT attrition rates according to their preselection stereoscopic status (microtropia vs. normal). Univariate and multiple logistic regression analyses do not show significant differences in attrition rates between the two groups, implying that distant stereopsis is not critical to successful completion of UPT. The U.S. Air Force decided in Oct 91 to eliminate near stereoscopic vision screening while retaining distant stereoacuity testing as a criterion for candidates to qualify medically for UPT. Valid rationale for this decision includes simplified and uniform administration of stereoacuity testing, minimizing spurious results, the continued validity of stereopsis testing as a cross-check of other areas of visual function, the uncertain role of stereopsis in critical areas of flight operations, and the large applicant pool competing for a limited number of pilot training positions.