Prototype tests of vertical and torsional alignment nulling for screening vestibular function

BACKGROUND: We have developed a non-invasive, behavioral measure of ocular alignment using a computer tablet, colored lenses, and touch screen software. OBJECTIVE: The goal of this study was to determine if these tests differentiate healthy controls from patients with vestibular disorders. METHODS: In the vertical alignment nulling test (VAN), subjects were asked to adjust a horizontal line that was offset vertically from a fixed horizontal line. In the torsional alignment nulling test (TAN) subjects were asked to adjust a line that was rotationally offset (i.e. clockwise) from a fixed horizontal line. We measured VAN and TAN in 14 healthy controls and 8 patients with known vestibular disorders. RESULTS: Patients had significantly worse scores than controls on TAN, (mean 2.2 vs 0.75, p=0.01), and no differences for scores compared to controls on VAN, (mean 0.4 vs 0.8, p=0.07). CONCLUSIONS: These results suggest that TAN, and possibly VAN, have potential for identifying misalignments in ocular position. After further technical development these tests might be useful in the future for screening patients in facilities that are not equipped to perform cervical and ocular vestibular evoked myogenic potentials.