Comparison of the gaze stabilization test and the dynamic visual acuity test in unilateral vestibular loss patients and controls

Objective: Compare the dynamic visual acuity test (DVAT) and gaze stabilization test (GST) in patients with unilateral vestibular loss (UVL) and healthy control subjects using a novel computerized testing system prototype. Study Design: Cross-sectional study. Setting: Tertiary academic referral laboratory. Patients: Seventeen UVL patients (median age 62 yr) with bithermal caloric asymmetry (≥49%) or ablative surgery and 17 control subjects (median age 57 yr). Intervention(s): Diagnostic. Main Outcome Measure(s): Comparison of DVAT and GST results during self-generated sinusoidal head movements using transient unpredictable target presentations less than 95 milliseconds in duration. Results: UVL patients had significantly higher DVAT scores toward the lesioned side compared with controls (p = 0.001) and the non-lesioned side (p = 0.003), but the non-lesioned side was not significantly different from controls (p = 0.157). When comparing GST scores, UVL patients required a slower head velocity to maintain visual acuity with movement toward the lesioned side compared with controls (p < 0.001) and the non-lesioned side (p = 0.004). In addition, UVL patients had significantly lower scores toward the non-lesioned side (p = 0.002) compared to controls. ROC curve analysis identified optimal thresholds for abnormal test results to discriminate the lesioned side from controls. A DVAT score greater than or equal to 0.3 ΔlogMAR provided 65% sensitivity and 88% specificity while a GST score less than or equal to 95 degrees/s provided 71% sensitivity and 100% specificity. When GST results were normal, adding DVAT increased overall sensitivity to 88% with 88% specificity. Conclusions: Both GST and DVAT demonstrated reduced gaze stabilization toward the lesioned side in the patient group compared with normal controls. Performing GST first and utilizing DVAT when GST was normal provides optimal identification of patients with vestibular dysfunction.