Increased retinal image velocity after vestibular lesion

The vestibule-ocular reflex stabilizes gaze during head movements by produc ing compensatory eye movements. Retinal image velocity (RIV) is defined as the difference between the eye and head velocities. The RIV of 20 vestibula r schwannoma (VS) patients and 17 healthy controls was measured with a head autorotation test. The head autorotation test had a sensitivity of 80% and a specificity of 88%. The mean RIV (degree/second) +/- 95% confidence inte rvals of the VS patients in the 5 frequency bands of 1 to 5 Hz was respecti vely 4.8 (4.2 to 5.5), 11.5 (8.6 to 14.4), 21.7 (15.5 to 27.9), 25.2 (17.1 to 33.4), and 26.1 (13.1 to 39.1). The RIV of the VS patients was asymmetri cally larger on the operated side (P < 0.05) in the frequency band of 1 Hz. The mean RIV was significantly (P < 0.05) larger in the VS patients than i n the controls in the frequency bands of 1. to 4 Hz. The vestibule-ocular r eflex is inaccurate after VS surgery; but the inaccuracy may not lead to th e occurrence of any symptoms.