Vestibular Autorotation Test (VAT)
The Vestibular Autorotation Test (VAT) is a computerized test of head and eye movements to evaluate both the high frequency horizontal and vertical vestibulo-ocular reflex (VOR). The VOR system stabilizes fixation of the eyes during head rotation by causing the eyes to move in the opposite direction of the head motion. The main purpose of the VOR is to allow clear vision during movement by sending signals to move the eye muscles to compensate for the small rapid head movements that occur in everyday life. However if the speed or timing is off, even slightly, vision is distorted because of apparent movement of the visual fields. The VAT tests the normal, everyday range of head motion where many balance disorders occur. The computer analyzes head motion and simultaneous eye movements. Electrodes record eye movement while a velocity head sensor records head movement. The VAT is used in the diagnosis of inner ear disturbances and also to monitor changes during vestibular rehabilitation. The VAT is comfortable and easy to perform. You are asked to look at the target and move your head to the computer-generated tone. The tone begins slowly and becomes increasingly faster over an 18-second period.