A software program for the Head Impulse Testing Device (HITD)

The vestibulo-ocular reflex (VOR) uses head angular acceleration information transduced by the semicircular canals in the inner ear in order to drive eye movements that compensate for head rotations, and thus stabilize the visual scene on the retina. Peripheral and central vestibular pathologies may impair the function of the VOR, so that compensation becomes incomplete, making clear vision during head movement impossible. Powerful adaptive mechanisms quickly allow the central nervous system to use residual vestibular information or information provided through other senses to supplement the deficient VOR. Such recovery makes the clinical diagnosis difficult to classical testing techniques, yet the head impulse test allows to reveal vestibular deficits even in adapted patients. A compensatory saccade at the end of the head movement is the clinical sign of a vestibular deficit, and may be spotted by the experienced clinician. Here we describe the rationale and the software program driving a new computerized technique for reliably assessing vestibular function at different head angular accelerations, based on evaluating the ability of the patient in reading a character on the screen while the head is being rotated.