VOGによる眼球運動三次元軸解析

抄録

Recently, eye movement is represented by the axis angle, rotation vector, or quaternions, not by Fick coordinates. The axis angle, rotation vector, and quaternions measure single axis rotation from a chosen reference position to the current eye position. Using the axis angle, rotation vector, or quarternions, we can represent the eye position and eye velocity in the same three-dimensional coordinate. Using the axis angle, rotation vector, or quarternions, we can calculate the axis around which the eye rotates. We can also calculate the angular velocity around the axis. In this review, using the axis angle, rotation vector, or quarternions, we show that the gain of the vestibule-ocular reflex (VOR gain) around the eye rotational axis can be calculated both when lateral semicircular canals are mainly stimulated and when vertical semicircular canals are mainly stimulated. We calculated this VOR gain of patients with horizontal canal-type or posterior semicircular canal-type benign paroxysmal positional vertigo (BPPV). As a result, cupulolithiasis in semicircular canals affected the dynamics of the VOR at 0.1 Hz, but not at higher frequencies, and canalolithiasis in semicircular canals does not change the VOR gain at any frequencies. We also show that we can identity the affected lesion of semicircular canals by calculating the axis of positional nystagmus in BPPV patients. Posterior canal-type BPPV caused positional nystagmus of which the rotational axis was perpendicular to the plane of the posterior semicircular canal or pure torsional axis. Anterior semicircular canal-type BPPV caused positional nystagmus of which the eye rotational axis was perpendicular to the plane of the anterior semicircular canal. BPPV due to the simultaneous involvement of both horizontal and posterior semicircular canals had two rotational axes; at first it was perpendicular to the plane of the posterior semicircular canal, and next, it was perpendicular to the plane of the horizontal semicircular canal.