耳石—眼反射を用いた耳石器検査法

抄録

Since our visual sense performs its best analysis when images remain steady on the retina, the eyes may need to move in order to track an object. To move the eyes, optokinetic and vestibular reflexes evolved to stabilize images on the retina during head movements. The vestibular and optokinetic systems work together to maintain clear vision during head movements. Because natural head movements occur with high frequency, the visual system is impeded by relatively slow retinal processing (about 70 msec), and cannot adjust rapidly enough to produce compensatory eye movements that would hold images steady on the retina. In contrast, the semicircular-ocular reflex (ScOR) has a latency of less than 16 msec. The ScOR promptly produces slow phase eye movements to compensate for head rotations. The vestibular system also contains otolithic receptors that respond to linear accelerations of the head. The otolith-ocular reflex (OOR) becomes important when head translations cause a slip in the image on the retina. Normally occurring head motion has both rotational and translational components so that both the semicircular canals and otolith organs contribute to the generation of compensatory slow phase eye movements. To evaluate the ScOR, caloric and rotational tests are routinely used. However, there is no practical test of the OOR in clinical use. The development of an otolith function evaluation tool is potentially important, because disorder of the otolith organs may underlie the complaints of some undiagnosed vertigo patients. There are many methods of stimulating the otolith organs, all of which include some form of linear acceleration. In this paper, I will describe a linear sled, eccentric VOR (EVOR) and off-vertical axis rotation (OVAR), which are considered useful and practical methods for evaluating the OOR in clinical practice.