Rotation vectors of slow and quick phase of caloric nystagmus

Abstract Objective The purpose of this study was to elucidate the rotation axes of the slow and quick phase of the caloric nystagmus using the video-oculograhic technique. Methods Subjects were placed in a supine position and cold-water stimulation was applied to the right ear canal. The eye movements were recorded in complete darkness by a high-speed infrared CCD camera. The sampling time of the camera was 132 Hz with 640 × 480 effective pixels. Results The rotation vectors were calculated from the printed-out chart of the 3D analysis data of the caloric nystagmus. The directions of the rotation vector of the quick phase of the nystagmus were almost opposite to those of the slow phase. The average planer equations of the slow and quick phase of the nystagmus in all subjects were 0.399 x + 0.1477 y − 0.8656 z = 0 and −0.3970 x − 0.1940 y + 0.8559 z = 0, respectively. Conclusion We demonstrated that the slow phase and quick phase of the vestibular nystagmus are along with the same axes in human subjects.