Eye Movement Analysis Using Video Images with an Infrared CCD Camera

概要

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It is essential to use an infrared CCD camera in clinical examination of the vestibular system. Devices are currently available that can quite accurately record human eye movements, based on the principle of video-oculography (VOG). We devised an original video-oculography (HI-VOG) system using a commercialized infrared CCD camera, a personal computer and public domain software program (ImageJ) for the data analysis. The video image from the infrared CCD camera was captured at 30 frames per second at a resolution of 640*480 pl.. For analysis of the horizontal and vertical components, the X-Y center of the pupil was calculated using the original macro. For analysis of torsional components, the whole iris pattern, which was rotated by 0.1 degree, was overlaid with the same area of the next iris pattern, and the angle at which both iris patterns showed the greatest match was calculated. For quantitative analysis, the slow phase velocity of each occurrence of nystagmus, the average value of the slow phase velocity and the visual suppression value, were analyzed automatically. Analyses of the eye tracking test, as well as the test for optokinetic nystagmus were also applied in this system. Using the HI-VOG system, it was possible to inexpensively perform nystagmus analysis from video images recorded with an infrared CCD camera.