Three-dimensional eye movement recording for clinical application

Methods to measure eye rotations in 3D have developed to a stage where routine clinical application is realistic. Besides the equipment, it requires a basic understanding of 3-dimensional geometry for calibration and interpretation. Relevant parameters are orientation, displacement and thickness of Listing's plane for spontaneous or goal-directed eye movements, and counterrolling or nystagmus with a roll component for vestibular function. The method with the highest temporal and spatial resolution is the magnetic search coil technique. Video-based systems are still slow and cannot be used to characterize saccades. Often, the task of reconstructing the 3-dimensional eye position from a 2-dimensional image of the eye is underestimated. Search coil measurements have shown no firm correlation between the orientation of Listing's plane and "classical" landmarks like stereotaxic head position, emphasizing that Listing's plane is functionally, and not anatomically, determined.