Abstract
Abstract: :
Purpose: A Bielschowsky head tilt test induces not only an ocular counter-rolling but in addition a combination of horizontal and vertical eye movements. The purpose of this study was to investigate the characteristics of the three dimensional eye movements in response to a head roll with special emphasis on the dynamic changes. Methods: A head roll paradigm was used in 20 healthy subjects. From head straight position the head was rolled to 15, 30 and 45-degree to each shoulder. Each position was held for 10 seconds. The 3D-VOG (Senso Motoric Instruments, Berlin, Germany) was used for three-dimensional recording (25 Hz) of the eye position. The subject was seated 1.5m from a screen displaying a photograph including visual clues to spatial orientation. The VOG mask allowed no vision peripheral to the displayed visual scene. Results: A consistent finding was a fast torsional conjugate eye movement (amplitude 2-8 deg, peak velocity up to 80 deg/sec) in the same direction as the head roll. Without time interval a return movement (peak velocity about 40 deg/sec) towards the initial position was seen followed by an ocular counter-rolling in the opposite direction. Torsional nystagmus beats could be seen superimposed on the return movement. Simultaneously, horizontal conjugate eye movements were seen in the opposite direction to the head movement. The head roll also induced a vertical divergence (amplitude 1-5 deg, peak velocity about 20 deg/sec). Conclusion: The rapid torsional changes in eye position during head tilt presumably stem from the vestibular system and could be explained by inertia of the otoliths. The horizontal and vertical changes in eye position are probably induced by vision in order to maintain fixation on the target and binocular fusion respectively.
Keywords: 618 vestibulo-ocular reflex • 406 eye movements • 589 strabismus: diagnosis and detection