Is horizontal semicircular canal ocular reflex influenced by otolith organs input?

CONCLUSION

Otolith organs input influences the axis of horizontal semicircular canal ocular reflex; therefore, the plane of compensatory eye movements induced by the horizontal canal stimulation is not always parallel to the canal.

OBJECTIVE

To clarify whether horizontal canal ocular reflex is influenced by otolith organs input.

METHODS

The subjects were seven healthy humans. The right ear was stimulated using ice-water. Each subject was kept in a left-ear-down position for 20 s and then repositioned to a prone position, a right-ear-down position and a supine position with 20 s intervals. Nystagmus was analysed using three-dimensional video-oculography.

RESULTS

Eye movements in the supine position and the prone position were not in a symmetric fashion. Nystagmus in the left-ear-down position and the right-ear-down position were not symmetric either. These phenomena indicate that the axis of the eyeball rotation was affected by the shift of the direction of gravity exerted on the head.