Roles of head, gaze, and spatial orientation in the production of oscillopsia.

To clarify the factors causing oscillopsia, we investigated head movement, gaze stability, and perception under various situations. High-frequency head movements, whether they were horizontal rotations or passively induced vertical oscillations, produced blurred vision and gaze fluctuations in patients with labyrinthine loss. However, this sensation differed from the oscillopsia perceived during walking, as it did not involve a sensation of oscillation of the surrounding space or a loss of body balance. Although patients with labyrinthine loss showed large irregular head perturbations during stepping, the resultant retinal velocity slips seemed too small to explain oscillopsia. Walking while wearing horizontal reversing prisms produced loss of spatial orientation, dysequilibrium, and instability of vision in normal subjects, which resembled the symptoms found in patients with oscillopsia. The present study suggests that oscillopsia represents a perceptual inability to detect spatial orientation during head or body movements rather than a mere blurring of vision caused by deficient compensation.