Abstract
To clarify the effect of head motion on dynamic visual acuity (DVA), we analyzed the relationship between DVA and eye movements during sinusoidal passive head translation at 0.6-1.4 Hz (amplitude: 5 cm) along the inter-aural axis using our original linear sled. Five healthy subjects were asked to read aloud sets of three numbers presented on a CRT monitor at a 30 cm distance that moved sinusoidally at the same frequency (amplitude: 7.5 cm) in the opposite direction to the head. We evaluated the percentage of correct answers as an index of DVA. For comparison, control experiments were conducted while the head was stationary. The main results showed that DVA improved significantly during head translation compared to when the head was stationary at 1.4 Hz (paired t-test, p<0.05). Although head translation did not affect DVA at 0.6-1.2 Hz. At 1.4 Hz, the vestibuloocular reflex evoked by head translation increased tracking gain, decreased phase-lag, and suppressed catch-up saccades. Consequently, gaze velocity (eye velocity in space) was bigger with head translation versus a stationary head. In addition, we identified another DVA-determining factor that was independent of head translation and eye movements. We consider that these composite factors improve DVA during higher-frequency head translation.
