Dynamic visual acuity using "far" and "near" targets.
CONCLUSIONS
DVA may be useful for assessing the functional consequences of an impaired gaze stabilization mechanism or for testing the effectiveness of a rehabilitation paradigm. Because target distance influences the relative contributions of canal and otolith inputs, the ability to measure DVA at near and far viewing distances may also lead to tests that will independently assess canal and otolith function.


OBJECTIVE
To present and test a methodology that uses dynamic visual acuity (DVA) to assess the efficacy of compensatory gaze mechanisms during a functionally relevant activity that differentially measures canal and otolith function.


METHODS
The effect of treadmill walking at a velocity of 1.79 m/s on subjects' visual acuity was assessed at each of two viewing distances. A custom-written threshold determination program was used to display Landolt C optotypes on a laptop computer screen during a "far" (4 m) target condition and on a micro-display for a "near" (50 cm) target condition. The walking acuity scores for each target distance were normalized by subtracting a corresponding acuity measure obtained while standing still on the treadmill belt.


RESULTS
As predicted by subjective reports of relative target motion, the decrease in visual acuity was significantly greater (p < 0.00001) for the near compared to the far condition.
Peters
Brian T
BT
Neuroscience Laboratory, Wyle Laboratories, Houston, Texas 77058, USA. bpeters@ems.jsc.nasa.gov
Bloomberg
Jacob J
JJ
D000328:Adult; D004215:Distance Perception / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D008297:Male; D008432:Mathematical Computing; D009949:Orientation / Q000502:physiology; D010037:Otolithic Membrane / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D012016:Reference Values; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology; D012984:Software; D014724:Vestibular Function Tests; D014787:Vision Tests; D014792:Visual Acuity / Q000502:physiology*