The effects of drift and displacement motion on Dynamic Visual Acuity

RESUMEN

Dynamic Visual Acuity (DVA) can be measured from two types ofequivalently considered movement referred to as drifting-motion anddisplacement-motion. Displacement motion can be best described as thehorizontal displacement of a stimulus, thus implying pursuit eyemovements, and involves moving the stimulus from the fixation point ofgaze towards the periphery. The drifting motion of a Gabor patch, forexample, avoids pursuit eye movements, since the gaze is fixed in a point ofthe patch. Our data shows that in both types of movement visual acuity(VA), expressed in terms of spatial frequency, diminished as the velocity ofthe target increased. However, the slope of the regression equation indicatedthat this impairment is more than two-fold in the case of drifting-motionwhen compared to displacement motion. As the greater impairment tookplace when pursuit eye movements did not exist, our data suggests that thesetwo types of motions correct differently for retinal slip. Retinal slip appearsto be less efficiently compensated for in the case of drifting motion havingadverse consequences on VA, while retinal slip has a higher tolerance in thecase of displacement motion exhibited by the performance in VA