Effect of viewing distance on dynamic visual acuity.

Abstract

BackgroundPatients with dizziness and unsteadiness are commonly prescribed gaze stability exercises at varying target distances to manage vestibular impairments but lack objective tools to monitor progress. Maintaining gaze stability during head motion at near distances demands greater eye velocity relative to head velocity due to vergence and increased translational eye rotation demands.ObjectivesThis study compared dynamic visual acuity (DVA) during yaw and pitch at both near and far distances in patients and healthy controls.MethodsThis study includes individuals with unilateral vestibular deafferentation (UVD), veterans with dizziness yet healthy vestibular function, and healthy controls. The computerized DVA at near (50 cm) and far (200 cm) distances were collected. Data analysis included comparisons of near and far DVA in yaw and pitch planes.ResultsA total of 94 participants (34 UVD, 24 veterans with dizziness, 36 controls) were included. Near-distance DVA was significantly worse than far-distance DVA for the entire sample and within each group (p < 0.001).ConclusionsNear-distance DVA is more challenging than far-distance DVA across populations and planes of head rotation. Near-distance DVA may serve as a robust measure of vestibulo-ocular reflex function and offers a practical means for patients to self-monitor the effects of gaze stability training.