Dynamic Visual Acuity test while walking or running on treadmill: Reliability and normative data

This study aimed to report normative reference data for a Dynamic Visual Acuity test while walking on treadmill. The protocol's suitability was assessed by investigating its test-retest reliability and its validity through the drop-out rate and verification of the frequency of head movements. Furthermore, the influence of age on visual acuity loss (VAL) was determined to reveal the need for age-specific reference data.

Visual acuity was measured in 171 healthy adult participants (age range: 20.0-77.3 years; mean age: 40.1 years) with the head stationary (SVA) and in a dynamic condition (DVA) while walking on treadmill at 3, 4, 6 and 9 km/h. Relative test-retest reliability on SVA and DVA was investigated with intraclass correlation coefficients (ICC). The measurement errors of SVA, DVA and VAL were calculated for absolute reliability. Influence of age on VAL was investigated with regression analysis, followed by an ANOVA to investigate decade-related differences. The drop-out rate during DVA was mapped using a frequency table. Head frequencies were monitored using 3D motion tracking software.

Strong consistency (ICC ≥ 0.89) was found for SVA and DVA values. Measurement errors for VAL were less than 0.1 logMAR. Younger participants (decade 3-4) showed less VAL at 3 and 4 km/h. The drop-out rate increased with increasing walking speed (0-18.8%), especially in older adults. Although head frequency increased with increasing speed, the dominant frequency ranged around 2 Hz for all walking speeds.

This DVA protocol is reliable and normative data have been established. To facilitate its use in clinical practice, further validation of the protocol in patients with bilateral vestibulopathy is needed.