DVA Test (Standing DVA and loDVA)

The SVA and DVA tests were measured by repeatedly displaying one optotype at a time when the subject was walking and reading optotypes with head turning at 2 Hz. The patient first performed the SVA test on either side without any head movement as the baseline. Then, they performed the DVA test with head turning while standing or walking. The subject was asked to state the orientation of the “E” letters shown on the screen in front of them. Once a subject gave researchers an oral response, the researcher keyed in the answer for judgment by the program and the next trial started. In the DVA test, when the head velocity measured by the IMU on the top of head was >120 degrees/second, the system displayed the optotype “E” in a random sequence of orientations (0, 90, 180, or 270°) on the monitor for 75 ms. The monitor displayed one randomly oriented optotype 5 times for each optotype size, and the optotype size decreased in steps equivalent to a visual acuity difference of 0.1 logMAR. The 0.1 logMAR is the minimum angle resolved, in arcmin, with 1 arcmin equal to 1/60°. The converter of optotypes was equivalent to the Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity chart. After all tests, the DVA result was calculated by subtracting the correct answers in the static visual acuity test from those in the dynamic visual acuity test. The missed optotypes between the DVA and SVA were converted to the decimal visual acuity LogMAR, which comprises 11 levels ranging from 20/20 to 20/200 in vision. There were 11 lines/sizes (5 optotypes per size) in the test for each side. If the subject missed all optotypes of the same size or provided responses for all 55 optotypes in our test, they had to terminate the trial. Additional information on the visual acuity computations has been published elsewhere (38, 39). In the DVA test, the initial test size level was set to 4 levels above the smallest results in the SVA test.