Clinical Research Directory

First, participants will report the direction of the open portion of a "Landolt C" (right, left, up, or down) with the head still. Ten targets at 5 acuity levels (LogMAR -0.3, 0, 0.3, 0.7, 1.0, corresponding to Snellen visual acuity of 20/10, 20/20, 20/40, 20/100, 20/200) will be identified. Next, a rate sensor will be placed on the subject's head in the plane of the horizontal canals and htDVA will be measured. The "Landolt C" will be presented automatically when the examiner has moved the subject's head \> 150˚/sec. htDVA scores will be the LogMAR at which the subject fails to correctly identify 50% of the visual targets or reaches a LogMAR of -0.3. The overall htDVA score is calculated by subtracting the head still LogMAR from the htDVA LogMAR. htDVA scores will be calculated for right and left head movements separately.

The TOSWRF will be used to assess reading fluency. Children get 3 minutes to identify as many words as possible by drawing boundaries between successive unrelated words. The TOSCRF will be used to assess reading fluency. Children are allowed 3 minutes to identify as many contextually related words as possible by drawing boundaries between successive words. The TILLS will be used to assess reading comprehension. Each subject will read a short passage and answer 3 yes/no questions assessing reading comprehension. A computer based MNREAD Test will be used to assess reading acuity, critical print size and Reading Accessibility Index. During the TILLS and MNRead test, eye tracking (Eye Link 1000+ eye tracker) will be used to record fixation duration, saccade length, regression frequency, and total time spent.

The subject's head will be in a headrest. Static visual acuity will be assessed in 9 domains (3 levels of visual target complexity x 3 levels of presentation complexity). The 3 levels of visual target complexity are identifying: 1) colors, 2) the direction of the open prongs of the "Landolt C" (right, left, up, or down), which does not require alphabet knowledge, and 3) single letters (C, D, H, K, O, N, S, R, V, and Z; NIH Toolbox, Li 2014)). The 3 levels of presentation complexity are identifying: 1) 1-visual optotype, 2) a successive row of 5 visual optotypes flashed for 3 seconds (Hillman 1999), and 3) successive rows of optotypes in paragraph form as quickly as possible (i.e., rapid automatized naming). Outcome parameters will be %-correct at each acuity level and reaction time. Fixation duration, saccade length, saccade frequency, regression frequency, and total time spent will be collected via an eye tracker (Eye Link 1000+ eye tracker \[SR Research, EyeLink, Ontario, Canada\]).