Score for leftward rotation difference logMAR, as part of the NIH Toolbox Sensation Domain Vestibular Measure Dynamic Visual Acuity Test

The NIH Toolbox Dynamic Visual Acuity Test (DVA) is a measure of gaze stability during head movement, which helps identify individuals who may have a deficit of the vestibular system (which regulates internal balance). First, the NIH Toolbox Visual Acuity Test must be administered, followed by the DVA Test. Participants are again seated 12.5 feet from a computer monitor at eye level. For the DVA Test, participants wear lightweight headgear that contains a rate sensor and are asked to move the head back and forth, as if saying no. Once the head is measured to be moving at greater than 180 degrees per second by the rate sensor, an optotype flashes on the monitor, and the participant is asked to identify it. As with the Visual Acuity Test, only the letters H, O, T, and V are used for ages 3 to 7 while ages 8+ use the entire letter set. Smaller optotypes are displayed as the participant correctly identifies letters, and larger ones are displayed if the participant cannot correctly identify the letter shown, until the computer has calculated the smallest size that the participant can see with the head moving. This is calculated separately for head rotation leftward and rightward from center (though the participant continues shaking the head both ways), and this performance is compared to the participants visual acuity when the head was stationary (the NIH Toolbox Visual Acuity Test 16 score, sometimes referred to as static visual acuity in the context of the DVA test). The difference between static and dynamic visual acuity represents the vestibular contribution to gaze stability. The DVA Test takes approximately six minutes to administer and is recommended for ages 3-85.

2016-06-03

http://www.nihtoolbox.org/WhatAndWhy/Sensation/Vestibular/Pages/NIH-Toolbox-Dynamic-Visual-Acuity-Test-.aspx

Visual Acuity Score minus DVA Leftward Rotation Score, converted to LogMAR units.form. A LogMAR score can be calculated from the raw number correct score using the following equation: LogMAR score = 1.7 (0.02*RAW). The MAR (minimum angle of resolution) is the reciprocal of the Snellen score notation. It equals the angle (in minutes of arc) at which the strokes of the letter subtend at the examinees eye.