A Comparison of Dynamic Vision Between College Athletes & Controls

Subjects move their head at approximately 85 degrees per second per the standard test protocol. A metronome automatically generated by the computer assists in maintaining the correct head speed. When the sensor identifies 85 deg/sec, an optotype appears on the screen and the subject verbally identifies the optotype's orientation. This continues with progressively smaller sized letter until the athlete is no longer able to correctly identify the orientation. The computerized system uses a convergence algorithm to determine the accuracy of the response requiring 3 correct answers at the smallest letter size to assign a result. The computer then compares each subject's DVA score to their SVA, which is expressed a Log of minimal angle resolvable units (LogMAR). Simply, the computer considers the number of lines on an eye chart that are lost with head moving (DVA) compared to the head steady condition, known as static visual acuity (SVA)

The subjects are asked to move their head in the horizontal plane and identify an optotype's orientation at increasing speeds. The optotype remains the same size while the head speed increases. A metronome is utilized to ensure correct head speeds which change throughout the test. When the subject reaches or exceeds the minimum threshold for velocity as measured by a wearable gyroscope attached to the forehead, the optotype appears on the screen for 75 ms, and the subject verbally identifies the direction of the optotype. The subject answers 3 of 5 trials correctly to confirm visual acuity for that velocity. The velocity of head movement begins very slowly (10 deg / second) and the rotational speed increases incrementally as long as the subject is asymptomatic and can see clearly. The test continues until the subject "fails", meaning the subject is unable to answer 3 of 5 trials correctly at a given velocity. The maximum head velocity is measured in degrees/second

The SVA tests the subject's ability to see clearly with their head held still, similar to reading a Snellen eye chart. An optotype is briefly flashed on the screen and the subject is asked to correctly identify its orientation (which directing the capital "E" is facing) as it gets progressively smaller. Once the subject gives an inaccurate answer, the computer ends the test and provides their SVA baseline value based on the smallest optotype they could identify.

Log of minimal angle resolvable units (LogMAR). The number of lines on an eye chart that are lost with head moving (DVA) compared to the head steady condition, known as static visual acuity (SVA)