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A Method to Monitor Eye and Head Tracking Movements in College Baseball Players

Fogt, Nicklaus F.*; Zimmerman, Aaron B.


The article, A Method to Monitor Eye and Head Tracking Movements in College Baseball Players, which appeared in the February 2014 issue of Optometry and Vision Science, regretfully contained an error. Some blink-related artifacts were included in the eye movement data late in the pitch (between 342 milliseconds and 382 milliseconds). Many of these were from subject 11. In Table 4 at 342 milliseconds, for subject 11 the corrected mean head movement, mean eye movement, and mean signed gaze error (GE) was 6.7 ± 1.4°, 8.3 ± 1.5°, and 2.2 ± 1.7°, respectively. The corrected regression equations (all subjects) from Table 5 at 342 milliseconds were -11.1 + 0.6 (head) (r2 = 0.31, p < 0.001) (GE) and 10.1–0.3 (head) (r2 = 0.13, p < 0.001) (unsigned gaze error [UGE]), and at 382 milliseconds were -81.5 + 1.1( head) (r2 = 0.63, p < 0.001) (GE) and 81.5–1.1(head) (r2 = 0.63, p < 0.001) (UGE). Shown below are Table 3 (corrections >1.1° in bold) and Figure 8 (corrected at 342 milliseconds and 382 milliseconds).

Optometry and Vision Science. 91(9):e253, September 2014.

doi: 10.1097/OPX.0000000000000148
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Purpose This study had two purposes. The first was to develop a method to measure horizontal gaze tracking errors (based on synchronized eye and head tracking recordings) as subjects viewed many pitched balls. The second was to assess horizontal eye, head, and gaze tracking strategies of a group of Division 1 college baseball players.

Methods Subjects viewed, but did not swing a bat at, tennis balls projected by a pneumatic pitching machine. Subjects were to call out numbers and the color of these numbers (black or red) on the balls. The trajectory of each pitch was very predictable. Eye and head movements were monitored with a video eye tracker and an inertial sensor, respectively, and these movements were synchronized with ball position using an analog recording device. Data were analyzed for 15 subjects.

Results Eye rotation, head rotation, gaze errors (GEs), and unsigned gaze errors (UGEs) were calculated at various elapsed times. On average, subjects tracked the pitched ball with the head throughout the pitch trajectory, while the eye was moved very little until late in the pitch trajectory. On average, gaze position matched the target position throughout the pitch trajectory. There was some variability in the mean amplitudes of head and eye movement between subjects. However, the eye and head were related by a common rule (partial rotational vestibulo-ocular reflex suppression) for all subjects. Although the mean amplitudes of the GE and UGE varied between subjects, these means were not consistent with anticipatory saccades for any subject.

Conclusions On average, Division 1 college players tracked the pitched ball primarily with the head and maintained gaze close to the ball throughout much of the pitch trajectory. There was variability between subjects regarding the head and eye movement amplitudes and GEs, but, overall, all subjects maintained gaze close to the ball throughout the pitch trajectory despite the fact that these individuals were not batting.



The Ohio State University College of Optometry, Columbus, Ohio (NFF, ABZ); and The Department of Ophthalmology, Nationwide Children’s Hospital, Columbus, Ohio (NFF).

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (

Aaron B. Zimmerman The Ohio State University College of Optometry 338 West 10th Ave Columbus, Ohio 43210 e-mail:

© 2014 American Academy of Optometry