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JAMA Ophthalmol. 2016 Jul 1;134(7):763-9. doi: 10.1001/jamaophthalmol.2016.1085.

Association of Football Subconcussive Head Impacts With Ocular Near Point of Convergence.

Author information

1
Department of Neuroscience, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania2Department of Kinesiology, Temple University, Philadelphia, Pennsylvania.
2
Department of Psychiatry, University of Illinois at Chicago.
3
Department of Neuroscience, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania.
4
Department of Kinesiology, Temple University, Philadelphia, Pennsylvania.
5
Department of Athletics, Temple University, Philadelphia, Pennsylvania.
6
Department of Mechanical Engineering, Temple University, Philadelphia, Pennsylvania.
7
Department of Ophthalmology, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania.

Abstract

IMPORTANCE:

An increased understanding of the relationship between subconcussive head impacts and near point of convergence (NPC) ocular-motor function may be useful in delineating traumatic brain injury.

OBJECTIVE:

To investigate whether repetitive subconcussive head impacts during preseason football practice cause changes in NPC.

DESIGN, SETTING, AND PARTICIPANTS:

This prospective, observational study of 29 National Collegiate Athletic Association Division I football players included baseline and preseason practices (1 noncontact and 4 contact), and postseason follow-up and outcome measures were obtained for each time. An accelerometer-embedded mouthguard measured head impact kinematics. Based on the sum of head impacts from all 5 practices, players were categorized into lower (n = 7) or higher (n = 22) impact groups.

EXPOSURES:

Players participated in regular practices, and all head impacts greater than 10g from the 5 practices were recorded using the i1Biometerics Vector mouthguard (i1 Biometrics Inc).

MAIN OUTCOMES AND MEASURES:

Near point of convergence measures and symptom scores.

RESULTS:

A total of 1193 head impacts were recorded from 5 training camp practices in the 29 collegiate football players; 22 were categorized into the higher-impact group and 7 into the lower-impact group. There were significant differences in head impact kinematics between lower- and higher-impact groups (number of impacts, 6 vs 41 [lower impact minus higher impact = 35; 95% CI, 21-51; P < .001]; linear acceleration, 99g vs 1112g [lower impact minus higher impact= 1013; 95% CI, 621 - 1578; P < .001]; angular acceleration, 7589 radian/s2 vs 65 016 radian/s2 [lower impact minus higher impact= 57 427; 95% CI , 31 123-80 498; P < .001], respectively). The trajectory and cumulative burden of subconcussive impacts on NPC differed by group (F for group × linear trend1, 238 = 12.14, P < .001 and F for group × quadratic trend1, 238 = 12.97, P < .001). In the higher-impact group, there was a linear increase in NPC over time (B for linear trend, unstandardized coefficient [SE]:  0.76 [0.12], P < .001) that plateaued and resolved by postseason follow-up (B for quadratic trend [SE]: -0.06 [0.008], P < .001). In the lower-impact group, there was no change in NPC over time. Group differences were first observed after the first contact practice and remained until the final full-gear practice. No group differences were observed postseason follow-up. There were no differences in symptom scores between groups over time.

CONCLUSIONS AND RELEVANCE:

Although asymptomatic, these data suggest that repetitive subconcussive head impacts were associated with changes in NPC. The increase in NPC highlights the vulnerability and slow recovery of the ocular-motor system following subconcussive head impacts. Changes in NPC may become a useful clinical tool in deciphering brain injury severity.

[Indexed for MEDLINE]

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