Association of Football Subconcussive Head Impacts With Ocular Near Point of Convergence
Kawata K, Rubin LH, Lee JH, Sim T, Takahagi M, Szwanki V, Bellamy A, Darvish K, Assari S, Henderer JD, Tierney R, Langford D. JAMA Ophthalmol. 2016; ahead of print
Take Home Message: Football players with significant subconcussive impacts had impaired near point convergence before and after full contact practices compared with baseline scores. Football players with less intense head impacts showed no changes over time. Near point convergence may be a useful clinical tool to implement in sports at risk for subconcussive impacts.
Subconcussive head impacts occur more frequently than concussive blows and may cause long-term neurological deficits. However, there are no clinical tools to detect the neurological consequences of subconcussive head impacts within one sport season. Therefore, the authors assessed whether repetitive subconcussive head impacts during preseason collegiate football is associated with changes in near point convergence (a measure of the closest point someone can follow an object coming towards their face). The authors collected head impact kinematic data, near point convergence measurements, and SCAT3 sign and symptom scores during preseason physical examination (June 2015), before and after 1 noncontact and 4 full-contact football training camp practices (3 to 4 days in between), and 3 weeks after the final game. Based on the 5-practice kinematic impact data the authors categorized the athletes into a low impact group (7 athletes) and a high impact group (22 athletes). To measure near point convergence the athlete was seated with the near point convergence ruler placed on the athlete’s upper lip and they focused on a reduced size Snellen chart as it moved toward their face. The near point convergence measurement was taken when the athlete said that the chart went double or the tester observed eye misalignment. There were no differences between impact groups and their demographic data (age, BMI, years of experience, concussion history). Both groups had similar near point convergence at baseline. However, the higher-impact group had greater worsening over time that resolved by the post-season time point. Conversely, the lower-impact group had no change in near point convergence overtime. There was no change in sign and symptom scores between groups or from preseason to post season.
Overall, the authors found that repetitive subconcussive head impacts might compromise near point convergence function without athletes reporting changes in symptoms. However, this only occurred in the high impact group, which was exposed to a greater number and magnitude of impacts. The decline started with the pads-on practices, which is not surprising because this is when contact practices begin. It was alarming to see the decline worsen across the contact practices. Fortunately, these players showed improved near point convergence after a 3-week rest period after the season. This may suggest that ocular-motor function could reflect subclinical brain damage and recovery. It will be interesting to see if future studies confirm these findings, especially among studies that perform baseline testing closer to the start of football training camp practices. Healthcare professionals, athletes, and parents should be aware of the potential harm to the ocular-motor system from subconcussive blows. Though further research is necessary to investigate the clinical relevance, the authors demonstrate that adding a near point convergence measurement to a baseline concussion protocol could be beneficial in assessing subclinical concussions.
Questions for Discussion: Should we be monitoring head impacts? Are you using near point convergence in your concussion protocol? Do you believe these subclinical concussions/subconcussive impacts will cause long-term effects?
Written by: Jane McDevitt, PhD
Reviewed by: Jeff Driban
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