OCULOMOTOR FUNCTION IN ADOLESCENT ATHLETES FOLLOWING CONCUSSION

Abstract

Background:Visual impairments affect up to 90% of patients post-concussion. These impairments may include deficits in fixation accuracy, smooth pursuit, saccadic latencies, vergence, accommodation, and vestibule-ocular reflexes. Quantitative assessment of oculomotor function may provide a sensitive and objective measure of concussion diagnosis and recovery since coordinated eye movements require the use of diverse and widely dispersed areas of the brain. This study quantified oculomotor function over time in adolescents following concussion.Hypothesis/Purpose:We hypothesized that adolescent concussion patients would demonstrate deficits of oculomotor function that would resolve by the time of return to play (RTP) and remain stable after RTP.Methods:13 adolescent athletes diagnosed with mild to moderate concussion (7 male; mean age 15.1, SD 2.1, range 10-17 years) were prospectively evaluated at their initial visit (mean 18, range 4-43 days post-concussion), at the time of clearance to RTP (mean 46, range 12-173 days post-concussion), and one month later (mean 26, range 20-41 days after RTP). 11 controls without past concussion or injury (3 male; mean age 12.3, SD 3.1, range 8-17 years) were also tested at similar time points. Eye tracking was recorded as participants followed a target moving on a screen in predefined patterns related to sinusoid and trapezoid smooth pursuit, vergence, saccade, and anti-saccade. Metrics characterizing the speed, accuracy, and variability of tracking were compared between groups and visits using t-tests and linear mixed-effects regression.Results:At their initial visit, patients tended to have greater overshoot and greater variability in tracking compared with controls (Table 1.1). Overshoot and variability of tracking during sinusoid smooth pursuit (both overall variability and variability of overshoot) decreased from initial visit to RTP (Table 1.2). Undershoot during sinusoid smooth pursuit tended to decrease from RTP to 1-month follow-up. The rate of convergence in the distance vergence task increased while the rate of divergence decreased between these time points.Conclusion:The main oculomotor deficits observed in concussed adolescents related to overshoot and variability of tracking during sinusoid smooth pursuit. These deficits resolved by the time of RTP and generally remained stable or continued improving after RTP. These results suggest that oculomotor function recovers sufficiently under current conservative treatment protocols.Table 1.1.Comparison of concussed patients at initial visit vs. controls ConcussedInitial VisitMean (SD)Control Mean (SD)p-valueSaccade latency0.44 (0.07)0.45 (0.07)0.72Anti-saccade latency0.65 (0.12)0.62 (0.08)0.41Rate of convergence1.44 (0.31)1.51 (0.25)0.62Rate of divergence1.56 (0.17)1.55 (0.24)0.94Sinusoid peak phase lag10.40 (6.75)10.55 (1.80)0.95 Sinusoid mean SD of error 3.19 (1.95) 2.00 (0.91) 0.075 Sinusoid mean overshoot 4.72 (4.23) 2.16 (1.54) 0.075 Sinusoid mean undershoot3.07 (0.91)2.90 (0.29)0.57Sinusoid SD overshoot5.17 (4.84)2.30 (1.80)0.080Sinusoid SD undershoot3.35 (1.11)3.28 (0.38)0.83Sinusoid smooth pursuit involves a target moving in a sinusoidal pattern in a horizontal direction. A full period of movement covers 35.6 degrees over 2.4 seconds.Table 1.2.Change between visits for patients Coef (SE)RTP vs. IVp-valueCoef (SE)Follow-up vs. RTPp-valueSaccade latency0.008 (0.022)0.739-0.034 (0.023)0.139Anti-saccade latency-0.015 (0.045)0.729-0.069 (0.050)0.166Rate of convergence-0.073 (0.088)0.410 0.269 (0.097) 0.005 Rate of divergence-0.021 (0.154)0.889 -0.315 (0.172) 0.068 Sinusoid peak phase lag1.52 (1.97)0.441-1.88 (2.05)0.359Sinusoid mean SD of error -1.04 (0.53) 0.048 0.49 (0.52)0.348Sinusoid mean overshoot -1.97 (0.98) 0.045 0.43 (0.97)0.657Sinusoid mean undershoot-0.02 (0.10)0.818 -0.16 (0.09) 0.080 Sinusoid SD overshoot -2.59 (1.04) 0.013 0.86 (1.02)0.396Sinusoid SD undershoot-0.17 (0.29)0.5690.15 (0.29)0.610Sinusoid smooth pursuit involves a target moving in a sinusoidal pattern in a horizontal direction. A full period of movement covers 35.6 degrees over 2.4 seconds.