Blink reflex parameters in baseline, active, and head-impact Division I athletes

Figures & data

Figure 1. Blink reflexometer housing unit and software interface. Tubing connected to the left end of the housing unit delivers a puff of compressed air to the subject’s eyes.

Figure 2. Illustrations of time-displacement profiles of upper lid movement during and after a stimulated blink. (A) Baseline blink reflex time-displacement profile. (B) Blink reflex time-displacement profile after active play. Latency is increased. Differential latency is decreased. Log of number of oscillations is less. (C) Blink reflex time-displacement profile after a head impact causing a concussive event. Latency is decreased. Differential latency is increased. Log of number of oscillations is increased.

Note: Figures are not drawn to scale and changes are amplified for visibility.

Figure 3. Blink reflex parameter changes from baseline due to active play or head impact.

Notes: A positive slope indicates that the second measurement was increased on average relative to the baseline measurement. A negative slope indicates that the second measurement decreased relative to the baseline measurement. Black lines represent the mean values for control athletes at baseline and with activity and red lines represent the mean values for head impacted athletes at baseline and after head impact during activity. p-values are for the difference in the change in blink parameter between rest and activity between Control and Head Impacted athletes.

Table 1. Estimated mean differences (and standard errors) within and between groups

	Control athletes				Head impacted athletes				Head impact vs. active
Blink parameter	Baseline	Active	Baseline vs. active	p1	Baseline	Post-impact	Baseline vs. post-impact	p2	Delta difference	p3
Latency (msec)	50.2 (2.58)	55.9 (2.85)	−5.67 (1.45)	<0.001	54.2 (2.30)	51.9 (2.46)	2.23 (1.01)	0.028	−7.89 (1.80)	<0.001
Differential latency (msec)	6.93 (0.44)	5.43 (0.68)	1.50 (0.63)	0.017	6.21 (0.37)	7.61 (0.51)	−1.40 (0.40)	<0.001	2.90 (0.74)	<0.001
Delta 30	5.13 (0.64)	4.41 (0.48)	0.72 (1.15)	0.533	4.18 (0.52)	4.01 (0.87)	0.18 (0.83)	0.835	0.56 (1.45)	0.698
Eyelid excursions (pixels)	146.2 (6.18)	138.3 (7.02)	7.86 (4.03)	0.052	137.0 (5.55)	140.0 (6.06)	−2.96 (2.86)	0.302	10.8 (5.06)	0.033
Lid Velocity (pixels/msec)	3.83 (0.15)	3.56 (0.17)	0.28 (0.098)	0.005	3.60 (0.14)	3.53 (0.15)	0.07 (0.07)	0.276	0.21 (0.12)	0.081
Log (time to close)	3.63 (0.02)	3.66 (0.03)	−0.03 (0.03)	0.276	3.63 (0.02)	3.67 (0.03)	−0.04 (0.02)	0.052	0.01 (0.03)	0.833
Log (time to open)	5.29 (0.12)	5.13 (0.14)	0.16 (0.08)	0.037	5.07 (0.11)	4.97 (0.12)	0.11 (0.05)	0.044	0.05 (0.09)	0.562
Log (time under 20)	4.24 (0.13)	4.19 (0.15)	0.05 (0.09)	0.573	4.15 (0.12)	4.07 (0.13)	0.08 (0.06)	0.166	−0.03 (0.10)	0.757
Log (number oscillations)	9.86 (1.20)	8.97 (0.97)	2.54 (0.71)	<0.001	8.80 (1.09)	9.85 (1.16)	−1.05 (0.48)	0.029	3.59 (0.86)	<0.001
log (total blink time)	5.50 (0.10)	5.37 (0.12)	0.13 (0.06)	0.042	5.31 (0.09)	5.23 (0.10)	0.08 (0.04)	0.087	0.06 (0.08)	0.482

Notes: p-values 1–3 correspond to (1) the difference between blink parameters at baseline and during activity for Control athletes, (2) the difference between blink parameters at baseline and post-head impact for Head Impact athletes, and (3) the difference between Head Impact athletes versus Active Control athletes. Negative values indicate an increase in magnitude from baseline. There were also no statistically significant differences in the blink parameters at baseline between Control and Head Impact athletes for all parameters (p-values not shown).