Abstract
This study intended to examine effects of repetitive sub-concussive head impacts on
ocular near point of convergence (NPC). 20 healthy young adult soccer players were
assigned to either a heading or control group. Heading subjects completed 10 headers
of soccer balls projected at a speed of 11.2 m/s. Control subjects did not perform
heading. Linear head acceleration was measured with a triaxial accelerometer. The
NPC assessment was performed at pre-, 0 h post-, and 24 h post-heading. During the
NPC assessment participants were seated and a visual target was moved towards the
eyes at 1cm/sec. The participant signaled when he/she experienced diplopia or deviation
of the eye was observed, and the distance was recorded. The assessment was repeated
twice and average NPC scores were used for further analysis. Soccer heading induced
mean group head accelerations of 14.49±5.4 g. Mild head impacts led to an increased NPC distance, which was supported by a significant
Group x Time interaction. In the heading group, 0 h post- and 24 h post-heading NPC
scores were significantly receded compared to baseline. Conversely, NPC scores for
the control group showed no difference over time. Our findings indicate that mild
frontal head impacts affekt NPC for a minimum of 24 h-post heading, suggesting that
oculomotor processes are disrupted, at least transiently, by repetitive mild head
impact.
Key words
convergence insufficiency - head impact kinematics - sports concussion - eye
