Brain injury from contact sports remains a hot topic among researchers, whether it’s high school and NFL football game tackles or cheerleading falls. Adding to the current literature, a new study has found that repeat soccer ball headings can also impair neuro-ophthalmic functions.

The investigation, published in JAMA Ophthalmology, found the brain’s neural circuitry that links cognitive and oculo-motor functions may be temporarily vulnerable to acute subconcussive head impacts after 10 soccer ball headings.

The randomized clinical trial used the King-Devick test (KDT) to evaluate neuro-ophthalmologic ability before, immediately following and two and 24 hours after soccer-ball headings. The researchers found 10 soccer-ball headings blunted the brain’s neuro-ophthalmologic ability to learn and adapt.

A total of 67 adult soccer players were randomized into either a heading group (n=36) or kicking (control) group (n=31). The heading group executed 10 headers with soccer balls projected at a speed of 25mph. The kicking-control group followed the same protocol but with 10 kicks.

Not surprisingly, the average peak linear head accelerations and peak rotational accelerations per impact for the heading group were higher—33.2g and 3.6krad/s², respectively—than the kicking group, which didn’t have any detectable head acceleration. Although both groups showed improvements in KDT speed, group differences occurred at all post-intervention points. The kicking-control group performed the test faster at zero hours (−2.2 seconds), two hours (−2.8 seconds), and 24 hours after the intervention (−2.0 seconds) compared with those in the heading group.

The study results indicate neuro-ophthalmologic function is affected—at least in the short-term—by subconcussive head impacts that may affect some individuals in certain contact sports, the researcher said. Further studies may help determine if these measures can be a useful clinical tool in detecting acute subconcussive injury, they added.