For U.S. college football players, head impacts that don’t cause concussion symptoms do still cause subtle and lingering changes in the eyes’ ability to focus, according to a new study reported in JAMA Ophthalmology. The results might provide a new tool for measuring the severity of the “sub-concussive” brain impacts that athletes and others, like soldiers, experience regularly, researchers say. Researchers studied 29 football players who volunteered to wear special mouthguards containing electronics that measured the number and magnitude of head impacts for each player. The players also had eye exams before each practice began and after the season was over.
There was no difference in the types or frequency of physical symptoms reported by players in either group. But researchers found that players in the high-impact group had gradual increases throughout the season in the “near point of convergence” of their eyes, which is the closest point at which the two eyes can view something clearly before double-vision occurs. The changes plateaued after a while, and then resolved by three weeks postseason.