Smooth Pursuit Gain Declines After A Single Season Of Football

Abstract

Repetitive head impacts (RHI), independent of concussion, can lead to alterations in brain activity and function, specifically within the midbrain, which can manifest as abnormal eye movements. PURPOSE: To evaluate the effect of repetitive head impacts on eye movements during a head stationary dynamic visual acuity (sDVA) task. METHODS: 11 NCAA Division I athletes [5 FB: all males; average age 21 years; 6 cross country (XC) athletes (3 females, 3 males; average age 20 years] participated in this study. Any athlete was excluded due to any existing non-corrected vision impairment, self-reported prior concussion history, and withdrawal from their sport due to injury or sickness. FB players had to sustain 20 impacts per week ≥10gs for inclusion. Student-athletes were assessed prior (PRE) to the start, in the middle (MID) and within 2-weeks of the conclusion of the season (POST) on an adaptive sDVA task. FB players wore instrumented mouthguards to track head impacts that were independently video verified. At each testing time point, participants completed 60 randomized trials of smooth pursuit (SPEM) (30°/s) and saccadic (90°/s) eye movements. Participants' eye movements were monitored (500Hz; Eyelink SR research, Ottawa, CN) while their heads were stabilized in a chin rest at a distance of 154cm from the 26° visual field monitor. Participants' task was to track the gap location (left, right, up, down) in a Landolt-C that moved across the screen (horizontally left to right). Using a 2-up-1-down staircase method the size of the stimulus and the gap varied based on the correct/incorrect responses during both smooth pursuit and saccadic trials. The primary measures were SPEM gain and saccadic mean velocity.