Differences In Fixational Eye Movements Following Concussion: The Role Of The Fixation Task

There is a clinical need for rapid, objective tools for the identification of ocular impairment following concussion. Research has demonstrated that the amplitude of fixational eye movements (FEMS), small motions of the eye that occur during brief (10s) fixation, is larger following concussion. Although these findings highlight the potential utility of FEMS to rapidly identify concussion, what remains unclear is which FEMS fixation task is most effective for identifying concussion. PURPOSE: Evaluate the utility of different FEMS fixation tasks in identifying concussion from controls. METHODS: FEMS were measured using a tracking scanning laser ophthalmoscope in patients with concussion (N = 20; CONCUSS) and matched (age, sex) orthopedic injury controls (N = 16; OI-CONTROLS) (<7 days from injury). Participants fixated on the center of an imaging raster in the presence and absence of a target for 10s. Independent samples t-tests were used to compare saccade amplitude and bivariate contour ellipse area (BCEA), a metric that quantifies the spatial extent of fixation, across CONCUSS and OI-CONTROLS. RESULTS: Fixational saccade amplitude (deg) was significantly larger in CONCUSS (M = 0.47, SEM = 0.05) than OI-CONTROLS (M = 0.30, SEM = 0.05) in the absence of a central target stimulus (p = 0.02; Fig 1a), whereas no significant difference was supported when participants fixated on the central target stimulus (p > 0.05). BCEA (deg2) was also significantly larger in CONCUSS (M = 0.78, SEM = 0.19) compared to OI-CONTROLS (M = 0.22, SEM = 0.07; p = 0.021; Fig 1b), but again, only in the absence of the central target stimulus. CONCLUSIONS: These findings extend previous research on FEMS following concussion by highlighting the importance of measuring FEMS without a fixation target. Results suggest that precise fixation is particularly challenging following concussion when no target is present, which may be due to deficits in attention associated with this injury. Supported by: R44NS095090 "Retinal eye-tracking as a prognostic tool for traumatic brain injury and concussion"