Visual function and correlation with retinal structure in sports-related mild traumatic brain injury (mTBI)

AIMS: To investigate the effect of mild traumatic brain injury (mTBI) on retinal thickness as measured by optical coherence tomography (OCT), and on visual function as assessed by multifocal pupillary objective perimetry (mfPOP).METHODS: Thirty-seven male athletes with a history of acute concussion occurring 4 - 36 days previously (aged 21.6 ± 2.1 years, mean ± SD), eleven athletes with a history of head trauma 39 - 666 days previously (20.9 ± 2.0 years), and twelve athletes with no history of head trauma (22.5 ± 2.7 years) were compared to eighteen non-athlete controls (22.1 ± 1.9 years). Pupillary response amplitudes and delays were measured to 44 multifocal, dichoptic, regional stimulus presentations extending out to ±30° from the fovea. Full retinal thickness was measured with OCT in the nine zones of the Early Treatment Diabetic Retinopathy study (ETDRS) and this was correlated with the average pupillary response to stimulation in each zone. RESULTS: On average, athletes who suffered acute mTBI showed a significant reduction in response amplitude (-2.44 ± 0.48 dB, P < 0.0001). Response amplitudes of athletes with chronic mTBI were reduced relative to controls but this did not reach significance (-0.58 ± 0.48 dB, P =0.23). Local retinal thickness and pupillary response delays showed a significant negative correlation for all ETDRS retinal regions in athletes with acute mTBI (P < 0.05) but not in other groups.CONCLUSION: Response amplitudes were more informative than delay. A significant effect on pupillary response amplitudes were seen in the acute mTBI athletes whereas the chronic mTBI athletes demonstrated significant delay. A significant negative association between response delay and retinal thickness was found in acute mTBI. Pupillary response dynamics, particularly in conjunction with structural retinal changes, may be a potential biomarker of mild head trauma.