Retinal manifestations of traumatic brain injury.

Retinal nerve fibre layer (RNFL) and ganglion cell layer (GCL) thinning occur weeks to months after traumatic brain injury (TBI), even without computed tomography (CT) findings. The patterns of RNFL and GCL loss and their relationship to TBI severity and CT findings have not been characterised. This observational study included consecutive patients assessed in hospital after TBI. All patients underwent OCT. A literature review was conducted to determine the test-retest variability of RNFL and GCL measurements. Of 135 included patients, 62 had follow up OCTs. The test-retest limit of agreement for global RNFL thickness was 4 µm. Two patients had symptomatic traumatic optic neuropathy, 17 had less severe RNFL thinning on follow up, six RNFL thickening and 31 no RNFL changes. Higher TBI severity, Marshall CT classification and lower time to first OCT after injury strongly associated with subsequent RNFL changes (p < 0.001 for all). Global RNFL thickness in patients with initial OCT < 42 days after injury declined by 1.74 µm/month with Marshall II CT findings, compared 0.05 µm/month with Marshall I, and 3.69 µm/month after severe TBI, versus 1.47 µm/month after mild. Subclinical OCT changes therefore occur after TBI, and may contribute to future multimodal TBI diagnostic and severity assessments.