Retinal Structural Changes Associated with Blast-Induced Mild Traumatic Brain Injury Identified on OCT Imaging

Abstract

Purpose : To assess retinal morphology differences in Post-9/11 Veterans with and without a history of blast-induced mild TBI (bmTBI) using optical coherence tomography (OCT) retinal segmentation.

Methods : Seventeen participants with a history of bmTBI (33 eyes; bmTBI+ group) and 11 participants without a history of mTBI (22 eyes; bmTBI- group) during military service participated (mean age: 37 ± 9.9; 89% male). Participants were recruited from the Translational Research Center for TBI and Stress Disorders (TRACTS) longitudinal cohort study of Post-9/11 Veterans. All TRACTS participants complete the Boston Assessment of Traumatic Brain Injury – Lifetime (BAT-L), a semi-structured interview assessing TBI history prior to, during, and after military service. Military mTBIs are further classified as due to blast or blunt force trauma. An ophthalmic clinical exam was completed in a subset of TRACTS participants returning for a repeat evaluation from 2015 and 2017. This included Heidelberg Spectralis OCT scans of the peripapillary and macular regions. Peripapillary scans were dedicated to the retinal nerve fiber layer (RNFL) thickness. Macular retinal layers were segmented and included RNFL, ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), and outer retinal layer thickness using an Early Treatment Diabetic Retinopathy Study (ETDRS) grid centered on the fovea (3 concentric rings at 1, 3, 6 mm).

Results : Linear mixed-effects models assessed differences across the bmTBI groups with grid location, eye, and age as fixed factors. The peripapillary RNFL was thinner in the bmTBI+ group (p = 0.002), and the difference was greater in the superior/nasal and inferior/nasal segments (p = 0.007). In the macular segmentation, the INL showed evidence of thinning in the bmTBI+ group (p = 0.014). In contrast, the ONL and outer retinal layer segment containing photoreceptors were found to be thicker in the bmTBI+ group (p < 0.001).

Conclusions : Blast mTBI was associated with thinning of inner retinal layers, in particular the peripapillary RNFL and macular INL. In contrast, outer retinal layers were found to be thicker. These results may support the chronic neuroinflammatory sequelae observed in recent animal models of low-level blast exposure on retinal morphology.

This is a 2021 ARVO Annual Meeting abstract.