Number of mTBIs is Associated with Increased Myopia in Post-9/11 Veterans

Abstract

Purpose : To investigate the association between the number of mild traumatic brain injuries (mTBI) during military service and distance acuity in Post-9/11 Veterans.

Methods : Participants were recruited from the Translational Research Center for TBI and Stress Disorders (TRACTS) longitudinal cohort study. The core battery for this ongoing study of Post-9/11 Veterans includes biologic/medical and genetic screening, structural and functional neuroimaging, as well as cognitive and psychological assessments. Screening assessments include the Boston Assessment of Traumatic Brain Injury – Lifetime (BAT-L), a semi-structured interview used to assess history of TBIs prior to, during, and after military service. Military TBIs include TBIs acquired during military service through blast exposure or any other mechanisms (e.g. blunt force trauma). A clinical exam was completed in addition to the core TRACTS battery in a random subset of participants between August 2015 and April 2017 at their repeat evaluation. The exam included measuring near and distance acuity, refractive error, ocular alignment, convergence, accommodation, and eye movements (fixation, pursuit, and saccades).

Results : Sixty-three eyes of thirty-two Post-9/11 veterans were included in analyses (90% male; mean age = 36.97±10.18). Multiple linear regression analyses completed with age and pinhole acuity as covariates show that the number of military mTBIs was associated with deficits in distance acuity (β=0.353, t=3.332, p=0.001). Including only the subset of participants with a positive history of military mTBIs, we find that this relationship remains when the years since last TBI is included as a covariate in the regression model. Additional analyses showed that the number of military mTBIs was not associated with deficits in near acuity thresholds (p=0.261).

Conclusions : The current results show that increasing numbers of military mTBIs is associated with decreasing visual acuity function in this sample of Post-9/11 Veterans. This relationship cannot be accounted for by the age of participants or the time since the last mTBI, and does not generalize to near acuity. This result is consistent with post-traumatic pseudomyopia that has been previously reported in other closed-head injury studies, though additional work is ongoing to further delineate the underlying mechanism leading to the observed changes in distance acuity functioning.

This is a 2020 ARVO Annual Meeting abstract.