Indirect Traumatic Optic Neuropathy in Mild Chronic Traumatic Brain Injury

Purpose: To analyze the clinical presentation and optical coherence tomography (OCT) findings in indirect traumatic optic neuropathy (ITON) in veterans with chronic mild traumatic brain injury (mTBI). Methods: This retrospective study is the first to describe the OCT pattern of subclinical to mild ITON in veterans with chronic mTBI. The thicknesses of the macular ganglion cell layer (mGCL), peripapillary retinal nerve fiber layer (pRNFL), and subfoveal choroidal layer were analyzed in young veterans who had mTBI of >6 months' duration and either blunt head injury or improvised explosive device (IED) concussions. Results: Three major OCT findings were demonstrated: (1) temporal pRNFL thinning was associated with subclinical TON in the eyes of chronic mTBI patients compared with controls; within mTBI subjects, nasal mGCL thinning at the 3-mm modified Early Treatment Diabetic Retinopathy Study circle diameter distance from the fovea correlated with the corresponding temporal retinal nerve fiber layer thinning; (2) inner (1 mm) superior thinning was greater than that of the temporal mGCL in blunt head injury and could potentially distinguish it from IED concussive head trauma; and (3) subfoveal choroidal thinning was significantly worse in eyes of mTBI patients compared with those of controls. Conclusions: These OCT findings may contribute to the understanding of the spectrum of visual injuries resulting from head trauma.