Optic Radiations Microstructural Changes in Glaucoma and Association with Severity: A Study Using 3Tesla-Magnetic Resonance Diffusion Tensor Imaging

Purpose:To compare microstructural changes along the optical radiations and brain structure volumes between glaucoma and control subjects using in vivo magnetic resonance imaging and to analyze their association with severity of the disease.Methods:A total of 50 open-angle glaucoma subjects and 50 healthy age- and sex-matched controls underwent detailed ophthalmologic examinations (including visual field testing [VF], funduscopy, and spectral-domain optical coherence tomography) as well as diffusion tensor imaging (DTI) using 3.0-Tesla magnetic resonance imaging. Fractional anisotropy (FA), mean diffusivity, radial diffusivity (RD), and axial diffusivity (AD) were quantified semiautomatically along the optical radiations. DTI parameters and volumes of specific brain structures were compared between cases and controls using conditional logistic regression. Association between DTI metrics and the severity of the disease was studied using linear mixed regression analyses.Results:In glaucoma subjects, optic radiations FA was significantly lower (0.57 vs. 0.59; P = 0.02) and RD was significantly higher (52.78 10-5 mm2/s vs. 49.74 10-5 mm2/s; P = 0.03) than in controls. Optic radiations FA was significantly correlated with homolateral functional and structural damage of glaucoma (mean deviation of VF [P = 0.03], retinal nerve fiber layer thickness [P = 0.03], vertical cup to disc ratio [P = 0.0007]). Volume and DTI parameters of other brain structures (including hippocampus) were not significantly different between glaucoma patients and controls.Conclusions:We evidenced microstructural modifications along visual pathways of glaucoma patients and these alterations were correlated with disease severity. The association of glaucoma with other neurodegenerative alterations would need further exploration and a prospective follow-up of our cohort of subjects. (ClinicalTrials.gov number, NCT01621841).