Diffusion tensor magnetic resonance imaging reveals visual pathway damage that correlates with clinical severity in glaucoma

Abstract

To investigate nerve fibre damage of the visual pathway in patients with primary open-angle glaucoma using tract-based spatial statistical analysis of diffusion tensor imaging and correlate these measures with the clinical severity of glaucoma. Cross-sectional study. Twenty-five individuals with primary open-angle glaucoma and 24 healthy controls were recruited. All subjects underwent detailed ophthalmological examinations, including the cup-to-disc ratio, retinal nerve fibre layer thickness and visual fields test. Diffusion tensor imaging of the visual pathway was performed using a 3.0-T magnetic resonance scanner. Diffusivity changes of the nerve fibres in the visual pathway were calculated through tract-based spatial statistical analysis. The mean diffusivity and fractional anisotropy were assessed and compared with ophthalmological measurements. Compared with controls, bilateral optic tracts and optic radiations in primary open-angle glaucoma patients showed significantly decreased fractional anisotropy and increased mean diffusivity (P < 0.05). In the glaucoma group, the fractional anisotropy of the optic tracts and optic radiations varied consistently with the cup-to-disc ratio, retinal nerve fibre layer thickness and visual function analysis, respectively (P < 0.05). The mean diffusivity of the optic tracts correlated with these ophthalmological measurements (P < 0.05). However, no significant correlation was observed between the mean diffusivity of the optic radiations and the ophthalmological measurements (P > 0.05). The optic tracts and optic radiations of primary open-angle glaucoma patients demonstrated radiological evidence of neurodegeneration. This varied with damage to the optic disc and with the loss of visual function. Tract-based spatial statistical analysis of diffusion tensor imaging is an objective and effective tool for detecting the loss of cortical nerve fibres in primary open-angle glaucoma.