Quantitative assessment of the visual pathway by DTI‐MRI in Glaucoma

Purpose In glaucomatous optic nerve atrophy (glOA) damage of retinal ganglion cells may continue to the linked optic radiations (OR). This study investigated differences between glOA and non-glOA in relation to impairment of the optic radiations using DTI-MRI. Methods We examined 42 patients with healthy optic nerve head and no ophthalmological signs of an affected visual pathway, 134 glOA patients, and 35 non-glOA patients (mean age 54±15.9 years, 64±12.4 years, and 49±15.2 years, respectively). The participants underwent the diffusion tensor imaging (DTI) to measure the axonal integrity, i.e. fractional anisotropy (FA) and mean diffusivity (MD), and demyelination, i.e. radial diffusivity (RD), in the semi-automatically outlined optic radiations. The results were correlated with the retinal nerve fiber layer thickness (RNFL) acquired by the Spectralis optical coherence tomography and with the mean defect provided by standard automatic perimetry. Results Age correlated significantly with the DTI parameters in all groups. If corrected for age only in the glOA patient group the mean defect correlated with FA (r=-0.31; p=0.004) and RD (r=0.22; p=0.043). In the non-glOA group the RNFL correlated with MD (r=-0.57; p=0.027) and RD (r=-0.59; p=0.019). The control group did not show a correlation of DTI parameters with the mean defect or RNFL. Conclusion In both types of optic nerve atrophy a correlation was found between visual field and axonal integrity/ demyelination of the optic radiations, and the reduction of the RNFL was associated with an impairment of the axonal integrity/ demyelination of the optic radiation. The damage of the optic nerve was significantly associated with loss of RNFL and ageing.