Evaluation of volumetric and diffusional brain changes and their associations with retinal structures and visual field function in glaucoma using MRI, OCT and perimetry

Abstract

Purpose : To evaluate the extent of anatomical changes of the retinal ganglion cell axons and trans-neuronal changes in the optic radiation across glaucoma stages using non-invasive MRI and clinical ophthalmic assessments.

Methods : This observational, cross-sectional study included 21 advanced glaucoma, 16 early glaucoma, and 13 healthy subjects who underwent spectral-domain OCT imaging of the eye, 3-Tesla anatomical MRI, diffusion tensor imaging (DTI) of the brain, and perimetry. Glaucoma staging criteria were based on recommendation by the American Glaucoma Society ICD-10 coding guidelines. Optic nerve and optic chiasm volumes were manually estimated from anatomical MR images. DTI-derived parametric values [fractional anisotropy (FA), mean diffusivity (DTI-MD), axial diffusivity (AD), and radial diffusivity (RD)] were extracted using manual regions-of-interests drawn on the optic radiation of each hemisphere. The anatomical MRI and DTI parameters were compared to clinical OCT parameters [peripapillary retinal-nerve-fiber-layer (pRNFL) thickness, macular ganglion-cell-inner-plexiform layer (GCIPL) thickness, optic nerve head cup-to-disc ratio (C/D)], visual field mean deviation (VF-MD), and to each other using linear mixed-effects models. Each parameter was also compared across groups using one-way MANOVA and receiver operating characteristic (ROC) analyses.

Results : From linear mixed effects models, optic nerve and optic chiasm volumes were associated positively with pRNFL thickness and VF-MD (p<0.05), but not GCIPL thickness or C/D. Optic chiasm volume was significantly associated with FA, DTI-MD, and RD, while optic nerve volume was negatively associated only with RD (p<0.05). Summary statistics in Figure 1 indicated significantly thinner pRNFL and higher C/D in early glaucoma than healthy control, whereas volumetric brain measurements, optic radiation DTI parameters (FA and RD), and VF-MD altered significantly between early and advanced glaucoma. ROC analyses in Figure 2 indicated differential abilities among MRI and clinical ophthalmic techniques to distinguish between glaucoma stages.

Conclusions : Both volumetric and diffusional brain changes measured from anatomical MRI and DTI may be useful for examining glaucomatous damages along the visual pathway complementary to OCT and perimetry.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.