Quantitative evaluation of intraorbital optic nerve in optic atrophy using diffusion tensor imaging

Abstract

The aim of this study is to quantitatively investigate the microstructural properties of the optic nerve (ON) in vivo using diffusion tensor imaging (DTI) in patients with unilateral optic atrophy (OA) and to determine their association with retinal nerve fiber layer (RNFL) thickness of the optic nerve head (ONH). Six patients with unilateral OA and 11 control subjects underwent DTI. ONs from ONH to the orbital apex were tracked. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were computed in both ONs and their correlation with RNFL thickness measured using optical coherence tomography was also analyzed. FA of atrophic ON was lower than that of non-affected and control ONs (atrophic [A], 0.136 ± 0.059; non-affected [N], 0.384 ± 0.048; control [C], 0.389 ± 0.053). MD and RD of atrophic ONs were higher than those of non-affected and control ONs (MD, A, 0.988 ± 0.247; N, 0.658 ± 0.058; C, 0.687 ± 0.079; RD, A, 0.920 ± 0.247; N, 0.510 ± 0.054; C, 0.532 ± 0.078). All DTI measures of atrophic ON except for AD showed a significant correlation with RNFL thickness of ONH; FA showed the strongest correlation, followed by RD and MD (FA, R2 = 0.936, P < 0.001; RD, R2 = 0.795, P < 0.001; MD, R2 = 0.655, P = 0.001). This study reports quantitative analysis of the ON using DTI and differences in DTI measures between atrophic and normal ONs. The significant correlation between DTI measures and RNFL thickness suggests the applicability of DTI as a clinical tool to evaluate the ON.

Thyroid-associated ophthalmopathy: Using diffusion tensor imaging to evaluate visual pathway microstructural changes

“…A variety of radiologic metrics has been utilized to assist in the diagnosis of optic nerve alterations, such as detection of apical crowding on scanning, decreased diameter of the optic nerve on T1-weighted imaging, ADC value to measure the optic nerve, and T2 mapping to detect intraorbital optic nerve changes (25, 26), study on the posterior visual pathway still remains few. Diffusion tensor imaging is a noninvasive functional magnetic resonance technique (27,28). It can examine white matter structure in vivo since the brain's white matter tracts are made up of bundles of axons that are often arranged in a variety of orientations.…”

“…Diffusion tensor imaging is a noninvasive functional magnetic resonance technique ( 27 , 28 ). It can examine white matter structure in vivo since the brain's white matter tracts are made up of bundles of axons that are often arranged in a variety of orientations.…”

“…Extensive damage caused by myelin and axon loss reduces anisotropy. This leads to increased diffusion perpendicular to the white matter tract, enhanced overall diffusivity (MD), and decreased tissue directionality (FA) ( 27 ). Neuronal and axonal degeneration following injury to cells with which they synapse is called trans-synaptic degeneration ( 32 ).…”

Tractometry of Human Visual White Matter Pathways in Health and Disease

“…In addition, Haykal and colleagues (2020) 109 demonstrated that dMRI data acquired from glaucoma patients exhibited abnormalities, such as reduced FA, in the optic nerve. Hong and colleagues (2022) 110 used a similar tractometry approach on dMRI data acquired from patients with optic atrophy and demonstrated that diffusivity measurements, such as FA, were significantly different from atrophic and non-affected ONs. Moon and colleagues (2021) 111 used the same approach to test cognitively normal elderly populations and demonstrated a correlation between ON tractometry measurements and participants’ age.…”