Laboratory for Experimental Ophthalmology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.
Department of Ophthalmology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.
Eur J Radiol. 2020 Dec;133:109356. doi: 10.1016/j.ejrad.2020.109356. Epub 2020 Oct 16.
To characterize neurodegeneration of glaucomatous optic nerves (ONs) in terms of changes in axonal density and morphology using fixel-based analysis (FBA), a novel framework for analyzing diffusion-weighted MRI (DWI). Furthermore, we aimed to explore the potential of FBA measures as biomarkers of glaucomatous ON degeneration.
DWI scans were obtained from 15 glaucoma patients and 15 controls. ONs were tracked and segmented into their three anatomical segments; intraorbital (IO), intracanalicular (ICAN) and intracranial (ICRAN). For each segment, FBA measures were computed, which included fiber density (FD; a measure of axonal density), fiber-bundle cross-section (FC; an estimate of morphological changes), and fiber density and cross-section (FDC). Peripapillary retinal nerve fiber layer (pRNFL) thickness and visual field mean deviation (VFMD) were assessed for glaucoma patients. ANCOVA was used to compare FBA values between the two groups, and Spearman's correlation analysis was used to test the correlation between FBA measures and pRNFL thickness and VFMD.
All glaucomatous ON segments showed a significant loss of FD and FDC compared to the controls, while a loss of FC was found in the IO and ICRAN segments only. FD and FDC values of the IO and ICAN segments of glaucomatous ONs showed significant correlations with pRNFL thickness and VFMD.
Glaucomatous ONs exhibit lower FD and FC compared to controls, indicating axonal loss and gross atrophy. The correlation between FBA measures of glaucomatous ONs and established clinical tests of glaucoma demonstrates the potential of FBA measures as biomarkers of glaucomatous ON degeneration.
使用基于固定效应分析（FBA）的方法，从轴突密度和形态变化的角度来描述青光眼视神经（ON）的神经退行性变，FBA 是一种分析扩散加权磁共振成像（DWI）的新框架。此外，我们旨在探讨 FBA 测量作为青光眼 ON 变性生物标志物的潜力。
从 15 名青光眼患者和 15 名对照者中获取 DWI 扫描。将 ON 追踪并分段为三个解剖段：眶内（IO）、管内（ICAN）和颅内（ICRAN）。对于每个节段，计算了 FBA 测量值，包括纤维密度（FD；轴突密度的度量）、纤维束横截面积（FC；形态变化的估计）和纤维密度与横截面积（FDC）。对青光眼患者进行视盘周围视网膜神经纤维层（pRNFL）厚度和视野平均偏差（VFMD）评估。采用协方差分析（ANCOVA）比较两组间 FBA 值，采用 Spearman 相关分析检验 FBA 测量值与 pRNFL 厚度和 VFMD 的相关性。
与对照组相比，所有青光眼 ON 段的 FD 和 FDC 值均显著降低，而仅在 IO 和 ICRAN 段发现 FC 降低。青光眼 ON 的 IO 和 ICAN 段的 FD 和 FDC 值与 pRNFL 厚度和 VFMD 呈显著相关。
与对照组相比，青光眼 ON 表现出较低的 FD 和 FC，表明存在轴突丢失和明显萎缩。青光眼 ON 的 FBA 测量值与青光眼的既定临床测试之间的相关性表明，FBA 测量值具有作为青光眼 ON 变性生物标志物的潜力。
