The optic nerve sheath (ONS) is biomechanically important. It is acted on by tension due to ocular movements, and by fluid shifts and/or alterations in intracranial pressure (ICP) in human disease, specifically in pathologies leading to intracranial hypertension. It has also been hypothesized that the ONS is acted on by altered ICP in astronauts exposed chronically to microgravity. However, a non-invasive method to quantify ONS biomechanical properties is not presently available; knowledge of such properties is desirable to allow characterization of the biomechanical forces exerted on the optic nerve head and other ocular structures due to the ONS. Thus, the primary objective of this study was to characterize the biomechanical properties (stiffness) of the human ONS in vivo as a necessary step towards investigating the role of ICP in various conditions, including Spaceflight Associated Neuro-ocular Syndrome (SANS). We acquired non-invasive magnetic resonance imaging (MRI) scans of ostensibly healthy subjects (n = 18, age = 30.4 ± 11.6 [mean ± SD] years) during supine and 15-degree head-down-tilt (HDT) postures, and extracted ONS contours from these scans. We then used finite element modeling to quantify ONS expansion due to postural changes and an inverse approach to estimate ONS stiffness. Using this non-invasive procedure, we estimated an in vivo ONS stiffness of 39.2 ± 21.9 kPa (mean ± SD), although a small subset of individuals had very stiff ONS that precluded accurate estimates of their stiffness values. ONS stiffness was not correlated with age and was higher in males than females.

视神经鞘 (ONS) 在生物力学上很重要。它是由眼球运动引起的张力，以及液体转移和/或人类疾病中颅内压 (ICP) 的改变，特别是在导致颅内高压的病理中起作用的。还假设长期暴露于微重力的宇航员的 ICP 改变了 ONS。然而，目前还没有量化 ONS 生物力学特性的非侵入性方法。需要了解这些特性，以便表征由于 ONS 作用在视神经乳头和其他眼部结构上的生物力学力。因此，本研究的主要目的是表征人 ONS在体内的生物力学特性（刚度）作为研究 ICP 在各种条件下的作用的必要步骤，包括航天相关神经眼综合征 (SANS)。我们在仰卧和 15 度头向下倾斜 (HDT) 姿势期间获得了表面上健康受试者（n = 18，年龄 = 30.4 ± 11.6 [平均值 ± SD] 岁）的非侵入性磁共振成像 (MRI) 扫描，以及从这些扫描中提取 ONS 轮廓。然后，我们使用有限元建模来量化由于姿势变化引起的 ONS 膨胀和估计 ONS 刚度的逆方法。使用这种非侵入性程序，我们估计了体内ONS 刚度为 39.2 ± 21.9 kPa（平均值 ± SD），尽管一小部分个体的 ONS 非常僵硬，无法准确估计其刚度值。ONS 硬度与年龄无关，男性高于女性。