The collagen fiber architecture of the peripapillary sclera (PPS), which surrounds the scleral canal, is a critical factor in determining the mechanical response of the optic nerve head (ONH) to variations in intraocular pressure (IOP). Experimental and clinical evidence point to IOP-induced deformations within the scleral canal as important contributing factors of glaucomatous neural tissue damage and consequent vision loss. Hence, it is imperative to understand PPS architecture and biomechanics. Current consensus is that the fibers of the PPS form a closed ring around the canal to support the delicate neural tissues within. We propose an alternative fiber architecture for the PPS, in which the scleral canal is supported primarily by long-running fibers oriented tangentially to the canal. We present evidence that this tangential model is consistent with histological observations in multiple species, and with quantitative measurements of fiber orientation obtained from small angle light scattering and wide-angle X-ray scattering. Using finite element models, we investigated the biomechanical implications of a tangential fiber PPS architecture. We found that the tangential arrangement of fibers afforded better mechanical support to the tissues within the scleral canal as compared to a simple circumferential ring of fibers or a combination of fibers oriented radially and circumferentially. We also found that subtle variations from a tangential orientation could reproduce clinically observed ONH behavior which has yet to be explained using current theories of PPS architecture and simulation, namely, the contraction of the scleral canal under elevated IOP.

Statement of Significance

It is hypothesized that vision loss in glaucoma is due to excessive mechanical deformation within the neural tissue inside the scleral canal. This study proposes a new model for how the collagen of the peripapillary sclera surrounding the canal is organized to support the delicate neural tissue inside. Previous low-resolution studies of the peripapillary sclera suggested that the collagen fibers are arranged in a ring around the canal. Instead, we provide microscopic evidence suggesting that the canal is also supported by long-running interwoven fibers oriented tangentially to the canal. We demonstrate that this arrangement has multiple biomechanical advantages over a circular collagen arrangement and can explain previously unexplained experimental findings including contraction of the scleral canal under elevated intraocular pressure.

中文翻译：

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再次探讨乳突周围巩膜结构：切向纤维模型及其生物力学意义

围绕巩膜管的乳头周围巩膜（PPS）的胶原纤维结构是决定视神经头（ONH）对眼内压（IOP）变化的机械反应的关键因素。实验和临床证据表明，眼压引起的巩膜管内变形是青光眼神经组织损伤和随之而来的视力丧失的重要因素。因此，必须了解PPS架构和生物力学。目前的共识是，PPS的纤维在管周围形成一个封闭的环，以支撑其中的脆弱神经组织。我们提出了一种用于PPS的替代纤维结构，其中巩膜管主要由切向于该管的长距离运行纤维支撑。我们提供的证据表明，该切向模型与多种物种的组织学观察结果一致，并与从小角度光散射和广角X射线散射获得的纤维取向的定量测量结果一致。使用有限元模型，我们研究了切向光纤PPS体系结构的生物力学含义。我们发现，与简单的纤维周向环或径向和周向定向的纤维组合相比，纤维的切向排列为巩膜管内的组织提供了更好的机械支撑。我们还发现，切向方向的细微变化可以重现临床观察到的ONH行为，这尚未使用当前的PPS体系结构和模拟理论进行解释，即

重要声明

据推测，青光眼的视力丧失是由于巩膜管内神经组织内过度的机械变形所致。这项研究提出了一种新的模型，用于围绕运河的乳头周围巩膜的胶原蛋白如何组织以支持内部的脆弱神经组织。先前对乳头周围巩膜的低分辨率研究表明，胶原纤维排列在管周围的环中。取而代之的是，我们提供了微观证据，表明该运河也受到与该运河相切定向的长距离交织纤维的支撑。我们证明这种安排比圆形胶原安排有多个生物力学优势，并可以解释以前无法解释的实验结果，包括在眼压升高时巩膜管的收缩。