Centre for Ophthalmology and Visual Science and the ARC Centre of Excellence in Vision Science, The University of Western Australia, 2 Verdun Street, Nedlands, 6009 Perth, Australia.
Exp Eye Res. 2009 Nov;89(5):618-28. doi: 10.1016/j.exer.2009.06.002. Epub 2009 Jun 11.
Intraocular pressure and cerebrospinal fluid (CSF) pressure are important determinants of the trans-laminar pressure gradient which is believed to be important in the pathogenesis of glaucomatous optic nerve degeneration. Computational models and finite element calculations of optic nerve head biomechanics have been previously used to predict pressures and stresses in the human optic nerve. The purpose of this report is to morphometrically compare the optic nerve laminar and pia mater structure between humans and dogs, and to use previously reported tissue pressure measurements in the dog optic nerve to estimate individual-specific human optic nerve pressures and pressure gradients. High resolution light microscopy was used to acquire quantitative histological measurements from sagittal sections taken from the middle of the optic nerve in 34 human cadaveric eyes and 10 dog eyes. Parameters measured included the pre-laminar and lamina cribrosa thickness, distance from posterior boundary of lamina cribrosa to inner limiting membrane (ILM), shortest distance between anterior lamina cribrosa surface and subarachnoid space, shortest distance between ILM and inner surface of pia mater in contact with the subarachnoid space and optic nerve diameter. Pia mater thickness in the proximal 4 mm of post-laminar nerve was also determined. There was no significant difference in lamina cribrosa thickness between dog and human eyes (P = 0.356). The distance between the intraocular and subarachnoid space was greater in dogs (P < 0.001). Pia mater thickness was greatest at the termination of subarachnoid space in both species. In humans, pia mater thickness decreased over the proximal 500 mum to reach a constant value of approximately 60 mum. In dogs this decrease occurred over 1000 mum to reach a constant diameter of approximately 30 mum. Using previous measurements of optic nerve pressures and pressure gradients in dogs we estimate that at an IOP of 15 mmHg and a CSF pressure of 0 mmHg the mean pressure difference across the human pia mater will be 4.8 +/- 2.2 mmHg. If we assume that the pressure difference between the intraocular space and post-laminar tissue falls across the entire thickness of the human lamina cribrosa then an estimate of the trans-laminar pressure gradient is 2.0 +/- 0.8 mmHg/100 mum. If we assume that this pressure difference only occurs across the dense collagenous plates of the posterior lamina cribrosa then a trans-laminar pressure gradient high estimate of 3.3 +/- 1.4 mmHg/100 mum is calculated. Changes in tissue pressure gradients in the optic nerve may be an important factor in the pathogenesis of glaucomatous optic neuropathy.
眼内压和脑脊液（CSF）压力是跨层压力梯度的重要决定因素，据信跨层压力梯度在青光眼视神经变性的发病机制中很重要。先前已经使用视神经头生物力学的计算模型和有限元计算来预测人视神经中的压力和应力。本报告的目的是对人眼和狗眼的视神经层状和软脑膜结构进行形态计量比较，并使用先前在狗视神经中报告的组织压力测量值来估计个体特异性人视神经压力和压力梯度。高分辨率光显微镜用于从视神经中部的矢状切片中获取来自 34 个人尸体眼睛和 10 只狗眼睛的定量组织学测量值。测量的参数包括前层状和筛板厚度、筛板后边界到内界膜（ILM）的距离、前筛板表面和蛛网膜下腔之间的最短距离、ILM 和与蛛网膜下腔接触的软脑膜内表面之间的最短距离以及视神经直径。还确定了后层状神经近端 4 毫米内的软脑膜厚度。狗眼和人眼的筛板厚度没有显着差异（P = 0.356）。狗眼的眼内空间和蛛网膜下腔之间的距离更大（P <0.001）。在两种物种中，软脑膜厚度在蛛网膜下腔终止处最大。在人类中，软脑膜厚度在近端 500 微米处减少，达到约 60 微米的恒定值。在狗中，这种减少发生在 1000 微米处，达到约 30 微米的恒定直径。使用先前在狗中测量的视神经压力和压力梯度，我们估计在 IOP 为 15 mmHg 和 CSF 压力为 0 mmHg 的情况下，穿过人软脑膜的平均压力差将为 4.8 +/- 2.2 mmHg。如果我们假设眼内空间和后层状组织之间的压力差跨越人筛板的整个厚度，则跨层压力梯度的估计值为 2.0 +/- 0.8 mmHg/100 µm。如果我们假设仅在筛板后部的密集胶原板上发生这种压力差，则计算出的跨层压力梯度高估计值为 3.3 +/- 1.4 mmHg/100 µm。视神经中组织压力梯度的变化可能是青光眼视神经病变发病机制中的一个重要因素。
