Boote Craig, Dennis Sally, Huang Yifei, Quantock Andrew J, Meek Keith M
Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Wales, UK.
J Struct Biol. 2005 Jan;149(1):1-6. doi: 10.1016/j.jsb.2004.08.009.
We have applied wide-angle X-ray scattering to the human cornea in order to quantify the relative number of stromal collagen fibrils directed along the two preferred corneal lamellar directions: superior-inferior and nasal-temporal. The data suggest that, on average, the two directions are populated in equal proportion at the corneal centre. Here, approximately one-third of the fibrils throughout the stromal depth tend to lie within a 45 degrees sector of the superior-inferior meridian, and similarly for the nasal-temporal direction. However, in some eyes we have measured significant differences between the two preferential fibril populations, with some corneas exhibiting as much as 25% more collagen in one direction than the other. Based on these findings, a mechanical model of the normal cornea may be envisaged, whereby the fibril tension in the underlying "background" of isotropically arranged collagen helps to balance the intraocular pressure; while the extra preferentially aligned fibrils take up the additional tensile stress along the superior-inferior and nasal-temporal meridians exerted by the rectus muscles and the orbicularis. It is possible that, through a direct impact on the elastic modulus of the tissue, an imbalance of superior-inferior and nasal-temporal fibrils in some eyes might affect corneal shape.
我们已将广角X射线散射应用于人类角膜，以量化沿角膜两个主要板层方向排列的基质胶原纤维的相对数量：上下方向和鼻颞方向。数据表明，平均而言，在角膜中心这两个方向的纤维数量相等。在此，贯穿基质深度约三分之一的纤维倾向于位于上下子午线45度扇形范围内，鼻颞方向情况类似。然而，在一些眼睛中，我们测量到这两个优先排列的纤维群体之间存在显著差异，一些角膜在一个方向上的胶原含量比另一个方向多25%。基于这些发现，可以设想一个正常角膜的力学模型，即各向同性排列的胶原纤维的潜在“背景”中的纤维张力有助于平衡眼内压；而额外优先排列的纤维则承受由直肌和眼轮匝肌沿上下和鼻颞子午线施加的额外拉应力。在某些眼睛中，上下和鼻颞纤维的失衡可能通过直接影响组织的弹性模量，进而影响角膜形状。
