Newton R H, Meek K M
The Open University, The Oxford Research Unit, United Kingdom.
Invest Ophthalmol Vis Sci. 1998 Jun;39(7):1125-34.
To quantify the orientation of the collagen fibrils in the human limbus and to compare it with the orientation in the cornea and the sclera.
Fibril orientation was measured from 100 synchrotron x-ray diffraction patterns collected at intervals along lines across the cornea, limbus, and sclera.
A distinct circumcorneal annulus of collagen fibrils was revealed in the limbus. For the individual cornea investigated, the annulus was not uniform around the corneal circumference; its width, fibril angular spread, and fibril density all varied with position. The average width of the annulus was narrower in the superior sector (1.5 mm) than in the inferior sector (2.0 mm). The results from the edge of the cornea suggested that the preferentially aligned corneal fibrils bend sharply at the limbus to run circumferentially or that, together with this bending or alone, extra fibrils arising in the sclera run across this zone. In the cornea the biaxial preferred directions became more pronounced from the center of the cornea toward the limbus along the superior-inferior axis.
The excess of circumferential fibrils in the limbus, predicted from the sharp change of curvature in the surface of the eye at the limbus, appeared to take the form of a well-defined annulus. From a consideration of the mechanics of the system it seemed probable that the purpose of this annulus was to help maintain the correct curvature of the cornea. Before further research, it was hypothesized that some refractive problems associated with an incorrect curvature of the cornea may be related in part to abnormalities of this circumcorneal annulus.
量化人角膜缘胶原纤维的取向，并将其与角膜和巩膜中的取向进行比较。
从沿角膜、角膜缘和巩膜的线间隔采集的100张同步加速器X射线衍射图测量纤维取向。
在角膜缘发现了一个明显的角膜周围胶原纤维环。对于所研究的个体角膜，该环在角膜圆周周围并不均匀；其宽度、纤维角展度和纤维密度均随位置而变化。该环的平均宽度在上半部分（1.5毫米）比在下半部分（2.0毫米）更窄。角膜边缘的结果表明，优先排列的角膜纤维在角膜缘处急剧弯曲以沿圆周方向排列，或者与这种弯曲一起或单独地，巩膜中产生的额外纤维穿过该区域。在角膜中，双轴优先方向从角膜中心沿上下轴朝向角膜缘变得更加明显。
从角膜缘处眼球表面曲率的急剧变化预测，角膜缘处圆周纤维的过量似乎采取了明确界定的环的形式。从系统力学的角度考虑，这个环的目的似乎是帮助维持角膜的正确曲率。在进一步研究之前，有人假设一些与角膜曲率不正确相关的屈光问题可能部分与这个角膜周围环的异常有关。
