The Integration of the Corneal and Limbal Fibrils in the Human Eye

Abstract

The precise orientation of the collagen fibrils in human cornea and sclera and the method by which these two areas fuse together at the limbus have never been determined, despite the importance of this information. From a consideration of the mechanics of the system, fibril orientation in the tissue has the potential to affect the curvature of the cornea so, by inference, refractive problems such as astigmatism involving an incorrect curvature of the cornea may be related to fibril orientation. The high intensity and small beam size of a synchrotron x-ray source has enabled us to study fibril orientation in post-mortem human cornea and sclera. Previously we have revealed two preferred directions of orientation in the cornea (Meek, K. M., T. Blamires, G. F. Elliot, T. Y. Gyi, and C. J. Nave. 1987. Curr. Eye Res. 6:841-846) and a circumcorneal annulus in the limbus (Newton, R. H., and K. M. Meek. 1998. Invest. Ophthalmol. & Visual Sci. 39: 1125-1134). Here we present the results of our investigation into the relationship between these two features. Our measurements indicate that the corneal fibrils oriented in the two preferred directions bend at the limbus to run circumferentially. On the basis of these results we propose a model as to how the human cornea and sclera fuse together.

Scleral birefringence as measured by polarization-sensitive optical coherence tomography and ocular biometric parameters of human eyes in vivo

“…7, SHG microscopy showed that the collagen fiber of sclera was parallel to the limbus. This is consistent with previous reports about the scleral structure [46,51,52]. In contrast, the collagen fiber of the posterior sclera shown in Fig.…”

Estimation of Jones matrix, birefringence and entropy using Cloude-Pottier decomposition in polarization-sensitive optical coherence tomography

“…6(e) and 6(g), which showed high entropy but low local retardation. Since this region corresponds to the corneoscleral limbus, where the corneal and scleral laminar tissues change transitionally with fibrovascular ridges [60,61], the anisotropic fibrous structure might have anisotropic optic axes in the kernel window and have resulted in the high entropy. It is known that such anisotropic fibrous structure can be found at various biological tissues [62][63][64].…”

A computational remodeling approach to predict the physiological architecture of the collagen fibril network in corneo-scleral shells

“…The concentration of the collagen fibril orientations towards the circumferential direction at the limbus predicted by the remodeling algorithm can be interpreted as the development of a fibrillar annulus. From synchrotron X-ray diffraction data, the existence of a circumcorneal annulus of collagen fibrils at the limbus is well known (Newton and Meek 1998). The density of corneal fibril orientations of both families ρ fam1 (ϕ) + ρ fam2 (ϕ) predicted by the remodeling algorithm at the biological equilibrium (t/t * = 20) is compared in Fig.…”

“…In particular, Meek et al (1989) reported, using X-ray fibril diffraction, that the network of collagen fibrils in the central region of human corneas is characterized by two preferred directions, superior-inferior and nasal-temporal. Toward the limbus, there was only one preferred direction tangential to the limbus, where a circumcorneal annulus of collagen fibrils has been observed (Newton and Meek 1998;Aghamohammadzadeh et al 2004).…”