Abstract
It is thought that corneal surface topography may be stabilized by the angular orientation of out-of plane lamellae that insert into the anterior limiting membrane. In this study, micro-focus X-ray scattering data were used to obtain quantitative information about lamellar inclination (with respect to the corneal surface) and the X-ray scatter intensity throughout the depth of the cornea from the centre to the temporal limbus. The average collagen inclination remained predominantly parallel to the tissue surface at all depths. However, in the central cornea, the spread of inclination angles was greatest in the anterior-most stroma (reflecting the increased lamellar interweaving in this region), and decreased with tissue depth; in the peripheral cornea inclination angles showed less variation throughout the tissue thickness. Inclination angles in the deeper stroma were generally higher in the peripheral cornea, suggesting the presence of more interweaving in the posterior stroma away from the central cornea. An increase in collagen X-ray scatter was identified in a region extending from the sclera anteriorly until about 2 mm from the corneal centre. This could arise from the presence of larger diameter fibrils, probably of scleral origin, which are known to exist in this region. Incorporation of this quantitative information into finite-element models will further improve the accuracy with which they can predict the biomechanical response of the cornea to pathology and refractive procedures.
Highlights
The structure of the cornea and surrounding limbus is such that it is able to maintain its shape under the forces applied by intraocular pressure, the cardiac cycle and the extraocular muscles during eye movement
As the material mechanical characteristics of the human cornea are highly dependent on its fibrillar collagen arrangement, many studies have been carried out to determine the precise orientation and distribution of collagen in the corneal stroma
Using the latest developments in nonlinear optical high-resolution microscopy, Winkler et al [4] were able to quantify the angle of the out-of-plane collagen lamellae in the anterior 250 mm of the & 2015 The Authors
Summary
The structure of the cornea and surrounding limbus is such that it is able to maintain its shape under the forces applied by intraocular pressure, the cardiac cycle and the extraocular muscles during eye movement. Electron microscopy has shown that within the posterior stroma, collagenous lamellae (in which fibrils lie predominantly parallel to each other) appear to traverse the cornea from limbusto-limbus, remaining in-plane, parallel to the corneal surface. In the anterior third of the stroma, many lamellae do not remain in-plane, as there is frequent branching and interweaving of lamellae [1,2]. Using the latest developments in nonlinear optical high-resolution microscopy, Winkler et al [4] were able to quantify the angle of the out-of-plane collagen lamellae in the anterior 250 mm of the
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