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Lamellar orientation in human cornea in relation to mechanical properties

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Bibliographic Details
Title:	Lamellar orientation in human cornea in relation to mechanical properties
Authors:	Boote, Craig¹ bootec@cf.ac.uk, Dennis, Sally¹, Huang, Yifei², Quantock, Andrew J.¹, Meek, Keith M.¹
Source:	Journal of Structural Biology. Jan2005, Vol. 149 Issue 1, p1-6. 6p.
Subjects:	Cornea, Connective tissues, Extracellular matrix proteins, Collagen
Abstract:	Abstract: 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° 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. [Copyright &y& Elsevier]
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Database:	Engineering Source

Description
Abstract:	Abstract: 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° 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. [Copyright &y& Elsevier]
ISSN:	10478477
DOI:	10.1016/j.jsb.2004.08.009