Understanding the basis of corneal shape and transparency

Boguslawska, Patrycja Joanna 2012. Understanding the basis of corneal shape and transparency. MPhil Thesis, Cardiff University. Item availability restricted.

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Abstract

Corneal transparency is a feature that can be explained by the regular arrangement of collagen fibrils and proteoglycans across the whole tissue. This special assembly promotes destructive interference of scattered light and allows only the light going forward to pass through the corneal stromal layers. There are four proteoglycans (PGs) occurring in corneal stroma: decorin, lumican, mimecan, and keratocan. Thanks to their negative charges they make a hydrated interfibrillar gel around collagen fibrils so that the fibrils do not touch each other. However, the way the proteoglycans interact with collagen to promote this spacial arrangement is not known. The first model described in this thesis was achieved from 3-D reconstruction of the tissue. We compared our results with bovine and mouse cornea and reached the conclusion that they are not arranged in any special order around the collagen fibrils. However, they are found in sufficient number in the corneal stroma to be responsible for corneal transparency. We decided to compare our results from the human to the fish cornea to get more general view of the corneal structure. The fish is known to have smaller and more closely spaced fibrils than human. The curvature of the cornea is different as the function of these two tissues is different. Fish is more flat, while the human is more spherical. The lamellar arrangement also differs between these animals. The fish cornea is more circular, while the human is orthogonal. The fibril diameter and collagen spacing is increasing towards the end of these both corneas and following on from this the transparency is reduced as we go to the periphery. We also had a chance to examine guinea pig corneas as a model of Climatic Droplet Keratopathy – a disease which is related to the loss of corneal transparency. They are similar to the human cornea in terms of the demand for ascorbic acid which is responsible for protection against UVB. The results confirmed our assumption: the animals fed on low ascorbic acid diet demonstrated some structural changes connected with UVB radiation.

Item Type:	Thesis (MPhil)
Status:	Unpublished
Schools:	Optometry and Vision Sciences
Subjects:	R Medicine > RE Ophthalmology
Uncontrolled Keywords:	cornea, corneal transparency, electron microscopy, collagen, proteoglycans, 3D reconstruction
Date of First Compliant Deposit:	15 August 2023
Last Modified:	15 Aug 2023 12:37
URI:	https://orca.cardiff.ac.uk/id/eprint/49913

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