Healing of LASIK flaps

Kamma, Christina-Stamatia. 2007. Healing of LASIK flaps. PhD Thesis, Cardiff University.

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Abstract

The aim of this study was to obtain a better understanding in the healing of LASIK-like flaps using an in vitro organ culture method in bovine corneas. At early stages of the PhD, during protocol optimisation, a 5mm trephine was used to injure bovine corneas. At later stages a custom-made eye holder was used to induce LASIK-like incisions in corneas. Immunohistochemistry for a-smooth muscle actin (aSMA) and cytokeratin was used to monitor myofibroblast and epithelial cell expression, respectively, during the wound healing process. Additionally, the effect of certain cytokines (i.e. TNFa, Fas ligand, TGF-Pi and IL-la) was tested in terms of corneal transparency, myofibroblast expression and tissue mechanical strength during the healing process. The later series of experiments was an attempt to manipulate and improve wound healing after LASIK. Healing in this in vitro system closely followed the effects that are already known from the literature. In addition, preliminary evidence on the cytokine corneas proved that there is a correlation between cytokine type and concentration with the effect in tissue transparency, extend of wound healing response and tissue mechanical strength. X-ray diffraction also provided important information about collagen ultrastructural changes in the corneas during the healing process. Parameters such as fibrillar diameter, spacing, distribution and orientation were studied. Collagen fibrillar diameter and spacing remained constant for control corneas during the organ culture time-span, indicating that this in vitro system does not induce any swelling effects on the tissue. However, injured corneas became significantly swollen (p<0.05) during culture. Swelling effects were more severe in trephined corneas than in LASIK-like injured ones. However, collagen fibrillar diameter remained normal in the periphery of injured corneas, but it increased significantly in areas within and around the wound in trephined samples and in the flap incision site for LASIK-like ones. In both types of wounding, collagen orientation changes were observed and were associated with the process of creating the injury. However, in the case of trephine wounded corneas, tissue swelling and changes in collagen orientation reflected the processes of tissue repair. These differences will determine corneal stability and strength follow trauma and, possibly, refractive surgery. The transparency of the cornea depends on both the collagen and the interstitial proteoglycans. In order to obtain a better insight in ultrastructural changes during the wound healing process molecular modelling techniques were used in order to construct a theoretical model for the core protein of biglycan. This molecule is a dermatan sulphate proteoglycan and its numbers increase up to seven times during wound healing. It is considerably larger than the rest of proteoglycans and molecular modelling also revealed numerous potential collagen interaction sites.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Biosciences Optometry and Vision Sciences
Subjects:	R Medicine > RE Ophthalmology
ISBN:	9781303209468
Date of First Compliant Deposit:	30 March 2016
Last Modified:	12 Feb 2016 23:12
URI:	https://orca.cardiff.ac.uk/id/eprint/54605

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