The impact of fluid mechanics on wound healing after glaucoma surgery
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    The impact of fluid mechanics on wound healing after glaucoma surgery
    Project Description

    Glaucoma is a neuro-degenerative disease of the optic nerve and is the second leading cause of blindness world-wide. Glaucoma prevalence is estimated to be 70 million world-wide with 7-million blinded from this disease. (1) Glaucoma affects 300,000 Australians with 25,000 visually impaired. Prevalence increases with increasing age and population studies have shown that 10% of Australians over the age of 80 have glaucoma. This prevalence is set to double by the year 2025 due to the aging population. The total annual health cost to Australia in 2005 (direct and indirect) was $1.9 billion per annum. This is set to increase to $4.3 billion by 2025. The need for a robust and cost effective means for improving surgical outcomes is clear. This is particularly true in many developing countries where, for logistic reasons, glaucoma surgery is the only viable therapeutic option.

    Elevated intraocular pressure is a major risk factor for glaucoma development and progression. Treatments which reduce intra-ocular pressure (IOP) are effective in delaying vision loss. Successful glaucoma surgery is more effective than laser or medical treatment at lowering intraocular pressure, although the risk of complications largely due to unpredictable wound healing responses have generally led to surgery being the final option.

    Glaucoma surgery lowers intraocular pressure by providing a conduit for aqueous humor to exit the anterior chamber of the eye into the subconjunctival space, thus bypassing outflow obstruction in the trabecular meshwork, which is the principle cause of IOP elevation in glaucoma. Aqueous humor collects in the subconjunctival space to form a bleb. From here, fluid is absorbed through the bleb wall or taken up by surrounding blood vessels to leave the eye. Surgery is usually performed by creating a guarded fistula (trabeculectomy) or with a glaucoma drainage device where a plate acting as a spacer is placed in the subconjunctival tissues and connected to the anterior chamber by a tube. A number of alternative drainage devices have been developed that attempt to drain aqueous humor through routes other than the subconjunctival space but none of these to date have been subject to rigorous investigation or enjoy widespread use. The wound healing response in the subconjunctival tissues after trabeculectomy and glaucoma drainage device surgery is similar.

    Excess scar formation in the subconjunctival tissues is the principal cause of surgical failure. Post-operative wound contraction and scar formation increase resistance to aqueous outflow with IOP elevation consequent to a:

    1. Reduction in the bleb surface area available for aqueous absorption.
    2. Reducing the porosity of the bleb wall as determined by the thickness of the bleb wall and the maturation of the scar tissue.
    3. Reducing in the volumetric absorptive capacity of the surrounding tissues.
    To avoid future surgical failure we have constructed a computational model of the eye-tissue system. This model consists of several sub-models linked together by the underlying requirement of fluid conservation. These sub-models include fluid production from the ciliary body within the eye itself, the volume/pressure response of the eye, the fluid removal from the eye via the trabecular meshwork and uveo-sclearal routes (in both normal and diseased states), fluid removal from the eye via the tube-shunt, any prosthesis and a poro-elastic model of the fluid movement into, and sorption by, the peri-orbital tissues. The model has identified several key processes which need to be further understood and so model development is currently being coordinated with experiments performed by our collaborators Professor Jonathan Crowston and Associate Professor Michael Coote.

    Staff

    Grants
    • 2009-2011, NHMRC, Regulating fluid mechanics to improve the outcome of glaucoma surgery, Jonathan Crowston, Michael Cootes, Bruce Gardiner, David Smith, $269,250.
    Publications  

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School of Computer Science & Software Engineering
Faculty of Engineering, Computing & Mathematics
The University of Western Australia
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Last updated: July 15 2015 09:16:55.