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R. I. Angunawela, A. Azarbadegan, I. Eames; Theoretical Prediction of the Relationship Between Pressure and Time Taken to Express All Fluid From the Donor-Host Interface in Endothelial Keratoplasty. Invest. Ophthalmol. Vis. Sci. 2010;51(13):785.
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© ARVO (1962-2015); The Authors (2016-present)
Endothelial keratoplasty is an evolving technique for transplantation of a new layer of endothelial cells onto the posterior surface of the cornea. Currently this layer is attached by filling the anterior chamber with air, which is pressurised to over 35mmhg for up to 8 minutes, during which time the new endothelial layer is pressed up against the posterior cornea. Adhesion between the graft and host are thought to occur through molecular forces rather than through endothelial pump function. These adhesion are likely to occur rapidly once the graft-host interface has been emptied of fluidWe aimed to determine the theoretical relationship between intraocular pressure and time taken to remove all fluid from the interface between the graft and posterior cornea
A lubrication analysis based on a constant pressure over the cornea and a spatially uniform separation was applied to understand how the fluid layer between the donor cornea and host is squeezed out. We assumed that the endothelial layer was smooth, had a diameter of 8.5 mm and an initial interface separation of 100 microns and the liquid was water.
Fluid in the interface is squeezed out by the bouyancy forces of the intraocular bubble and not directly by intraocular pressure. Bubble size is related to pressure.The thickness of the liquid layer decreases as the inverse of the square root of time and the inverse of the square root of intraocular pressure.
The fluid layer from the graft host interface decreases initially rapidly (to about ~ 5 microns) after 1 minute (at a pessure of 50mmhg) after which any further decrease is proceeds relatively slow. This occurs within 2 minutes at a pressure of 25mmhg.Assuming that molecular adhesive interactions occur fairly rapidly between the graft and host, current times for maintaining the eye at high pressure may be significantly reduced.
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