Equilibrium shape of the aqueous humor-vitreous substitute interface in vitrectomized eyes

Purpose: To predict the shape of the interface between aqueous humor and a gas or silicone oil (SO) tamponade in vitrectomized eyes. To quantify the tamponated retinal surface for various eye shapes, from emmetropic to highly myopic eyes. Methods: We use a mathematical model to determine the equilibrium shape of the interface between the two fluids. The model is based on the volume of fluids (VOF) method. The governing equations are solved numerically using the free so ware OpenFOAM. We apply the model to the case of idealized, yet realistic, geometries of emmetropic and myopic eyes, as well as to the real geometry of the vitreous chamber reconstructed from magnetic resonance imaging (MRI) images. Results: The numerical model allows us to compute the equilibrium shape of the interface between the aqueous humor and the tamponade fluid. From this we can compute the portion of the retinal surface that is effectively tamponated by the fluid. We compare the tamponating ability of gases and SOs. We also compare the tamponating effect in emmetropic and myopic eyes by computing both tamponated area and angular coverage. Conclusion: The numerical results show that gases have better tamponating properties than SOs. We also show that, in the case of SO, for a given filling ratio the percentage of tamponated retinal surface area is smaller in myopic eyes. The method is valuable for clinical purposes, especially in patients with pathological eye shapes, to predict the area of the retina that will be tamponated for a given amount of injected fluid.