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Paul Missel, Ramesh Sarangapani; Comparing the predicted efficacy of one versus two supraciliary micro-stents for lowering IOP in glaucoma patients using an ocular computational fluid dynamic model. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2057.
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© ARVO (1962-2015); The Authors (2016-present)
Clinical Studies have shown a single supraciliary micro-stent (CyPass®, MS) implanted with cataract surgery lowers IOP in glaucoma patients. Before undertaking clinical studies to evaluate the potential benefit of implanting more than one MS, a computational model was developed to simulate MS implantation and to compare the IOP lowering effect of one or two MS.
A computational multi-physics model representing an average human eye incorporated physiologic mechanical and hydraulic properties, enabling simulation of device implantation and fluid flow/pressure in the entire eye with or without an implanted MS. Ocular geometries were constructed representing eyes with 0, 1 or 2 MS. Aqueous humor was treated as a simple fluid, all other tissues were modeled using porous flow. Tissue dimensions and hydraulic resistances to flow for sclera and vitreous were taken from the literature. Hydraulic resistance of trabecular meshwork and ciliary body were adjusted to reproduce the pressure and outflow characteristics of normal and glaucomatous eyes. The resistance of the suprachoroidal space was held very low consistent with free movement of fluid in this space.
Structural simulations reproduced clinical OCT images of the conformation of the device and of a tented fluid space allowing unobstructed fluid flow between the aqueous humor and supraciliary space. While qualifying the model using pre- and post-treatment IOP measurements from implanting a single device from the COMPASS clinical trial, it was determined that a single MS enables the IOP to drop to within <0.2 mm Hg of the suprachoroidal pressure. In fact it was possible to use the qualifying data to establish a power law relationship between pre-treatment IOP and suprachoroidal pressure, an important parameter of the model.
Since a single MS is able to allow the IOP to equilibrate with the suprachoroidal pressure, there would no additional benefit provided by implanting a second MS.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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