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Computational fluid dynamics simulations of aqueous flow through the CyPass ® Micro‐Stent
Author(s) -
Vidal Aroca F.,
Vera L.F.,
Missel P.,
Sarangapani R.
Publication year - 2017
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2017.0s047
Subject(s) - trabecular meshwork , sclera , glaucoma , aqueous humor , ciliary muscle , outflow , materials science , ophthalmology , biomedical engineering , glaucoma surgery , medicine , optics , physics , accommodation , meteorology
Purpose In normotensive eyes, aqueous humor is eliminated through Schlemm's canal and through the iris root in approximately equal fractions. But in glaucomatous eyes, the hydraulic resistance of the trabecular meshwork restricts outflow through the canal and causes the IOP to rise. The CyPass ® supraciliary micro‐stent is a device implanted by minimally invasive glaucoma surgery ( MIGS ) which is designed to reduce IOP by allowing an alternative pathway for aqueous humor outflow. The device, a fenestrated polyimide tube, is inserted between the sclera and the ciliary muscle creating an adjacent fluid space which communicates directly with the suprachoroidal outflow pathway. Methods To better understand and illustrate the mechanism of action for this device, computational fluid dynamics simulations of aqueous flow were conducted in human eye models with and without implanted devices. The configuration of the device and fluid space in the eye was obtained from a separate mechanical simulation of device implantation using an explicit solver. Hydraulic resistances of the vitreous and sclera were obtained from the literature. Results The resistances of the trabecular meshwork and ciliary muscle were adjusted to produce an IOP of 24.4 mmHg (the mean untreated IOP in the COMPASS trial) and a suprachoroidal elimination fraction of 80%. With the device implanted the hydraulic resistance of the fluid in the space adjacent to the device was reduced ~4 orders of magnitude to achieve the post‐surgical IOP of 16.8 mmHg observed in the COMPASS study. It was found that the device reduces IOP by decreasing the overall resistance of the eye to hydraulic flow by more than 30%. Conclusions The model confirms that substantial IOP lowering is achievable through aqueous egress via a supracilliary stent even when there is substantial trabecular resistance.