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Farah Abdelhafid, Giovanna Guidoboni, Sangly P Srinivas; Impact of convection currents on drug distribution in the anterior chamber: a computational study. Invest. Ophthalmol. Vis. Sci. 2020;61(7):3465.
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Intracameral implants are being investigated for sustained drug delivery to treat glaucoma and intraocular inflammation. Convection currents of the aqueous humor (AH) in the anterior chamber may vary with posture and temperature and consequently should affect drug pharmacodynamics. In this study, we investigate the effect of convection currents by means of a computational model.
AH is modeled as a heat-conducting Newtonian viscous fluid whose motion is driven by (i) inflow/outflow conditions in correspondence of the posterior chamber/trabecular meshwork, (ii) temperature difference between the body (Tb) and the external ambient (Te). Standing, supine and prone positions are simulated by changing the orientation of the gravitational acceleration. The drug implant is placed at the drainage angle and segmental AH flow is neglected. Once released, the drug dynamics is assumed to be determined by advection-diffusion equations, where the advective part is influenced by AH flow. The mathematical problem is solved via Finite Elements (FreeFem++) in two-dimensional geometry.
Drug distributions are simulated for different values of Tb, Te and postures. Simulations show that changes in temperature and posture change dramatically affect the fluid dynamic structure of AH flow in the anterior chamber, with the presence of one central vortex (standing) or two primary vortices (supine, prone) and with motion potentially changing direction. Consequently, the drug dynamics in the anterior chamber may vary significantly depending on temperature and posture.
We have developed a simulation platform for examining the drug distribution by an intracameral implant in the anterior chamber. The simulations show that temperature and posture induce changes in AH flow that influence drug dynamics. The main limitation is that our simulation is currently for 2D geometry and requires to be extended for 3D. In addition, modeling of the impact of the flow currents near the implant will have to be included.
This is a 2020 ARVO Annual Meeting abstract.
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