The human eye works through a perfect balance between fluids and moving parts. The clear fluid inside, called aqueous humor, pushes gently on the colorful iris. This delicate balance is a perfect example of Fluid-Solid Interaction (FSI). This process is very important because it controls the pressure inside your eye and helps you see clearly. Any problems with this balance can lead to serious diseases like glaucoma, where high intraocular pressure (IOP) damages vision. A Human Eye FSI CFD simulation is a powerful tool for doctors and engineers. It lets them see exactly how the fluid moves and how the iris responds without any risk to a patient. Understanding these Aqueous Humor Dynamics helps in designing better treatments and medical devices, like artificial lenses. This report uses the methods from a research paper [1] to show how a Human Eye (Aqueous Humor and Iris) FSI Fluent simulation works.

• Reference [1]: Wang, Wenjia, et al. “Fluid and structure coupling analysis of the interaction between aqueous humor and iris.” Biomedical Engineering Online15 (2016): 569-586.

Figure 1: A schematic of the human eye, showing the aqueous humor and iris, based on the reference paper for this FSI CFD analysis [1].

Simulation Process: FSI Modeling, Geometry, Meshing, and Solver Setup

First, we created a 3D model of the front part of the eye using Design Modeler. The model includes the cornea, the lens, and the iris. This simulation uses a 1-way Fluid-Solid Interaction (FSI) model. This means we first solve for the fluid’s behavior and then apply those results to see how the solid part reacts. We used two programs: ANSYS Fluent to calculate how the aqueous humor flows and ANSYS Structural to see how the iris deforms under the fluid’s pressure. The material properties for the iris, like how stiff it is, were all taken from the reference paper [1] to make the simulation realistic.

Figure 2: The 3D geometry used in this Ocular Biomechanics Simulation [1].

Post-processing: CFD-FSI Analysis, Visualizing Iris Deformation and Aqueous Humor Flow

The pressure contour provides a clear, professional visual of how the aqueous humor pushes on the eye’s internal structures. Our simulation shows a clear pressure difference, ranging from a high of 3,640 Pascals at the top to a low of 3,370 Pascals at the bottom. This small pressure difference is what drives the fluid to circulate gently inside the eye. The deformation contour shows the direct result of this pressure. The fluid pushes down on the iris, causing it to bend by a very small but important amount, up to 0.000108 meters. This is the “Solid” part of the Fluid-Solid Interaction, and it shows exactly how the eye’s tissues respond to the internal fluid pressure.

Figure 3: Pressure distribution and total deformation from the Human Eye FSI Fluent analysis, showing how fluid pressure causes the iris to move.

The velocity contour shows how this pressure difference makes the fluid move. The flow is very slow, with a top speed of only 0.0000745 m/s. Instead of flowing straight, the fluid creates gentle, swirling patterns called vortices. These slow swirls are very important because they help deliver nutrients to parts of the eye that do not have their own blood supply. This professional visual demonstrates the complete FSI process: the fluid pressure causes the iris to deform, and this interaction ensures the fluid circulates correctly to keep the eye healthy. The most important achievement of this simulation is the successful use of a one-way FSI model to accurately show how the fluid pressure of the aqueous humor directly causes the iris to deform, providing a critical tool for understanding the biomechanics of eye diseases like glaucoma.

Figure 5: Velocity field from the Aqueous Humor Dynamics Fluent analysis, showing the gentle vortices necessary for a healthy eye.