Detailed 3D micro-modeling of rat aqueous drainage channels based on two-photon imaging: simulating aqueous humor through trabecular meshwork and Schlemm's canal by two-way fluid structure interaction approach.

Elevated intraocular pressure (IOP) appears to have a broader impact on increased resistance to aqueous humor (AH) outflow through the conventional aqueous outflow system (AOS). However, it is still unknown how AH drainage resistance is produced or why it becomes increased in glaucoma. It is hard to accurately obtain hydrodynamic parameters of AH within the trabecular meshwork (TM) outflow pathway tissues based on current technology. In this study, we reconstructed the rat AOS model with high-resolution two-photon imaging, and simulated the AH outflow process. The resolution of the two-photon imaging system can be up to 0.5 μm for imaging the AOS tissues. Quite a few morphological parameters of rat TM in conditions of normal and elevated IOP were determined using the experiment integrated with the simulation method. We determined that the TM thickness is 49.51 ± 6.07 μm with an IOP of 5.32 kPa, which significantly differed from the TM thickness of 66.4 ± 5.14 μm in the normal IOP group. Furthermore, 3D reconstruction of local aqueous drainage channels from two-photon microscopy images revealed detailed structures of the AOS and permitted the identification of 3D relationships of Schlemm's canal, collector channel, and trabecular drainage channels. An algorithm of finite element micro-modeling of the rat TM outflow pathways reveals the importance of TM for mechanical performance, with the potential to assist clinical therapies for glaucoma that seek to steer clear of an abnormal TM.