Biomechanical Relationships Between the Aqueous Veins and Perilimbal Sclera During Intraocular Pressure Regulation

A major assumption of microinvasive glaucoma surgeries (MIGS) is that effective intraocular pressure (IOP) reduction can be achieved by enhancing aqueous humor (AH) outflow into the aqueous veins. However, this IOP outcome is not predictable in part due to lack of knowledge concerning the role of tissue biomechanics on AH outflow through the distal aqueous veins within the perilimbal sclera (PLS). The purpose of this study is to investigate the biomechanical response of the aqueous veins and the PLS and their interaction during IOP.

Optical resolution photoacoustic microscopy were implemented to capture the 3D deformations of the aqueous veins and in the surrounding PLS during aqueous outflow in porcine and human whole globes. Partial trabeculotomy was performed to minimize the contribution of the trabecular meshwork to the outflow resistance.

The deformations of the tissue components and the IOP were measured in both porcine and human eyes. Strong correlations were found among the relative cross-sectional area of the aqueous veins, strains in the PLS in porcine eyes, and the steady-state (SS) IOP of porcine eyes.

The data shows that stiff PLS restricts vein cross-sectional area and results in overall higher SS IOP in an eye.

The findings in this study suggest the potential for predicting the limit of effectiveness of an MIGS given knowledge of the interactive behaviors of the aqueous veins and PLS in an eye.