The effects of negative periocular pressure on intraocular pressure. (February 2020) - Ethier, C. Ross
Abstract: Glaucoma is a major cause of blindness, and IOP reduction remains the only clinically-validated therapy. In this study, we analyze a novel IOP-lowering strategy that uses a modest negative pressure (vacuum) applied locally to the periorbital region by a pair of goggles with each lens individually connected to a programmable pump. Motivated by clinical data showing an IOP reduction, we used an existing validated lumped-parameter model of the eye to understand the putative mechanism of this treatment. The model considers aqueous humor dynamics, episcleral venous pressure, and changes in ocular blood volume to describe how IOP changes with time in response to an external perturbation. We find that clinical data are qualitatively and quantitatively consistent with model predictions if we include two primary mechanisms in the model: first, negative pressure application causes a relatively rapid increase in globe volume accompanied by increased blood volume in the eye. Second, negative pressure application reduces episcleral venous pressure, causing a slower adjustment of IOP due to altered aqueous humor dynamics. These results provide testable hypotheses that hopefully will lead to a fuller experimentally-driven understanding of how negative periocular pressure influences IOP. Evaluating the long-term effects of such treatments on glaucoma patients requires further clinical study. Highlights: A novel strategy for IOP management has been recently proposed: patients wear goggles to deliver a modest negative pressure to the anterior globe and orbit. We used a lumped parameter mathematical model to investigate possible mechanisms of IOP lowering in this treatment. Model predictions are consistent with clinical data if we include ocular blood volume changes and reduction of episcleral venous pressure. The long-term benefit for vision preservation of goggle wear remains to be determined, but these results motivate further clinical studies.