Droplet Laplace valve-enabled glaucoma implant for intraocular pressure management

Abstract

Glaucoma, the leading cause of irreversible blindness worldwide, is closely linked to aqueous overaccumulation and elevated intraocular pressure (IOP). For refractory glaucoma, aqueous shunts with valves are commonly implanted for effective aqueous drainage control and IOP stabilization. However, existing valved glaucoma implants have the disadvantages of inconsistent valve opening/closing pressures, poor long-term repeatability due to their reliance on moving parts, and complex architectures and fabrication processes. Here, we propose a novel valving concept, the droplet Laplace valve (DLV), a three-dimensional printable moving-parts-free microvalve with customizable and consistent threshold valving pressures. The DLV uses a flow discretization unit governed by capillarity, comprising a droplet-forming nozzle, and a separated reservoir to digitize continuous flow into quantifiable droplets. Unlike the classic one-time-use Laplace valves, the DLV's unique design allows for its reusability. The opening pressure is adjustable by varying the nozzle size, like the classic Laplace valves (following the Young–Laplace equation), while the closing pressure can be modified by tuning the separation distance and the reservoir size. Various DLVs with customizable opening pressures from 5 to 11 mmHg have been demonstrated, with opening/closing pressure differences suppressed down to <0.5 mmHg (<0.15 mmHg under the best conditions). Thanks to its moving-parts-free nature and digitized flow properties, the DLV shows a highly repeatable valving performance (<1.7%, 1000 cycles) and a predictable linear flow rate–pressure correlation (R² > 0.99). Preliminary ex vivo validation in an enucleated porcine eye confirms the DLV's efficiency in aqueous shunting and prompt IOP stabilization. The DLV technology holds great promise in glaucoma implants for IOP management and various microsystems for flow control.