Magnetically actuated glaucoma drainage device for regulating intraocular pressure after implantation

Abstract

The key risk factor for glaucoma is increased intraocular pressure (IOP). Glaucoma drainage devices implanted in the eye can reduce IOP and thus stop disease progression. However, most devices currently used in clinical practice are passive and do not allow for postsurgical IOP control, which may result in serious complications such as hypotony (i.e., excessively low IOP). To enable noninvasive IOP control, we demonstrate a novel, miniature glaucoma implant that will enable the repeated adjustment of the hydrodynamic resistance after implantation. This is achieved by integrating a magnetic microvalve containing a micropencil-shaped plug that is moved using an external magnet, thereby opening or closing fluidic channels. The microplug is made from biocompatible poly(styrene-block-isobutylene-block-styrene) (SIBS) containing iron microparticles. The complete implant consists of an SIBS drainage tube and a housing element containing the microvalve and fabricated with hot embossing using femtosecond laser-machined glass molds. Using in vitro and ex vivo microfluidic experiments, we demonstrate that when the microvalve is closed, it can provide sufficient hydrodynamic resistance to overcome hypotony. Valve function is repeatable and stable over time. Due to its small size, our implant is a promising, safe, easy-to-implant, minimally invasive glaucoma surgery device.

Droplet Laplace valve‐enabled glaucoma implant for intraocular pressure management

“…In the test, 0.9 wt% saline was used as the working fluid, and a 20 μL/min flow rate was infused into the enucleated eye's anterior chamber until the system was stabilized. Notably, the used infused rate was much higher than the physiological secretion rate of the aqueous humor, to effectively balance the leakage of the aqueous humor throughout the eye and stabilize the anterior chamber, which was consistent with previous studies for ex vivo testing 13,14 of enucleated eyes. After that, the DLV was closed by manually clamping the connecting tube with a binder clip, to induce pressure buildup inside the anterior chamber and simulate an ophthalmological hypertensive condition.…”

“…The artificial subconjunctival space‐targeting glaucoma implants are currently predominant 5,6,10,11 . Among them, passively valved subconjunctival implants remain the most accepted aqueous shunting devices, mainly due to their superior pressure management performance in reducing complications like hypotony (i.e., low IOP) when compared to the nonvalved implants, 12 in addition to the structural simplicity and higher patient compliance compared to the actively valved counterparts 13,14 . Passively valved glaucoma implants that have been used in the clinic include the Krupin and Ahmed® glaucoma valves.…”

“…5,6,10,11 Among them, passively valved subconjunctival implants remain the most accepted aqueous shunting devices, mainly due to their superior pressure management performance in reducing complications like hypotony (i.e., low IOP) when compared to the nonvalved implants, 12 in addition to the structural simplicity and higher patient compliance compared to the actively valved counterparts. 13,14 Passively valved glaucoma implants that have been used in the clinic include the Krupin and Ahmed ® glaucoma valves. The Krupin implant, introduced in 1976, features a slit valving mechanism, 15,16 in which the aqueous shunting tube's distal end is equipped with horizontal and vertical slits, creating deformable flaps that function as the valving components.…”

Microfluidics in the eye: a review of glaucoma implants from an engineering perspective

“…10g. 208,234 The micro-pencil contains homogeneously dispersed magnetic microparticles and thus its fluidic channels can be opened or closed using an externally controlled magnetic stimulus. Preliminary in vitro tests have shown that the IOP difference between the closed and open state is about 6 mmHg under a flow rate of 2.5 μL min −1 and an outlet pressure of 5 mmHg, which is sufficient to overcome hypotony.…”