Magnetically actuated glaucoma drainage device for regulating intraocular pressure after implantation

Abstract

Purpose : The key risk factor for glaucoma is increased intraocular pressure (IOP). Glaucoma drainage devices have been developed to reduce IOP and thus stop disease progression, however, the lack of proper IOP control can lead to serious postsurgical complications. To have a better control of the IOP, we are developing an innovative magnetically actuated glaucoma implant with a hydrodynamic resistance that can be adjusted following surgery.

Methods : Our smart implant is comprised of a drainage tube and a housing element in which a magnetic “micro-pencil” valve is integrated (Figure 1A and B). The implant is made from poly(styrene-block-isobutylene-block-styrene), or ‘SIBS’.The magnetic microvalve was fabricated from SIBS containing homogeneously dispersed iron microparticles. “Micro-pencil” valves of this material were fabricated by replica molding using hot embossing, with femtosecond laser-machined fused silica glass molds (Figure 1C). The same technique was used to fabricate the housing element.

Results : Microfluidic experiments involving actuating the magnetic micro-pencil with a moving external magnet were carried out to confirm the valving function. The pressure upstream the implant, which would correspond to the IOP, was measured while the microvalve switched between open/closed states (Figure 2A). A pressure difference up to 10 mmHg was achieved which is sufficient to overcome hypotony, i.e. too low IOP (Figure 2B).

Conclusions : The femtosecond laser machining process has proved to be an effective technique to fabricate the molds for both the microvalve and the glaucoma device. The features in these molds were successfully transferred to a thermoplastic material like SIBS. Microfluidic experiments performed with the novel, magnetically actuated glaucoma implant have shown that, when in the closed state, the microvalve can provide a sufficient hydrodynamic resistance that can help to overcome hypotony.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Figure 1: A – Placement of the magnetically actuated glaucoma implant in the eye. B – Schematic depiction of the magnetically adjustable glaucoma implant design and actuation mechanism of the integrated micro-pencil valve. C – Schematic illustration of the micro-pencil valve fabrication process.

 

Figure 2: A – Setup used for the microfluidic experiments. B – In vitro measurement of the pressure variation up-stream the device as a result of the valve operation.