Office of Technology Transfer – University of Michigan

Magnetoelastic Actuator for Glaucoma Drainage Devices (MA-GDD)

Technology #6680

The use of glaucoma drainage implants has increased in recent years, especially relative to other surgical glaucoma procedures such as trabeculectomy. The increased utilization of drainage implants is related to a greater experience and appreciation of the efficacy of aqueous shunts, and a growing concern about late complications associated with standard filtering surgery. Glaucoma drainage devices are typically reserved for patients with severe uncontrolled glaucoma who have failed previous glaucoma surgery. In addition, the devices appear to be advantageous as a primary procedure in patients with a high likelihood of trabeculectomy failure, including neovascular and uveitic glaucomas. They are commonly used in the management of congenital and developmental glaucomas. Additional indications include traumatic glaucoma, aphakic and pseudophakic glaucoma, post-keratoplasty glaucoma, and other secondary glaucomas. Recently, interest has increased in using these devices as a primary surgical procedure for uncontrolled primary open-angle glaucoma.

Glaucoma drainage devices are designed to divert aqueous humor from the anterior chamber to an external reservoir, where a fibrous capsule forms about 4-6 weeks after surgery and regulates flow. These devices have shown success in controlling intraocular pressure (IOP) in eyes with previously failed trabeculectomy and in eyes with insufficient conjunctiva because of scarring from prior surgical procedures or injuries. However, the resistance to aqueous flow through glaucoma drainage implants occurs across the fibrous capsule around the end plate, and the major determinants of the final intraocular pressure are capsular thickness and filtration surface area1. The use of antifibrotic agents as adjuncts to drainage implant surgery has not proven effective in modulating capsular thickness. Valved implants appear to reduce, but do not eliminate, the risk of hypotony. Bleb encapsulation is more frequently seen with the Ahmed valve implant than other drainage implants

Magnetoelastic actuator for glaucoma drainage devices (MA-GDD)

The proposed solution is an enhancement to implantable glaucoma drainage devices (GDDs) aimed at reducing fibrosis and encapsulation that ultimately leads to loss of efficacy. While magnetoelastic materials show promise due to their wireless transduction capability, fabrication of complex 3D geometries and curvatures, remains challenging. This is especially important for implantable applications where such unusual shapes and curvatures are more likely to be necessary such as biomedical devices like the Ahmed glaucoma drainage device (AGDD).

The proposed actuators have customized geometries and 3D curvatures for actuation of liquid flow to prevent adhesion and facilitate removal of cells responsible for implant failure resulting from the development of a dense fibrous tissue around the device. The actuators are remotely excited to resonance with a magnetic field generated by external coils. Mechanical vibrations of the actuator would work to limit cellular adhesion to the implant surface that can otherwise lead to implant encapsulation and subsequent failure. The actuators are an amorphous magnetoelastic alloy that uses photochemical machining. The planar structures are annealed in 3D molds to provide the necessary curvatures. Flow velocities up to 250 μm/s are recorded at a wireless activation range of 25-30 mm, with peak actuator vibration amplitudes of 1.5 μm. Integrating actuators such as the ones described here have the potential to greatly enhance the effectiveness of glaucoma drainage devices at lowering eye pressure and can be useful in other areas of medicine as well.

Applications

  • Enhancement to Ahmed glaucoma drainage device for reducing fibrosis and encapsulation.
  • Any devices that requires wireless, magnetocelastic actuators with small form factors and low surface profiles over complex three-dimensional (3D) surfaces.

Advantages

  • Ability to prevent adhesion of cells that cause implant failure in glaucoma drainage devices.
  • Fabrication process allows for custom geometries of actuator
  • Can be adapted to any type of biomedical implant that requires magnetoelastic devices.

Publication: http://www.nature.com/articles/micronano201532