Development and characterization of a nano-structured glaucoma shunt

Abstract

Purpose : Hypotony following glaucoma filtering surgery can be prevented by using small lumen shunts that limit fluid outflow. Electrospinning is a promising platform for the development of shunts, as it allows for incorporation of almost any polymer and/or therapeutic moiety into nano or microfibers that can be configured into devices of various dimensions and conformations. We hypothesized that electrospinning can be used to fabricate small lumen shunts that prevent post-operative hypotony.

Methods : Electrospinning was used to manufacture shunts with an internal diameter of 50 µm, and composed of polyethylene terephthalate (PET) nanofibers. Size and morphology were characterized via scanning electron microscopy. Fluid flow through shunts of varying diameter and length at different flow rates was modeled using the Hagen-Poiseuille equation (HPE). In vitro fluid flow experiments were conducted using a syringe pump, and the pressure change was measured using a manometer. Biocompatibility was evaluated through histology of shunts implanted in rabbit eyes for 14 days (N=3). Intraocular pressure (IOP) was monitored for 25 days in normotensive rabbits with the proximal end of either a closed (N=3) or open shunt (N=3) implanted in the anterior chamber and distal end implanted in the subconjunctival space. Shunt patency was evaluated 25 days after placement in rabbit eyes (N=3).

Results : Modeling predicted that a 6 mm long, 50 µm inner diameter shunt could provide for significant IOP reduction at physiologically relevant flow rates. PET shunts had wall thickness of 350 ± 15 µm, length of 5, 6, or 7 mm, and 50 µm inner diameter created by removal of a 50 µm diameter template wire. In vitro experiments revealed that the HPE accurately predicted the flow of phosphate buffered saline through PET shunts, and that shunts were leak-proof and maintained structural integrity after one week. Shunts implanted in rabbit subconjunctival tissue elicited a reaction comparable to silicone tubing from a commercial glaucoma drainage implant (GDI). Post-operative hypotony was not observed following in vivo placement and shunts remained patent in vivo.

Conclusions : Electrospinning provides a suitable platform for development of biocompatible shunts that are durable, leak-proof, relegate fluid flow according to the HPE, and prevent post-operative hypotony in vivo.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.