Design, development and evaluation of electrospun, nano-structured microshunts for controlled intraocular pressure (IOP) reduction

Abstract

Purpose : Despite advances in glaucoma drainage implant design, hypotony and fibrosis remain major clinical challenges. Electrospinning is a versatile manufacturing process which utilizes electrostatic forces to produce polymeric nanofibers. Here, we utilize electrospinning to manufacture two novel microshunt designs with a biodegradable inner core to test the hypothesis that inner core degradation would allow gradual inner diameter (ID) expansion, regulate aqueous humor outflow, and avoid hypotony while enabling significant IOP reduction.

Methods : Shunt dimensions were selected based on modeling using the Hagen-Poiseuille equation to safely and significantly lower IOP. Polymer composition and fabrication techniques were chosen to allow shunts to conform to the eye. Two designs of pressure control shunts (PCS) were electrospun with a patent, 75 µm lumen surrounded by a 25 µm thick inner core of degradable polyglycolic acid nanofibers, surrounded by an outer layer of non-absorbable polyethylene terephthalate nanofibers (PCS1: length: 6 mm; outer diameter (OD): 421 ± 8 µm and PCS2: length: 9 mm; OD: 350 ± 11 µm). PCS size and morphology were characterized via scanning electron microscopy. PCS1 (n=3) and PCS2 (n=3) were implanted into New Zealand White rabbits with the proximal end in the anterior chamber and the distal end in the subconjunctival space. IOP, shunt patency, bleb morphology and biocompatibility were evaluated for 28 days after implantation.

Results : A mean IOP reduction from baseline of 32% was achieved in the PCS1 group IOP as compared to 27% in the PCS2 group 28 days after implantation. Hypotony was not observed in any rabbits in either group. Bleb morphology was sustained and indicated patency and consistent aqueous humor outflow in both groups throughout the post-operative period. Shunts were patent in all (n=3) eyes that received PCS2 and 2 out of 3 eyes that received PCS1 28 days after implantation.

Conclusions : PCS designs regulate aqueous humor outflow via a degradable inner core that prevents post-operative hypotony and ultimately expands to provide additional IOP reduction.

This is a 2020 ARVO Annual Meeting abstract.

 

(A) Predictive modelling showed that PCS designs were capable of controlled IOP reduction. (B) PCS1 and PCS2 showed safe, effective, and durable IOP lowering and maintenance. (C, D) PCS1 and PCS2 sustain bleb morphology indicating consistent aqueous drainage.