A novel flexible microfluidic meshwork to reduce fibrosis in glaucoma surgery

Abstract

Purpose/RelevanceFibrosis and hence capsule formation around the glaucoma implants are the main reasons for glaucoma implant failure. To address these issues, we designed a microfluidic meshwork and tested its biocompatibility in a rabbit eye model. The amount of fibrosis elicited by the microfluidic meshwork was compared to the amount elicited by the plate of conventional glaucoma drainage device.MethodsSix eyes from 3 New Zealand albino rabbits were randomized to receive either the novel microfluidic meshwork or a plate of Ahmed glaucoma valve model PF7 (AGV PF7). The flexible microfluidic implant was made from negative photoresist SU-8 by using micro-fabrication techniques. The overall size of the meshwork was 7 mm × 7 mm with a grid period of 100 μm. Both implants were placed in the subtenon space at the supratemporal quadrant in a standard fashion. There was no communication between the implants and the anterior chamber via a tube. All animal eyes were examined for signs of infection and implant erosion on days 1, 3, 7, and 14 and then monthly. Exenterations were performed in which the entire orbital contents were removed at 3 months. Histology slides of the implant and the surrounding tissues were prepared and stained with hematoxylin-eosin. Thickness of the fibrous capsules beneath the implants were measured and compared with paired student’s t-test between the two groups.ResultsThe gross histological sections showed that nearly no capsule formed around the microfluidic meshwork in contrast to the thick capsule formed around the plate of AGV PF7. Thickness of the fibrotic capsules beneath the AGV PF7 plate from the 3 rabbit eyes was 90μm, 82μm, and 95 μm, respectively. The thickness at the bottom of fibrotic capsules around the new microfluidic implant were 1μm, 2μm, and 1μm, respectively. The difference in thickness of capsule between the two groups was significant (P = 0.002). No complications were noticed in the 6 eyes, and both implants were tolerated well by all rabbits.ConclusionThe microfluidic meshwork elicited minimal fibrosis and capsule formation after 3-months implantation in a rabbit model. This provides promising evidence to aid in future development of a new glaucoma drainage implant that will elicit minimal scar formation and provide better long-term surgical outcomes.

Ahmed implant coated with poly(2-methacryloyloxyethyl phosphorylcholine) inhibits foreign body reactions in rabbit eyes

“…First, the number of rabbits used in this study was relatively small. Nevertheless, we assume that even a small population is enough for a study for introducing a novel material, such as the previous study using three rabbits to test the biocompatibility of microfluidic meshwork in Ahmed glaucoma valve surgery [ 23 ]. Second, this was a short-term study involving a 4-week observation period.…”

“…Several studies have proposed different modifications to glaucoma drainage devices. The novel devices include an adjustable glaucoma device [ 19 ], a device delivering cyclosporine A [ 20 ] or MMC [ 21 ] for a certain period, and a device that contains a plate made of polymethyl methacrylate [ 22 ], or a plate replaced with microfluidic meshwork [ 23 ]. To our knowledge, this is the first preliminary study to demonstrate the use of a novel coating material for fibrosis inhibition in glaucoma implant surgery.…”

Rational Design of Microfluidic Glaucoma Stent

“…It has been shown that the appropriate choice of materials as well as the architecture of the GDDs can affect and reduce the postoperative development of fibrosis and scar formation [13,18,19]. A flexible microfluidic stent meshwork implanted in the subconjunctival space with channel sizes of cellular dimensions has demonstrated significantly less fibrosis development than the AGV PF7 in animal models [18].…”

“…It has been shown that the appropriate choice of materials as well as the architecture of the GDDs can affect and reduce the postoperative development of fibrosis and scar formation [13,18,19]. A flexible microfluidic stent meshwork implanted in the subconjunctival space with channel sizes of cellular dimensions has demonstrated significantly less fibrosis development than the AGV PF7 in animal models [18]. Although the basic mechanisms for fibrotic response and capsule formation around glaucoma drainage devices are not clearly understood, Amoozgar et al suggested that two implant-specific factors give rise to tissue reactions: (1) mechanical stress may develop at the interface between the tissue and the implant (e.g., due to a mismatch of mechanical properties) and (2) the implant disrupts the cellular and vascular system of the tissue [18].…”

A new glaucoma drainage implant with the use of Polytetrafluoroethylene (PTFE). A pilot study

“…Various methods have been used to halt the fibrosis formation, including the creation of a drug-coated device [ 5 , 6 ], intraoperative or postoperative anti-metabolite [ 7 , 8 ], subtenon steroid injection [ 9 ], and early start of aqueous suppressants [ 10 ]. Furthermore, modification of GDI’s material or design has always been tried [ 3 , 11 ]. Regarding the design, most GDI consists of a semirigid tube and a rigid and large reservoir.…”