Amanda Kiely Bicket, MD, MSE, discussed a new Gore glaucoma drainage implant (GDI) prototype that has been in development since 2017. In her symposium talk on Sunday, she described the possible advantages and the foundational preclinical work that will inform clinical trials.
The problem with the current GDI. “Published five-year failure rates are as high as 18% to 32%,” she said. Surgical complications sometimes require reoperation. “A frustrating amount of GDI failure is due to bleb fibrosis,” she added, noting that it has been attributed to aqueous humor factors and GDI geometry.
“What can we do about fibrosis leading to loss of bleb permeability?” she asked. The use of antifibrotics with GDIs is not really established, and staged surgeries require reoperation. The solution may be in the use of expanded polytetrafluoroethylene (ePTFE), Dr. Bicket said.
ePTFE: a versatile material. “If this is the first time you’re hearing about this project, glaucoma surgery now shares material in common not just with hernia mesh but also with the space program and your favorite hiking backpack,” she said.
Given its biocompatibility, biostability, and high compliance, the researchers hypothesize that an ePTFE device could result in physiologic tissue integration and a thinner, more permeable capsule. It could promote healing without exposure and would not need antifibrotics, mitomycin, or 5FU.
A new paradigm. “We are reengineering the tube-shunt bleb as an inflatable reservoir,” Dr. Bicket explained, in contrast to current devices where aqueous flows over a solid silicone plate.
Using ePTFE opens up new possibilities, she added, since it’s thin (100 micrometers) and is also bilayered. The prototype includes a pocket formed by two joined and sealed bilayers and a silicone tube leading into the reservoir. Aqueous can flow through the tube and reservoir and out to the integrated tissues. The design allows the external surface to be supported by an aqueous-permeable, cell-exclusion layer during tissue ingrowth. The prototype is more flexible than many other GDIs so it can be inserted taco-style and conforms to globe contours.
Encouraging preclinical work. The device is still in early stages, but the researchers are excited by preclinical trials in rabbits. The team compared the prototype with silicone Baerveldt-style implants as controls.
Collagen deposition is substantially less with the ePTFE device than with the control after one to three months, suggesting capsular integration. Furthermore, regardless of the inflated height, the prototype formed thinner blebs than silicone devices. Preclinical work also suggests that this new prototype is more permeable.
“We are particularly encouraged by the stability of the results for the ePTFE prototypes over three months in this aggressive healing and scarring rabbit model,” Dr. Bicket said.
Why should you be excited about this? The last two years set a foundational work for human clinical trials. The team recently received approval to begin recruiting patients outside of the United States and hope to share early clinical data in the Q2 or Q3 of 2023.
Financial disclosures: Dr. Bicket: W.L. Gore & Associates, Inc.: C.
Disclosure key: C = Consultant/Advisor; E = Employee; EE = Employee, executive role; EO = Owner of company; I = Independent contractor; L = Lecture fees/Speakers bureau; P = Patents/Royalty; PS = Equity/Stock holder, private corporation; S = Grant support; SO = Stock options, public or private corporation; US = Equity/Stock holder, public corporation For definitions of each category, see aao.org/eyenet/disclosures.
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