Synthetic tissue substitute tied to high patch exposure, surgical revision in glaucoma patients

In patients with glaucoma, tube shunt implantation using a new synthetic tissue substitute, the CorNeat EverPatch, results in greater rates of patch exposure and surgical revision than using irradiated donor human cornea, reports a study.

“Our institution has terminated use of the EverPatch in conjunction with tube shunt implantation or revision surgery, and we recommend that surgeons carefully consider the rate of conjunctival complications when selecting patch graft material for surgical indications,” the researchers said.

Thirty consecutive patients who underwent ophthalmic surgery with implantation of the EverPatch at the Wilmer Eye Institute in Baltimore, Maryland, US, from February through August 2024 were included in this retrospective comparison study and biomaterial analyses of synthetic patch material. 

A comparison group consisting of 58 individuals who underwent ophthalmic surgery with implantation of irradiated donor cornea were matched 1:2 with patients receiving EverPatch based on age, surgeon, and type of glaucoma.

The researchers reviewed clinical electronic medical records of participants and analysed EverPatch, including its morphologic features, surface roughness, wettability, thermal ability, elemental analysis, and physical properties.

Of the patients who underwent surgery, 27 received EverPatch implantation during primary tube shunt placement, two during tube shunt revision, and one during covering of exposed suture used for scleral fixation of an intraocular lens. The rate of EverPatch exposure was 48.3 percent and that of surgical revision was 27.9 percent during the early postoperative period. [Ophthalmology 2025;132:799-814]

Among control participants, the rates of patch graft exposure and surgical revision were only 1.7 percent for both (p<0.0001 for all).

Notably, EverPatch devices formed a randomly aligned fibrous mesh with an average fibre diameter of 1.36 μm, surface roughness of 1.3 μm, pore size of 3.7 μm², and percent porosity of 37 percent.

“Explanted EverPatch devices demonstrated varying degrees of tissue integration with significantly increased wettability and changes in thermal stability and elemental composition,” the researchers said.

Alternative

The EverPatch is described as a “synthetic, tissue-integrating surgical matrix made of nonbiodegradable polymer fibres ... for implantation to reinforce sclera and aid the physical reconstruction of the ocular surface.” [https://www.accessdata.fda.gov/cdrh_docs/pdf22/K223074.pdf]

It is being marketed as an “alternative to natural irradiate human donor corneal tissue for long-term protection against exposure of ocular implants.”

However, the researchers found that the “overall exposure rate for EverPatch meterial ... was nearly 50 percent, and the return to the operating room rate for surgical explantation of the material and revision of the tube shunt was >25 percent.” Cases of wound leak, tube shunt device exposure, or infection did not occur.

On the other hand, the rates of graft exposure and surgical revision were <2 percent for irradiated donor human cornea among control participants. Such disparity is “striking” since the differentiating factor between groups was “the patch graft material,” according to the researchers.

“[T]he implant material must resist wear and corrosion, must minimize the foreign body response, and must facilitate tissue integration including conjunctival adhesion,” they said. “Thus, implantable device design, composition, mechanical properties, and architecture all are extremely important to consider and can affect clinical outcomes significantly.” [Drug Deliv Transl Res 2021;11:1675-1688]